IT iconb TECTONICS BLOG Rev. 2024-04-04

Gregory Charles Herman, PhD, Flemington, New Jersey, USA

The structure of lunar, multi-ringed astroblemes with tectonic implications for Mars and Earth.

Introduction * Review * Geographic maps of eighteen lunar astroblemes  * Seismological aspects * The South Pole - Aitken basinMaria Imbrium and Serenetatis * Mare Nectaris * Mare Crisium * Mare Orientale * Mars and Earth modelsDiscussion References * GE Pro Moon KMZ file


Click on an image to enlarge it

Two large bolide strain fields mapped on the North American tectonic plate using GE Pro
North American Chicxulub and Chesapeake impact effects
Figure 1.
ITFF crustal-strain fields mapped around two large impact craters on the North American tectonic plate.  Circumferential blast patterns drawn around each crater include strain sectors dominated by compression  and reverse faulting (C - down range), tension and normal faulting (T - up range), or mixed-mode (M) faulting within lateral sectors. Radial arching of the lithosphere is traced around each crater at 660, 1600, and 2900-km radii. The compressed foreland has thickened upper mantle and crust downrange of the crater where grounded impact energy is focused and refracted back to the surface at great distances. Crustal seismogenic zones mapped inside 90oN to 90oS latitudes and 30oE to 150oW longitudes mapped by Herman (2006). Mapped basins and uplifts mapped from Trehu and others (1989), Pindell and Kennon (2009), and Ewing and Lopez (1991). LU – Llano uplift. CP – Colorado Plateau. ETOPO1 surface base theme from Amante and Eakins (2008).

Anatomy of an astrobleme
Figure 2
Large, km-scale meteorite impacts on Earth produce enormous amounts of grounded shock energy resulting in far-field strains in the upper mantle and crust reaching thousands of kilometers distance from craters.  Experimental results from impact tests using small glass balls and seismological ray paths for compressional body waves (P-waves) help constrain the geometry of planetary-scale impact-tectonic, far-field (ITFF) strains (adapted from Herman, 2022). The Earth model is part of a SU Pro CAD model.

Target and projectile impact parameters
Oblique impact parameters

Figure 3. Model impact parameters for an oblique impact including a missile, target, impact point (O) and impact crater. AO is horizontal to ground surface at the impact point, CO is vertical, BO is the missile trajectory (impact angle Θ = 70o). Four equidimensional blast sectors include two up- and down range ones and two lateral ones split along the plane of trajectory. Real blast sectors are disproportional and skewed by impact obliquity and inherited compositonal and structural heterogeneity of target materials. Headings are horizontal in the plane of trajectory measured down range relative to geographic north.

Fracture strikes, patterns, and strain areas from glass-ball impact tests conducted at high (>60°), intermediate, and low (<30°) angles

Test 1 fault histograms

Glass-ball impact results

Test 2 fault histogramsFigure 4. The results of 2019 impact tests using a hardened-steel projectile fired from a .177-caliber air pistol into 60 mm - diameter glass balls (Herman, 2022). Impact angles ranged from 38° to 85° degrees. The glass ball used in the highest-energy impact test is pictured at the bottom right of the middle diagram along with the resulting strain field. This impact produced antipodal cracks, and a profile depiction of its down-range strain field stemming from refracted energy is shown at the top of figure 2. The lower panel includes circular histograms of strikes of radial fractures with the concentric ones omitted (yellow lines). As the impact obliquity decreases, radial fractures rotate from high-angle, double-shear, conjugate fractures bisected by the projectile heading to those striking normal to the heading for low-angle impacts.

Lunar chronology and Apollo anorthosite sample 600025

Moon chronology

Apollo 16 sample 60025

Figure 5. Top - Lunar chronology including large impact basins with temporal placement and symbols scaled to outer-ring diameters (table 1). Twelve of the largest basins mapped in figure 6 are represented, most of which are thought to occur during a Nectarian and Early Imbrium period of heavy bombardment (~3.8 to 3.9 Ga). Basin ages and bombardment-rate curve adapted from Tartèse and others (2019) and Stöffler and Ryder (2001). Note the clustering of ages of the oldest impact melts and the oldest gneiss on Earth. 1 Age of the SPA from Morbidelli and others, 2012). The open circle labeled “V” represents  the Vredefort impact crater (2.2 Ga), the oldest confirmed impact crater on Earth (Allen and others, 2019).  Bottom - Apollo 16 surface sample 600025 photomicrograph and facts.

Table 1.
Locations, sizes, and interpreted headings of eighteen lunar astroblemes (fig. 5). Cells highlighted gray fall within +10% deviation of calculated ring dimensions using a Ö2 scaling ratio for adjacent rings. This ratio suits 64% (9/14) of outer rings 4 to 6, 33% (12/36) of inner rings 2 and 3, and 42% overall (21/50).
Table 1

The structure of eighteen lunar astroblemes in geographic space using eleven geospatial themes

6A. NASA Digital Terrain ModelGeographic digital terrain model

6B. Structures and GeosamplesGeological structures and samples

6C. GRAIL Free-Air Gravity
Free-air gravity

6D. GRAIL Bouguer Gravity
Bouguer gravity

6E. Bouguer Gravity (Watters, 2022)Bouguer grvavity map from Watters (2022)

6F. JAXA SELENE Magnetic-Field Intensity
Magnetic-field intensity

6G. NASA LP Spectroscopy - Silicon
Silicon Spectroscopy

6H. NASA LP Spectroscopy - Aluminum
Aluminum spectroscopy

6I. NASA LP Spectroscopy - Iron
Iron spectroscopy

6J. NASA LP Spectroscopy - Potassium
Potassium spectroscopy

6K. NASA LP Spectroscopy - Uranium
Uranium spectroscopy

6M Circular histograms of large-bolide headings
Meteorite heading histograms

Figure 6.  Top - Eighteen multi-ring astroblemes mapped in geographic space using 11 geospatial themes. Maps include a colorized NASA DTM (5A), GRAIL free-air (5B) and Bouguer (5C) gravity, large faults and geosamples (D, a Bouguer gravity gradient map (5E) by Watters (2002), SELENE magnetic-field intensity (5F), and LP spectroscopy themes of elemental abundances in shallow ground for silicon (5G), aluminum (5H), iron (5I), potassium (5J), uranium (5K) and thorium (5L).  Each multi-ring structure is labeled and includes concentric rings of variable radii corresponding to radial and concentric crustal features and ITFF strain limits. Ring dimensions and bolide headings summarized in table 1. Rings radii labeled for the Aiken and Mare Imbrium basins.  Outer ring radii labeled for all other basins. NASA and JAXA data sources explained in the text. The orange line labeled SPA limits and large-basin limits are interpreted boundaries used for calculating basin and astrobleme areas. Bottom - Interpreted bolide headings are statistically tallied and compared to large-bolide headings mapped on Mars.

Lunar cross section including seismological traces of refracted and reflected shock energy
Moon cross section
Figure 7.
 A Moon profile and aligned seismic-velocity profile adapted from Weber and others (2011) used to  model interior phase boundaries. Mantle and crustal regions having energetic shock-wave rarefaction reflections are highlighted yellow. The outer rings of some impact basins correlate well with shock reflections of 60° arising from material-phase boundaries with  inverted acoustic impedances like the upper- and lower-mantle boundary (fig. 8; Telford and others, 1976). 

Seismic-wave energy coefficients vs. wave-incidence angles for reflected and transmitted compression waves

Seismic energy partitioningFigure 8.  Graph adapted from Telford and others (1976, fig. 4.18) of compression-wave energy coefficients versus incidence angles for partitioning compression-wave energy at layer boundaries of contrasting densities. Most shock energy is transmitted across layers having increased density contrasts at incidence angles less than 60°. But most of the seismic energy is reflected off all boundaries at high incidence angles above 80°. The most reflected energy is focused at a 60° incidence angle for  boundaries having decreasing densities and compression-wave velocities (inverted acoustic-impedance contrast).

Lunar seismic-compression-wave reflection geometry in the upper mantle
Seismic rarefaction waves

Figure 9.  
Compression-wave refraction and reflection paths for the Moon’s crust and upper mantle at 30°, 45°, and 60° incidence angles. P-wave refractions follow those of Wieczorek (2009).  Note how head waves reflected off phase boundaries with negative impedance contrasts give rise to rarefaction waves that return to the surface with diminished energy but first-arrival tension that induces normal, brittle failure and localized upper-mantle melting along crustal faults.

The South Pole - Aiken Basin (SPA)South Pole - Aiken BasinSouth Pole - Aiken BasinSouth Pole - Aiken BasinFigure 10. The SPA basin portrayed in GE Pro using ten geospatial themes. Top pair includes NASA LOLA DEM (left) and Bouguer Gravity by Watters (right; 2022). Middle pair is SELENE magnetics (left) and GRAIL free-air gravity (right). The bottom panel includes a stock GE Pro surface image and NASA LP spectroscopy for silicon, aluminum, iron (wt. %) and potassium and uranium (ppm). The blue stippled area along longitude W180° is a 5° data gap that is explained in the text. CA - Mare Crisium antipode, IA - Mare Imbrium antipode, SA - Mare Serenetatis antipode. AC1 - Aitken basin center of Hurwitz and Kring (2014). AC2 - Aitken basin 890-km radius center ring center.

Maria Imbrium and SerenitatisMaria Imbrium and SerentatisMaria Imbrium and SerenitatisMaria Imbrium and Serenitatis spectroscopyFigure 11. Maria Imbrium and Serenitatis portrayed in GE Pro using ten geospatial themes. Top pair includes NASA LOLA DEM (left) and Bouguer Gravity by Watters (right; 2022). Middle pair is SELENE magnetics (left) and GRAIL free-air gravity (right). The bottom panel includes a stock GE Pro surface image and NASA LP spectroscopy for silicon, aluminum, iron (wt. %) and potassium and uranium (ppm). Geosamples locations noted.

Mare Nectaris
Mare NectarisFigure 12.  
A GE Pro portrait of the Mare Nectaris astrobleme overlapping an earlier one using the NASA blue steel DTM (left), JAX SELENE magnetic-field intensity (middle), and GRAIL free-air gravity intensity (right). This astrobleme displays axial splitting with a type, double-shear fault response. It likely was of moderately high obliquity and northwest heading. It marks the base of the Nectarian lunar period before the late-heavy bombardment period. Ring radii marked in kilometers.

Mare CrisiumMare CrisiumFigure 13. A GE Pro portrait of the Mare Crisium astrobleme using the NASA blue steel DTM (left), JAX SELENE magnetic-field intensity (middle), and GRAIL free-air gravity intensity (right). This astrobleme also displays axial splitting and of moderately high obliquity and eastward heading. Earlier faults from Mare Nectaris are crosscut by Mare Crisium as seen in the circular histogram.

Mare Orientale
Mare Orientale
Mare Orientale
Mare Oriental cross section
Figure 14.
Mare Orientale in GE Pro (top) and cross section (bottom). Top maps include the NASA Blue Steel DTM (left) and the GRAIL free-air gravity themes (right). above maps using GE Pro stock imagery (left) and the Watters (2012) Bouguer gravity theme (right). Bottom diagrams include an E-W cross  section of the Mare Orientale basin above diagrams of Moore (1976) illustrating maps and profiles of craters formed by oblique missile strikes.

Lunar impact tectogenesis
Lunar impact tectogenesis
Figure 15.  
Profile diagrams of lunar, upper mantle and crustal ITFF strains, and a large igneous province stemming from impact tectogenesis that includes ring dikes intruded along concentric faults. A structural solution to having KREEP terrane registered spectroscopically on the lunar surface is to have deep-seated upper mantle and crustal faults bringing uppermost-mantle layers to the surface downrange of a large, oblique impact from rapid, reverse faulting and uplift stemming from focused, refracted shock energy.

Cone, cup, and saucer reflection ITFF geometry
Cone, cup, and saucer strain -field
Figure 16.  
A SketchUp Pro 2022 CAD Moon model illustrating two overlapping sets of ITFF strain models comprising the South Pole -Aitken Basin astrobleme. This event involved a low- to moderate angle, very large, fragmented bolide with multiple projectiles having formed a vast strewn field including the Aiken basin where down-range upper-mantle wedging occurs from refracted, radial faulting that's overprinted by reflected rarefaction structures (fig. 17).

SUP CAD model of the SPA and Maria Imbrium, Serenitatis, and Nectaris overlapping astroblemes occupying opposite hemispheres.
CAD Moon model
Figure 17.
 A SUPCAD model of the Moon includes structural details of the SPA and three other large astroblemes occupying the opposite hemisphere that include Maria Imbrium, Serenitatis, and Nectaris (fig. 18)The SPA is modeled with two impact centers, the more northerly having formed by spalling of the parent bolide forming the South Pole crater. Together they constitute an enormous impact strewn field. Low-intensity gravity anomalies peppering the Aitken basin downrange of the South Pole are likely secondary craters formed during this event.

Three overlapping lunar astroblemes comprising Oceanus Procellarum
Three overlapping astroblemes
Figure 18.
 Maria Imbrium, Serenitatis, and Nectaris are three of the largest lunar astroblemes that overlap in close proximity on the Moon's nearside with ITFF strains that cut across and interfere with one another. A SU Pro model in semi-transparent mode is used to demonstrate the spatial alignment of mapped upper mantle and crustal faults caused by refracted and reflected shock-waves arising from the acoustic boundary between the upper and lower mantle. This surface has an inverted impendance contrast for compression waves that gave rise to rarefaction (pressure-release) waves that incited near-surface material failure under tension and upper-mantle magmatism from decompression melting. Igneous plutons intruded along the concentric, tensional faults correlate with localized high-intensity gravity flares. The shock-wave reflection geometry resembles cones and tea cups with saucers.  The left two diagrams are overhead views of the overlapping astroblemes whereas the right diagram is a side view illustrating a cross-section perspective of the structural interference using the reflected 30o and 60o compression-wave models (fig. 16).

Lunar tidal locking
Lunar tidal locking

Figure 19.  The Moon's heavy side has the densest concentration of mass (mascons) and always faces Earth. It's locked into orbit with Earth so that it spins once on its polar axis for each lunar orbit with its 'near side' always facing us. This is called tidal locking and explains why we only directly see half of the lunar surface. It also gives a spatial perspective on the powerful yet subtle gravitational forces operating over vast distances in space.

A SUP CAD Mars model
Mars seismic model

Figure 20.  A SUP 2022 Mars model incorporating the seismological constraint on interior layering and the mantle regions where shock rarefaction reflections occur relative to a large impact crater. The major velocity inversion at about 1500 km depth at the boundary between the plastic mantle and liquid core is a major reflective surface. Reflections of 30° to 60° incidence angles are highlighted yellow and correspond spatially with the surface extents of Mars' largest astroblemes at about 2500 km radius.

A satellite-derived gravity-intensity map of Mars centered on the Syria-Sinai-Solis Planums astrobleme

The Martian Syria-Sinai-Solis planums astrobleme

Figure 21.
A satellite-derived gravity map of Mars centered on the Syria-Sinai-Solis planums astrobleme with rings mapped around the crater at the radial dimensions of reflected shock waves rising off the outer core at 30° to 60° reflection angles (fig. 19). This structure clearly represents the effects of down-range, fan-shaped crustal wedging occurring opposite to up-range extension faulting where the associated Olympus Mons and Tharsis Montes LIPS occur. The projectile headings are southeast along the yellow lines. The base gravity theme is from Genova and others (2016). Additional geospatial details of this massive structure are provided in Herman (2022).

A SUP CAD Earth model

Earth seismological layering

Figure 22.  
A SU Pro 2022 Earth model incorporating the seismological constraint on interior layering and the mantle regions where shock rarefaction reflections occur relative to a large impact crater. The major velocity  inversion at about 2900 km depth at the boundary between the plastic mantle and liquid core is a major reflective surface. Reflections of 30° to 60° incidence angles are highlighted yellow and correspond spatially with the surface extents of Earths' largest astroblemes at about 5000 km radius.
A satellite-derived gravity-intensity map showing the ringed structural nature of the suspected Congo basin astrobleme The Congo Basin astroblemeFigure 23.  A satellite-derived, gravity-intensity theme for Earth made for GE Pro portraying the crustal and upper-mantle stains centered on the Congo basin, Africa. The 5000-km radius ring around the basin center corresponds to the 60o rarefaction reflection off the core-mantle boundary that directly aligns with the Triassic Newark rift basins hosting the central Atlantic magmatic province (CAMP; fig. 23) and the southern oceanic-spreading ridges framing Africa. This is also when Pangaea began splitting apart with India, North America, and Australia drifting rapidly away.

Stylized map reconstruction of Pangaea near the start of the Mesozoic Era showing how CAMP and continental rifting could have been spurred by a suspected bolide impact forming the Congo basin

Pangaea at about 201 Ma

Figure 24.  
A paleo-continental reconstruction of the supercontinent Pangaea adapted from Yoshida and Hamano (2015) showing the location of CAMP down range from the suspected Congo basin impact crater (~201 Ma?).

I recently proposed punctuated tectonic equilibrium as an alternative tectonic theory to uniformitarianism after mapping impact-tectonic far-field (ITFF) crustal and upper-mantle strains in many astroblemes on Earth and Mars using global physiographic, gravity and magnetic geophysical themes, geographic information systems (GIS) and three-dimensional (3D) virtual globes (figs. 1 and 2; Herman, 2022). The ITTF strains are global tectonic components arising from impact tectogenesis; when catastrophic, large-bolide (asteroid or comet) impacts suddenly disrupt a terrestrial bodies' crust and upper mantle during episodes of projectile bombardment and mass accretion. However the manner in which shock stresses are absorbed and dispersed within the target body were underdeveloped then for shock strains stemming from reflected energy because of my initial focus on refracted shock strains after recognition of foreland ITFF compressive strains occurring down range from the Chesapeake (35.5 Ma) impact on the eastern seaboard of north America (fig. 1). This work therefore advances the geometry and structural effects of reflected shock energy as part of the finite strains on terrestrial bodies resulting from impact tectogenesis. The lunar surface and interior are first portrayed with 2D and 3D illustrations including seismological constraints that limit the geometric solutions for where reflected shock energy is focused to produce ITFF strains. The multi-ring astroblemes (impact structures) of the Moon are measured and placed into context with the interior layering to show how km-scale bolides impacting the lunar surface at hypervelocity speeds have produced numerous, large, multi-ring astroblemes having strain components stemming from both refracted and reflected shock energy. Two of the largest impact events, the South Pole - Aitken Basin and Mare Imbrium ones, have played significant roles in lunar geological evolution by generating regional melt bodies upon impact that included major phases of mineral-differentiation and fractionation resulting in the formation of the bright, silicon-rich, anorthositic highlands surrounding concentrations of dark, iron-rich mare (ma-aire); the high density, mafic admixture of impact-melted and reconstituted crust and upper mantle stemming from impact tectogenesis. The Moon lacks an atmosphere and plate tectonics, so its surface geology stems from extraterrestrial bombardment and gives the clearest picture of ITFF strains manifest by targeted terrestrial bodies.  

The seismological constraints from the lunar study are then applied to profile illustrations of Mars and Earth that spatially constrain regions around large terrestrial impact craters subject to focused shock strains. This work is done using geographic information systems (GIS), the Sketch Up (SU) Pro computer-aided 3D drafting system (CAD) and Google Earth Pro (GE Pro). It is an exercise in analytical geometry rather than numerical modeling, and structural insights are gained from applying empirical results obtained from missile-impact tests (Moore, 1976), from both traditional (Telford and others, 1976) and atomic-bomb seismology (Dienes and Fisher, 1961), and from prior geological analyses of the lunar surface (Wilhem and others (1987) and Watters and others (2022) among many others).

The concept of tectonic inheritance was also raised in the aforementioned work because ITFF strain fields stemming from different impacts overlap to form interfering surface structures with deep roots in terrestrial bodies.  An astrobleme imposes structural heterogeneity in a target body that subsequently perturbs the shock responses made by subsequent impacts with superimposed strain fields. Many ITFF structures also exhibit planar geological symmetry with respect to impacts striking at oblique angles and producing down-range crustal wedging and thickening opposed to up-range crustal rifting where large tensile faults give rise to the sudden, concurrent production of magma in deep reaches from dynamic decompression (figs. 1 to 3). Mantle melting occurs along ITFF faults in both radial and concentric alignment to craters that mediated magmatic ascent into the crust to form large igneous provinces spurred by impact tectogenesis.

I begin by mapping and profiling the structural layering and seismological nature of the Moon to gain a spatial perspective on how refracted and reflected impact-shock energy produced its large impact basins and ITFF multi-ring surface structures. Structural details for eighteen multi-ring astroblemes are mapped using eleven geospatial themes to demonstrate how impact tectogenesis produced the contrasting physiography of the bright lunar highlands with the dark mare flooring deep, centralized impact basins that together constitute the face of the Old Man of the Moon. The largest lunar impact basins are portrayed as vast astroblemes where upper mantle and crustal layers have been melted, plasticized, and brecciated around craters with crustal compaction and thickening down range of oblique projectile strikes and tensional rifting up range and circumferential to craters with the latter stemming from reflected shock waves. LIP production apparently occurs in ways conforming to these two, incremental, ITFF strains mechanisms with recognizable seismological behavior and structural interference.


Figure 3 summarizes key geometric impact parameters used to characterize interpreted bolide or missile trajectories including the surrounding blast quadrants, angle of impact, and principal axis of compressive stress. Oblique impacts display symmetry with respect to the plane of trajectory as opposed to vertical impacts that are axis symmetric with more equally distributed radial strains given a homogeneous target (Monteux and Arkani-Hamed, 2019). I also demonstrated both axis and plane-symmetric impact strain fields in little glass spheres with a bench-top impact experiment that used a steel projectile fired from an air gun into the glass balls at oblique impact angles ranging between 35° and 85° (fig. 4; Herman, 2022). In the most energetic impact test set at a very steep impact angle, a down-range structural tongue was produced from absorbed shock energy that has a structural form resembling the geometry of refracted elastodynamic compression (P) waves arising from near-surface seismic sources in Earth’s crust (fig. 2). This experiment helped constrain the geometry of down-range, foreland ITFF crustal wedging and thickening seen at the regional scale for Earth and Martian astroblemes, but it didn’t adequately explore the possibility of reflected impact-shock energy contributing to the ITFF concentric faulting and crustal welting around large impact craters. Outboard crustal arching, intra-plate seismic zones and crustal drift of the North American tectonic plate (NAP) point to ITFF concentric welting including active intra-cratonic seismogenic zones that define sub-plate boundaries in North American lithosphere relative to the Chicxulub crater (fig. 1). The ITTF welting includes epierogenic arches and intervening troughs or moats that together form low-amplitude lithospheric waveforms having amplitudes on the order of few kilometers. These radial, curved structures are large mountain ranges and sedimentary basins that likely formed by impact tectogenesis. A good example of this is where southern most Mexico and the Central American isthmus arose from the seas along the 2900-km arch developed around the Chesapeake impact (fig. 3). The focus here is on exploring how grounded shock energy arising from large-bolide impacts is manifest in the upper layers of the Moon, Earth, and Mars. I use computerized geological models that are constrained by geophysical principles to illustrate how target bodies are layered, and how those layers systematically dispel impact shock waves resulting in ITFF regional strains including radial and concentric crustal faulting, concentric lithospheric welting and large-igneous provinces (LIPS).

The bench-top impact experiments of Herman (2022) using 60 mm glass balls and a hardened steel projectile displayed systematic variability of the strain-field areas with respect to impact obliquity, and the typical development of conjugate, secondary, brittle structures bracketing the crater that varied in their extent and density with respect to gentle (<30°), intermediate (30° - 60°), and high (>60°) impact angles when measured from the spherical surface (fig. 4). The geometry and area of each strain field varied with impact angle such that the near-normal impact has a circular shape and axial symmetry whereas those formed by moderate to shallow impact angles developed planar symmetry across the plane of trajectory (figs. 3 and 4). The moderate-angled impacts produced fan shaped strain fields, and impacts at the shallowest angle having the largest faults flaring out in lateral sectors in a direction normal to the impact headings (fig. 4). These forms are referenced below to help interpret an astroblemes impact obliquity, but impact angles are not tallied in table 1 owing to the high levels of uncertainty in their interpretations. More impact testing into spherical surfaces is necessary in order to derive statistically valid reference models more certain ones. Large crustal fault striking in conjugate arrangement bracketing an impact strewn field were also noted in the structural analysis of thirteen Martian astroblemes using remote sensing (Herman, 2022). The most notable aspect of these impact experiments and mapping exercises was the production of a down-range, fractured wedge from refracted shock energy that was focused downward within the target along the line of impact momentum (fig. 2). The structural tongue descends into the foreland blast sector where the focused energy was refracted back to the surface almost one-quarter of the surface span away from the crater. The downrange wedging stems from uniaxial compression of the targeted media and opposes the up-range sector where tensile fracturing occurs after the crust is first compressed, then stretched behind the down-range sector like that seen on Mars for the Syria-Sinai-Solis Planums astrobleme and up-range volcanism.

Sequential impact-generated shock events on a planetary surface gradually hardens its exterior from repeated bombardment producing overlapping, far-field strains exhibiting tectonic inheritance (Herman, 2022). In other words, pre-existing geological heterogeneity of a terrestrial body will influence the seismological expression of absorbed energy and hence structural expression of successive, overlapping strain fields. But the ITFF strains occurring as regional, large-scale, epierogenic welts are poorly understand and their geodynamic mechanisms ill defined. I therefore attempt to address these aspects below by first mapping and parameterizing eighteen multi-ting lunar impact basins, and then using a 3D Moon model to portray seismologically constrained, geometric solutions for the shock strains stemming from km-scale bolide impacts resulting in multi-ring terrestrial astroblemes. Impact tectogenesis must also include the geological processes and sets of secondary structures leading to the formation of the lunar highlands where thickened crustal regions having elevated gravity intensities likely reflecting the spurred emplacement of basic- to granitic plutons along secondary faults and and mineral veins lying beneath impact-generated regolith and distal ejecta blankets that radiate outward beyond the crater for hundreds to thousands of kilometers distance (fig. 6 and Willhelms and others, 1986). Widespread epeirogeny, or the pronounced vertical tectonic shifts that have been noted since the advent of geology as a science, are placed into geospatial perspective below with the natural, but extraterrestrial-born, impact-tectonic agents of bolide bombardment and accretion that are integral agents of solar system evolution.

With respect to the Moon, much of its geologic history is gained by studying the distribution and structural expression of large, multi-ring astroblemes across its surface and from geological analyses of about one-third ton of surface samples and core collected on the near side by the U.S.A, Russia, and Chinas' manned and unmanned missions (figs. 5 and 6, and table 1). According to Wilhelms and others (1987) impacts began to leave a visible record about 4.2 billion years ago (Ga), after the crust and mantle had differentiated and the crust had solidified. At least 30 basins and 100 times that many craters larger than 30 km in diameter were formed before a massive impact created the Nectaris basin about 3.92 Ga. Impacts continued during the ensuing Nectarian Period at a lesser rate, whereas volcanism left more traces than during pre-Nectarian time. The latest basin-forming impacts created the giant and still-conspicuous Imbrium and Orientale basins during the Early Imbrian Epoch, between 3.85 Ga and 3.80 Ga. The rate of crater-forming impacts continued to decline during the Imbrian Period. Beginning in the Late Imbrian Epoch, mare-basalt flows remained exposed because they were no longer obscured by many large impacts. The Eratosthenian Period (3.2-1.1 Ga) and the Copernican Period (1.1 Ga to present) were times of lesser volcanism and a still lower, probably constant impact rate. Copernican impacts created craters whose surfaces have remained brighter and topographically crisper than those of the more ancient lunar features. But so far, no direct sampling has occurred on the far side.
As impact craters increase in size, they become increasingly complex and change from having central peaks or groups of peaks to having central depressions surrounded by two or more mountainous rings (Hartmann and Kuiper, 1962). This transition occurs for structures exceeding about 180 to 300 kilometers in diameter with the latter regarded as impact basins. More than thirty multi-ring astroblemes are identified on the Moon as these structures shape the lunar surface (Willhem and others, 1987; Fasset and others, 2012; Tartèse and others, 2019; among many others). Eighteen of the largest and most apparent multi-ring impact structures are mapped in figure 6 with the corresponding ring radii and interpreted heading parameters recorded in table 1.

Hartmann and Wood (1971) provide a thorough review and synthesis of geological thought surrounding multi-ring impact basins of the Moon during the first decade of lunar exploration. Ideas for ring genesis ranged from frozen crustal tsunamis to collapse faulting from propagating standing waves, but they end their summary with the statement “stresses will be set up in the Moon by the violent dissipation of energy during basin formation; all authors agree that these stresses are likely to produce a series of concentric ring fractures surrounding the basin, through the detailed theoretical models differ.” A recurring aspect of this early work is the recognition of both concentric and radial fault systems, the former of which has been characterized as having a √2 ratio for inter-ring spacing (Hartmann and Wood, 1972). This is predicated on the assumption that circular plates sagging into an underlying fluid medium will fracture at distances near a √2 radius values based on the theoretical and experimental work of Lacke and Onat (1962).

The Moon lacks plate tectonics but has a long history of impact tectogenesis (fig. 5). It was likely born from an impact of proto Earth by a planetesimal about 4.5 billion years ago and its evolution since then includes continuous meteorite bombardment that added mass to its body (Hartman and Davis, 1975). Vast surface regions have been pulverized and melted from the heat and energy absorbed from the largest impacts. Upon the initial hardening and density stratification of its shell from an early, lunar magma ocean (LMO), the Moon was subsequently pounded by large projectiles during the formative stages of the solar system as the planets and their moons were settling into place. A hypothetical, late-heavy bombardment (LHB) phase early in the lunar chronology depicted in figure 5 from about 3.7 to 3.9 Ga is proposed to have been spurred by the orbital adjustments of the four largest planets that destabilized near-Earth asteroids resulting in a period of path clearing and heavy bombardment that apparently focused on the near side for the Moon with probable, coeval periods of impact tectogenesis on Earth and Mars (Gomes and others, 2005). But as Harrison and others (2018) and Boehnke and Harrison (2016) have pointed out, the most widely used evidence to support the LHB hypothesis yields unreliable impact histories but does not preclude the existence of such events.

Lunar multi-ringed astroblemes were instrumental in the development of Melosh and McKinnon’s’ (1978) ring tectonic theory that explains how large, concentric fault scarps develop around large impact craters from the transient collapse of a crater rim inwards and downwards from gravitational adjustments toward the crater center shortly after impact. The structural process involves a rigid, but weakened crust and lithosphere sitting atop fluid or ductile substrate that allows mantle flow from beneath to accommodate rigid fault slip and block rotations in response to gravitational instabilities. This is the only theory available at this time to account for the formation of ringed basins, and many numerical simulations have been run to test this theory under a wide range of conditions using variable impactor size, crustal thickness, and near-surface thermal gradients that reproduce similar results with empirical observations (Potter, 2015). But by their own admission they have not been able to reproduce model results that consistently agree with observed ring-spacing geometry using these methods. Currently, the computational time and fidelity of the numerical simulations can only be tested for impacts occurring normal to the surface and in two-dimensions. Three dimensional simulations including variable impact obliquity have not been attained. But my fundamental concern with ring-tectonic theory is the assumption of having a fluid layer below the crust to allow rapid creep of the mantle material that accommodate the differential movement of overlying solid fault blocks. Perhaps melting of the upper mantle immediately upon impact temporally provide the fluid substrate needed to accommodate crustal extension, but according to the lunar seismic data, there is no fluid substrate beneath the Moon’s crust showing seismic shear-wave dampening. The first apparent, internal seismological boundary in the upper mantle having reduced S-wave velocities occur at about 230 km depth but accompany increased P-wave velocities. This upper-mantle acoustic boundary therefore likely stems from mineral-phase transitions involving crystalline anisotropy that retard S-wave transmissions but are denser with more rapid P-wave velocities. The first noticeable acoustic-layering contrast in the upper mantle occurs at a depth of about 490 km and separates the upper and lower parts of the mantle with an inverted impedance contrasts for compression waves (figs. 7 to 9).

Very large impacts also produce widespread ITFF strains in the form of radial and concentric faulting and folding with the consequential development of large igneous provinces (LIPs) fed by deep-penetrating faults that mediate the ascent and dispersal of mantle-derived basic lava covering large areas like surface areas like Oceanus Procellarum (fig. 6). Material ejected from impact basins has also been distributed over vast surface reaches and provide useful markers in analyzing a meteorite's horizontal heading and the geologic history of the Moon (Wilhelm and others, 1987; among others). For example, if a crater or other structure is superimposed, or formed on top of such ejecta, then the crater is younger than the impact basin. On the other hand, if a feature is partially buried by the ejecta blanket, the feature must be older than the impact basin. By analyzing stratigraphic superposition and cross-cutting structures across the Moon, it is possible to derive a relative overview of the lunar geological history that is partly constrained with absolute radiometric dating of collected surface samples of mostly loose material, regolith, and boulder fragments (figs. 5 and 6).
We know from the NASA Grail mission that the lunar crust ranges in thickness from near zero from excavation around cratered areas to over 60 km thick in the lunar highlands (Miljkovic, 2018). Planetary geologists generally use the starting assumption that the excavation depth of a cratering event is about 10% of the excavated diameter (Melosh, 1989; Melosh and Ivanov, 1999). If we use a average crustal thickness of 30 km for the Moon, then upper-mantle excavation and mixing occurs for astroblemes with inner rings exceeding 300 km diameter. As detailed below, only the five largest lunar astroblemes exceed this size. Very large, deep craters are floored by mare, melted crust + upper-mantle material. Mare is ponded within the cratered, central regions of large impact basins (fig 6). This also happens sometimes on Earth (French, 2004). Mascons are circular, high-intensity gravity anomalies where ponded mare is concentrated (Phillips and others, 1997). Sampled lunar basalts have an average crustal density of ~ 3.3 gm/cm3, whereas the bulk Moon crust is ~ 2.95 gm/cm3 owing to the abundant plagioclase feldspar in anorthosite-rich crust of the lunar highlands that is comparatively light and thick with respect to mare.

Geophysical and structural aspects of eighteen large, lunar astroblemes

Global geophysical themes have proven very useful in demonstrating ITFF strains occurring in radial alignment around large craters as part of planetary astroblemes, or ‘star wounds’ (Dietz, 1962; Buthman 2022; Herman 2022). Eighteen large impact basins displaying multi-ring architecture are listed in table 1 from the largest to smallest and mapped in figure 6 using eleven different geospatial themes. The interpretations use publicly available geospatial data from the United States of America (USA) National Aeronautics and Space and Administration (NASA) and Japan’s National Space Development Agency (NSDA). Each impact basin has at least three rings with the second largest (Mare Imbrium) having six, and the largest (South Pole - Aitken Basins) having two sets of rings and ITFF strains that span a global hemisphere (fig. 6). Astrobleme structural analysis relied upon the detailed topographic, gravity, and seismic-velocity themes to characterize ITFF strains and obtain model dimensions for the Moon, Earth, and Mars. The largest lunar astroblemes contain the curvilinear mountains chains surrounding impact basins as core components of defined ITFF strain envelopes that cover between 0.5% to over 43% of the globe (fig. 6 and table 1).
The computer methods used to map the astroblemes and conduct a spatial comparison between mapped lithosphere strains and expected seismological responses includes Google Earth Pro (GE Pro), QGIS desktop software (ver. 3.16.14), and the SketchUp (SU) Pro 2020 computer-aided drafting system (CAD). GE Pro and QGIS provide compatible file formats for exchanging data files and exporting the results into SU Pro for 3D modeling of the Moon, Earth, and Mars. The SU Pro extension spirix_textured_sphere by J. Hamilton (ver. 05.29.2016) was downloaded from the Spirix website and used to wrap geographic maps around virtual 3D Earth and Moon globes. Circular histogram analyses were conducted on sets of mapped radial faults within the mapped limits of the largest astroblemes using the QGIS Line Direction Histogram plugin by H. Tveite (ver. 3.1.1, 2020). The Contour QGIS plugin by C. Crook and L. Roubeyrie (ver. 2.0.12, 2023) was used to generate maps of magnetic-field intensity and near-surface crustal, elemental abundances derived from reduced spectroscopy data obtained by NASA’s Lunar Prospector (LP) and website (Feldman and others, accessed 2023). The GE Pro plugin Range Rings for Google Earth by T. Davis and R. Turner (ver. 2023) was used to generate polyline rings of specified radius around impact points lying near the center of large craters. Bolide headings and large faults seen in the various geospatial themes were manually digitized in both GE Pro and QGIS using geographic spatial coordinates. The SU Pro global models uses kilometer distance units.

NASA’s Lunar Reconnaissance Orbiter (LRO) Wide Angle Camera and the Lunar Orbiter Laser Altimeter (LOLA) instrument have enabled the accurate portrayal of the shape of the entire moon at high resolution ( The LRO was launched and began operations in 1997 that continue today. Topographic elevations were surveyed to about one-meter accuracy for each ~118-meter pixel in the global digital terrain model (DTM; Mazarico and others, 2013).

The Gravity Recovery and Interior Laboratory (GRAIL) was another NASA mission run in 2011 and 2012 to obtain high-quality gravitational field mapping of the Moon to help determine its interior structure. The GRAIL mission produced high-resolution maps of the Moon’s gravitational field, including global, free-air and Bouguer gravitational-intensity anomalies (figs. 6C and 6D; Bouguer anomalies are derived from the free-air data by correcting for gravitational effects of variable topography. The GRAIL mission flew twin spacecraft (Ebb and Flow) in tandem around the Moon to map variations in the lunar gravitational field. At the end of the mission, the probes were purposely crashed on the Moon (

A second Bouguer gravity map used in this study is from Watters (2022) that is the basis for mapping very-large fault systems that penetrate the crust into the upper mantle (fig. 6E). This map uses a color scheme that highlights gravity gradients rather than gravity intensities as for the GRAIL themes. The Watter's map seems to emphasize features that have rapid field-intensity changes over small distances like where large crustal fault zones occur that are brecciated, mylonitized, and can locally penetrate to upper-mantle reaches to mediate the ascent of magma (figs. 12, 15, and ). The best examples of this are seen is the eastern margin of the South Pole - Aiken (SPA) Basin astrobleme where braided fault segments stream dark blue through the eastern, lateral reaches to partly bracket this enormous impact basin (fig. 10).  These earliest anomalies are cross cut by younger, high-intensity anomalies that are concentric to impact craters and likely highlight impact-generated igneous dikes that arose from the upper mantle or were generated within the crust by decompression melting.

Global magnetometer data for the Moon were obtained by Japan’s SELENE probe that are available to the public from Japan’s Aerospace Exploration Agency (JAXA) in support of scientific and educational purposes (fig. 6F; Japan’s NSDA SELENE probe was launched in 2007 and orbited the Moon collecting geospatial data until 2009 when it was directed to impact the surface. The magnetometer data were downloaded as tabular data with gridded, 1° data points with the total magnetic field-intensity (F) values measured at 100 km elevation.

Spectroscopic sensing of the Moon’s surface by NASA’s Lunar Prospector (LP) returned major and trace-element abundances in the upper 30 centimeters of ground surface (Feldman and others, accessed 2023). Geospatial variability of elemental concentrations in large impact basins like the Aitken basin and Oceanus Procellarum have been tied to depths of impact excavation and the generation of melt bodies and flood basalts originating from the upper mantle (Hurwitz and Kring, 2014; Uemoto and others, 2017; Zhu and others, 2019). Spectrographic data are free from NASA as gridded ASCII text files formatted with either 1o or 5° geographic cells with center points tagged with either elemental bulk-weight percentage (wt. % ) values or parts-per-million (ppm) concentration units for aluminum (Al), silicon (Si), Iron (Fe), potassium (P), thorium (Th) and uranium (U). Geographic maps of the various elemental abundances were generated for each point theme by contouring the set of values using three to five ranges of values, or quantiles, to colorize the map and thereby allow a geospatial assessment of the elemental abundances for the major impact basins (figs. 6G to 6L). Each geographic map was also added into a GE Pro project as an image overlay further assess spatial comparisons using a virtual globe (figs. 10 and 11). However, it is noted that using data recorded at cell centers leaves small data gaps of either 1° or 5° along the frame of the geographic boundaries. These data gaps are particularly noticeable along longitude -180° when viewed using GE Pro (figs. 6 and 10).

A discussion of the elemental distributions with respect to the larger impact basins is developed below when focusing further on the structural and geophysical aspects of ITFF strains for the six-largest astroblemes (figs. 10 to 14). The locations, sizes and structural aspects for each of the eighteen multi-ring astroblemes therefore relied upon visual inspection of observed surface features gleaned from geophysical anomalies as visualized using geographic maps that are also used as image overlays in the GE Pro virtual globe. Ring spacing noted in table 1 is calculated and compared with the aforementioned √2 factor, and the interpreted headings for the set of bolides are statistically analyzed using a circular histogram that is compared to interpreted bolide headings derived for Mars (fig. 6M; Herman, 2022). The six largest multi-ring impact basins are further analyzed using the NASA and JAXA geospatial data in GE Pro and the mapped dimensions of the basin rings added to a SUP Moon model that incorporates seismological constraints on the manner in which the Moon's interior layering will reflect shock energy (figs. 7). A spatial comparison is then conducted on where reflected shock energy would be focused in concentric alignment around large craters using a CAD Moon model. This is used to highlight outlying regions around large craters where large crustal faults are mapped based on global topographic and gravity maps. Such faults radiate outward from craters with steep dips and in many places correlate spatially with high-intensity gravity anomalies likely stemming from basic, high-density upper-mantle melts (~3.34 gm/cm3 pervading lower-density anorthositic crust (~2.55 - 2.85 gm/cm3; fig. 7).

The astrobleme rings were mapped in hierarchical order and recorded in table 1 with the innermost ring designated 1 and outlying rings noted as 2 through 6. The inner rings either coincide with the crater rim approximated by the first set of topographic fault scarps forming the central depressions, or the limits of gravity mascons for most of the astroblemes (fig. 6 and table 1). Only the SPA basin and the Birkhoff (table 1, no. 9) and Korolev (table 1, no. 16) astroblemes lack central, high-intensity gravity anomalies exceeding 300 mGal, although the latter two have relatively high-intensity gravity anomalies on the order of 100-200 mGal (fig. 6C and 6D). The innermost ring of most basins is mapped along the edge of the central, negative gravity anomaly (fig. 6C). The outer basin rings (2 through 6) are drawn along visible fault scarps or near the limits of concentric, gravitational-intensity anomalies, although fault scarps are not perfectly concentric to craters and form to varying degrees of density and elevations around craters owing to the variance of many impact-related physical factors. For example, there is good evidence that the Mare Orientale impact was at a moderate- to high angle (> 60°) impact from a projectile heading westward owing to having a nearly continuous set of outer rings and cordilleran uplift in a sector downrange of the crater like that seen in missile-test studies (fig. 14). The outer rings of Mare Orientale have a muted topographic expression up range where fault scarps occur and the crust has been stretched resulting in having mare ponded in ringed crustal depressions (fig. 14).

Outer rings correspond with prominent, concentric fault scarps lying outboard of mascons where large tensional fault systems encircle craters and form semi-continuous fault chains that accommodated the rapid, incremental strains accumulated in the target from the absorbed ground energy of impact and subsequent gravitational relaxation. But in other places the mapped rings denote the circumferential limits of thickened crust where radial and concentric faulting spurred the coeval generation of crustal plutons and associated surface volcanism. In these cases, the outer concentric sectors of astroblemes are puffed up where the thickest crust occurs from impact-generated faulting, magmatism and veining. The outermost rings of each astrobleme are mapped to encompass most of the ITFF strains stemming from each impact event with the notable exception of the SPA which has two sets of cratered regions (figs. 6, 10, and 17). The majority of the outer ring correlate with Turtle and others (2005) 'outer limit of deformation' defining the limits of far-field impact strains.

There are also many places on the Moon where sharp, gravity anomalies flare out along linear trends from the the margins of impact basins that lie at the center of large astroblemes. These sharp gravity anomalies stem from deeply penetrating faults that have low-intensity signatures where the crust has been broken with cataclasis and density reduction. On the other hand, high-intensity signatures probably represent faults that have tapped low-titanium (Ti), high-density magma from the upper mantle leading to the local deposition of diabase dikes and mare basalts. For the eighteen ringed basins mapped here, only the SPA Basin doesn't have rings represented in figure 6 because the main impact crater in this vast strewn field lies close to the South Pole with rings paralleling latitude lines that otherwise clutters the maps. A more detailed discussion and representation of impact-generated rings of the SPA is reserved for a later section using GE Pro that provides a clearer representation of the structure than for the geographic maps that spatially inflate and distort polar regions on 2D maps.

Many criteria are used to help interpret the meteorite headings. Primary criteria include down-range crustal excavation together with low-intensity gravity anomalies including the cratered region forming a horseshoe shape with the meteorite heading bisecting the open ends, thereby resembling a trident (Î) with the open end pointing down range. This generally seems to be the case for impacts of low- to moderate obliquity. Those of higher angle display more axial-type of concentric strain fields with closure of the U's open end with continuous uplands and mountain chains. Another strong criteria is having large crustal faults striking in parallel alignment in the central region and sometimes bracketing the crater with sets lying in conjugate arrangement to the axial plane and bisected by the interpreted heading and the horizontal component of the principal, compressive stress axis arising from impact. This phenomenon in rock mechanics is called axial splitting and is one of the dominant, brittle-rupture responses of rocks subjected to uniaxial compression under low confining pressures (Chakraborty and others, 2019). In that respect, it is also common to see radial crustal faults exhibiting a double-shear response giving rise to conjugate fault systems bisected acutely by the meteorite heading as demonstrated for Martian astroblemes and from the aforementioned glass-ball impact experiments (Herman, 2022). Radial faulting arising from axial splitting and conjugate faulting are seen in most of the mapped astroblemes with the most notable exception being the overlapping Maria Imbrium- and Serenitatis, which may have caused vast regions of the crust to be melted and then flooded by Oceanus Procellarum mare (figs. 6 and 11). Another prime criteria is where the free-air and Bouguer gravity maps show mascon axial elongation along the heading line in the free-air theme and horseshoe-shaped anomalies in the Bouguer themes with the open end bisected by the heading. This trend can also parallel far-field magnetic striping within the limits of the astrobleme. The striping consists of alternating, thin bands of varying intensity anomalies situated outside of a cratered region and is best exemplified by the area between Maria Imbrium and Serenitatis where the striping stems from the latter and is reset and gone from inside Mare Imbrium's 490 km concentric ring (figs. 6 and 11) is also exemplified by the gravity expression of the Chicxulub crater on the Yucatan Peninsula of Mexico that was caused by an oblique impact (Gulick and others, 2013). Basin proportionality and structural symmetry was also used to interpret the bolide headings for each astrobleme which is grounded in the observational records of oblique missile impacts like that depicted in figure 14 (bottom), with a basin’s long axis paralleling the missile heading and thickened ground lying down range from structural compounding. Also, astrobleme symmetry, patterns of impact ejecta, and the alignment of multiple craters in a strewn field either arising from projectile fragmentation or bolide spalling provide additional clues that help decipher suspected impact trajectories (Wilhems and others, 1987).

The interpreted bolide headings are therefore constrained by the basins shape, topographic asymmetry, structural, and gravitational expression of the associated fault and fracture systems that commonly display systematic distribution about the impact-trajectory plane (figs. 3 and 4). Oblique strikes occurring at various impact angles produce variable ITFF strain fields including up- and down-range topographic variations and gravity signatures that reflect differential structural processes operating within different blast sectors (Moore, 1976). Missile-test crater studies of oblique projectile strikes have documented broken and tilted material occupying the down range sector whereas the up-range sector has open fracturing and little tilting of the ground. The zone of open fractures differs from the tilted and broken sector in that the original ground surface is often exposed and the original surface is level or displaced downward. Sparse, nearly vertical open fractures in the zone are concentric to the crater edge and confined to the up-trajectory side. Beneath the surface, shattered target material or conjugate fractures form criss-cross patterns that were exposed on the up-trajectory crater wall. The conjugate fractures and tensile fractures perpendicular to them form diamond-shaped blocks with acute angles pointing upward and downward. This fault pattern is seen up range in the Mare Orientale impact basin on the gravity and digital terrain themes (fig. 14). The tendency to have elevated topography down range from structural compounding and crustal thickening corresponds directly with high-intensity gravity anomalies opposing low-intensity, concentric ones situated up range. These relationships are complicated where multiple astrobleme ITFF strains overlap as seen for the five covering much of the near-side of the Moon (fig. 6). Astroblemes therefore commonly display bilateral symmetry with respect to interpreted headings that are also seen on the elemental-abundance maps for the largest impact basins, the SPA and Maria Imbrium-Serenitatis astroblemes and further visualized and discussed below with respect to the six largest, lunar, multi-rings impact basins (figs. 10 to 14).

The inclination aspect of the bolide trajectories are not included in table 1 because their interpretation is the most difficult to deduce along with impact velocities. Bolide sizes are somewhat constrained by crater dimensions (Turtle and others, 2005) but interpreted headings for some of the smaller astroblemes are less certain than the larger ones owing to the relative lack of manifest, widespread asymmetric, ITFF strains that help constrain them. It has been shown that impact obliquity influences crater morphology (Davis and Collins, 2022) and my glass-ball experiments show the transition from axis- to plane-symmetric strain responses that vary based on high (>60°), moderate (30°-59°) and low <30°) impact angles. Vertical impacts have nearly symmetric, radial strain fields and little sector-based structural variance in the respective blast sectors when compared to oblique impacts. Theoretically, the size and strain expression of a bolide will vary as a sine function of its obliquity with the most grounded strain imparted by vertical impacts and the least from very shallow ones. Bolide obliquity for each event is speculated on further in a section below focused on the structural expression of the six largest, lunar astroblemes mapped using GE Pro.

The mapped limits of Oceanus Procellarum and the Aitken Basin as represented in figure 6 are somewhat arbitrary as they are mostly based on visual scrutiny of the NASA DTM (fig. 6A). The area of Oceanus Procellarum listed in table 1 uses the digitized polygon boundary that loosely follows the 0-meter elevation contour. The respected period ages assigned to the various astroblemes is largely based on the work of Tartèse and others (2019), Morbidelli and others (2012) and Wilhelms and others (1987), and it is important to note that these ages will be modified, perhaps significantly based on more robust sampling of the lunar surface. We are still in the formative stages of understanding the absolute timing of impact events on the Moon owing to the difficulties of directly obtaining outcropping geological samples, particularly on the Moon's far side.

Seismological aspects of reflected shock energy

The plausibility of impact-generated shock energy giving rise to radial and concentric crustal faults, mountains and basins is placed into 2D and 3D perspectives below using maps, cross sections, and a CAD model of the Moon’s internal seismological boundaries deduced from a study of Moonquake and meteorite impacts recorded with the Apollo seismic network (fig. 7). The Apollo Passive Seismic Experiment (PSE) resulted from multiple deployments of a surface-based seismological network between 1969 and 1972 from five Apollo Moon landings, and the resulting transmission of seismological data to Earth until September 1977 (Wiezorik, 2009). Weber and others (2011) analyzed the PSE data and reached a consensus on a reference velocity model having eight components including seven concentric layers surrounding a solid inner core. Their velocity model was used to build a 3D geometric model of the Moon with its interior layers and core assembled and rendered using SketchUp Pro 2020 (fig. 7). The layered model includes the crust, two upper mantle layers, three lower mantle layers, and both an outer and inner core. Two, noticeable P-wave velocity inversions occur in the upper and lower mantle where strongly reflected rarefaction waves are returned to the surface from interior material-phase boundaries having reduced acoustic impedance contrasts (430 km and 1224 km radial depths). The spatial limits of the representative impact basins as defined by the concentric fault systems agree very well with the primary shock reflections arising off these two boundaries (figs. 7 and 15 to 18).

Meteorite impacts generate primary shock-compression waves like underground atomic-bomb blasts, but unlike normal earthquakes that stem from the elastic rupture and rebound of subsurface material which generates both P- and S- body waves and surface waves when the radiated energy reaches the ground. Km-scale bolides mostly strike target surfaces at oblique angles and shock compress the target leaving fluidized and plasticized regions around craters where pseudotachylyte melts, mylonite and cataclastic fault zones radiate outward beyond the crater (figs. 2 to 4 and 15). At some point in time and space, widespread plasticity cause by highly pressurized compression waves yields to elastic seismic responses when dissipating shock waves fall below the elastic limit in the medium in which they travel. The transition point from a fluid- plastic state to the elastic state is called the Huguenot elastic limit (HEL) whose extent can vary for the big craters on Earth that are buried and concealed deep beneath sedimentary basins and oceans. Field work around old, large, continental craters have shown that such fluidized, ductile, and brittle shock structures can also include shatter cones mapped at distances of tens to hundreds of kilometers from the crater where they have been raised to the surface and unroofed as with the Precambrian Vredefort (Colliston and Reimold, 1992; Spray, 1998; Allen and others, 2022) and Sudbury (Thomson and Spray, 1996) astroblemes. There is also field evidence in the central Appalachian Mountain region of penetrative, ITFF crustal strains reaching over 700 km distance from the impact crater located at the mouth of Chesapeake Bay and within the compressed, down-range blast sector extending northward through the central Appalachians of Pennsylvania and New Jersey (Mathur and others, Herman, 2022). As such, there is mounting geological evidence of remote ITFF strains occurring on Earth at thousands of kilometers radial distances from large craters, and it becomes a matter of planetary rheology and the seismological behavior of shock waves to place these types of ITFF strain into spatial perspective for the impact basins of The Moon (fig. 7), Mars (fig. 20), and Earth (fig. 22). On Earth, field evidence of ITFF, regional crystal plasticity in quartz, feldspar, and calcite also stem from impact-generated shock waves that instantly raise radial mountain belts and the intervening annular troughs and basins, but traditional thinking places mountain building on Earth, dynamo-thermal metamorphism, and far-field penetrative, secondary structures solely into the realm of gradual tectonic orogenesis which isn’t exclusive given the manner in which km-scale hypervelocity impacts plasticize and strain the crust across vast regions. We see clear evidence from remote sensing of these ITFF strains reaching radial distances of thousands of kilometers around large lunar Impact basins like Mare Imbrium basin crater (figs. 6 and 11). These same processes operate on Earth and Mars, but gradual orogenesis from plate tectonics on Earth and atmospheric weathering on both helps masks their effects.

A shock wave is a strong pressure wave in any elastic medium produced by phenomena that create violent changes in pressure at the wave front. The shock physics of elastic media is well known (Grady, 2017). The shock wave front is an expanding, spherical region of sudden and violent compression and change in stress, density, and temperature. Propagating shock waves cause tectonic disruption that occur above the HEL. Shocked Earth materials can be vaporized, liquefied, plasticized, and undergo solid-solid phase transitions depending upon pressure-intensity variations relative to the shock front and how the energy gets dispersed and absorbed (Bevan, 1994). Shock waves are directed through media in a similar manner as elastic compression waves with respect to radiating energy along wave fronts outward in directions aligned normal to the wave front called ray paths (fig. 9). Wave incidence angles are measured along ray paths from a reference axis aligned normal to a boundary plane, such as an interior compositional or density changes like the phase boundary in the Moon between the upper and lower mantle (~490 km depth; fig. 7). Low incidence angles have steep ray paths relative to the surface and high-incidence angles are oriented at low angles to the boundary.  Dienes and Fisher (1961) determined from studying atomic bomb blasts and numerical modeling that shock energy introduced into a solid medium is both transmitted and reflected at solid-solid interfaces having measurable contrasts in material density and wave-transmission speeds that determine a layers acoustic impedance. This is also generally the case for acoustic, or elastic seismic waves (figs. 8 and 9; Telford and others, 1976). But shock waves differ from elastodynamic waves as they travel faster than sound, and their speed increases as the amplitude is raised (Dienes and Fisher, 1961). But the intensity of a shock wave also decreases faster than does that of an elastic wave, because some of the energy of the shock wave is expended to heat and fracture the medium in which it travels.

When a compressional wave moves through a solid body and encounters an interface with a medium of different acoustic impedance at angles other than normal, the wave energy splits between transmitted energy that continues into the “target” medium along a different ray path, and a newly reflected wave that carries a fraction of the original energy back into the “parent” medium (fig. 9). Dienes and Fisher (1961) found If the acoustic impedance ratio between adjacent layers is as large as 10, or as small as 1/10, the pressure transmitted through parent layer is generally 64% of the original. This is about the greatest reduction that might be expected with common materials. Therefore, for typical cases where acoustic impedance contrasts increase with depth at layer boundaries, most materials transmit roughly 2/3 of the original compression energy through a boundary with only about 1/3 of it being reflected back into the parent medium. But when the impedance contrasts decrease with depth, a layer boundary returns nearly 100% of the wave energy back into the parent material as a rarefaction (tensional, or ‘pressure-release’) wave (figs. 8, 9, and 15). In other words, when the pressure transmitted through a boundary layer is less than that in the incident wave, the reflected wave relieves pressure as a rarefaction wave that returns back into the parent medium, and when it exceeds that in the incident wave, the reflected wave is a compression wave. Shock waves also get diffracted, transmitted into and partially absorbed along layer boundaries at normal incident angles. But in particular, layer boundaries having high, negative impedance contrasts return the bulk of wave front energy as reflected waves back into the parent material at incidence angles exceeding 30o with maximum reflectance occurring at about 60° (fig. 8; Telford and others, 1976). Dienes and Fisher (1961) also report that strong, rarefaction waves lead to tensile fracturing in brittle material and possible spallation at free surfaces like the ground. It is therefore likely that the ringed cordilleran and basins constituting these large basins rise in part from the dispersion and absorption of shock seismicity radiating outward from and focused below large craters as both refracted, transmitted waves and reflected, rarefaction waves. The SU Pro CAD models of The Moon, Mars, and Earth show that the sizes of impact basins and their ringed-basin architecture are dimensionally similar to where primary reflections arise off layered, internal interfaces with inverted impedance contrasts in targeted bodies at ray-path incident angles between 30° and 60° (figs. 15 to 18).

Six, large, lunar-impact basins mapped using Google Earth Pro

A closer inspection of the radial and concentric structures of six of the largest lunar astroblemes follows using GE Pro. The two largest ones are covered first including the SPA and Maria Imbrium and Serenitatis, followed by Maria Nectaris, Crisium, and Mare Orientale. The Maria Imbrium and Serenetatis astroblemes are mapped and discussed together because they structurally overlap and their geophysical expression is closely linked because of their enormity, successive ages, and close proximities.

The South Pole - Aitken (SPA) Basin

The focused structural analysis begins with the most structurally complex region on the far side of the Moon covered by the SPA. It's considered to be the oldest, largest, and deepest impact basin on the Moon but it hasn't been directly sampled and its absolute age is unknown (Spudis and others, 1994; Potter and others, 2012; Garrick-Bethell and Milković, 2018 among others). Hurwitz and Kring (2014) provide a through treatment of the SPA geology and cover both pre- and post-SPA conditions. The reader is referred to this work for a more through discussion of the geological aspects of this massive feature, and how obtaining an absolute age is crucial for constraining the chronology of our solar system evolution.  The SPA is very old and has an aureole of anorthositic crust that locally has some of the highest crater densities on the Moon (Wu and others, 2022). The age of the SPA is probably about 4.3 to 4.4 Ga (Morbidelli and others, 2012).The SPA has an unique structural and geophysical expression involving two sets of regional gravity anomalies that together constitute a vast strewn field formed by multiple projectiles impacting the southern hemisphere. Based on its structural expression as principally defined using the Watters (2002) gravity map (fig. 6E, 10 and 17), the strain field is slightly larger than than mapped by the SPA limits depicted in figure 6, with ITFF strains likely covering half of the lunar surface and ejecta deposits likely spread over most of the globe early in its history. The largest, 'parent' crater is located close to the south pole with the astrobleme fanning out to the north from there and reaching a surface span of over 4800 km directly downrange along a heading of ~007° (figs. 6 and 10, table 1). The center of primary crater is mapped at latitude, longitude -89.5°, 165.5°, an approximate location because of the amount of subsequent, dense cratering occurring there. A second SPA ring is centered down range to the north at longitude 54.42 and latitude 173.48 that was generated with a 820 km radius to roughly follow the 0-meter land elevation along the rim of the basin as seen on the NASA Blue-Steel DTM (fig. 6A and 10).  This ring radius best fits the circular set of geophysical anomalies situated down range that fall in line with the main crater, and only departs from the mapped limits of the basin on its northern edge where it is elongated beyond the circular limits along the interpreted heading (fig. 10).

Hurwitz and Kring (2014) characterized the SPA basin as a 2400 km long by 2050 km wide impact structure centered at 53°, 191°E. That point (AC1; fig. 10) falls very close to the center of the Aitken basin as defined for the aforementioned, secondary ring with center point AC2 on figure 10. The SPA limits therefore extend beyond the basin rim and encompass over 4800 sq. km. of the surface when accounting for radial and concentric faulting within surrounding regions of the lunar highlands. As such, the two cratered regions and associated ITFF strains cover about 47% of the Moon’s surface (table 1, figs. 6 and 10). Large faults also flare out laterally in its wake from the south pole center to the east and west, and other sets of large radial crustal faults flare out from the basin into the highlands along its heading down range (figs. 6 and 10). The strike of the large faults covered by the astrobleme are in agreement with the experimental results of Herman (2022) that show dominant fault strikes normal to the bolide heading for gently inclined (<30°) impacts (fig. 4). Figure 17 (right side)depicts a 200-km diameter bolide inclined at 45° to the surface in order to give this event perspective and illustrates how a moderately inclined, large projectile will tend to spall and shear the lithosphere because of the globe's curved surface.

The central region of this astrobleme is thought to be a vast impact melt sheet, or LIP that was likely differentiated through time with magmatic fractionation of the mare (Uemoto and others, 2017). Potter and others (2012) have determined that after the basin formed, melt remaining within the transient crater pooled to form an impact melt sheet with a radius of ~200 km and a depth of 50 km. The floor of the Aitken basin is at higher elevations and gravity intensities on its north end where it has likely been structurally compounded down range as a wedged section of crust and upper mantle in a manner similar to that depicted for the Mare Orientale basin and in the schematic profile representations of a lunar astroblemes (figs. 12 and 15). About halfway downrange in the basin the crust transitions from excavated, mantle-type lithologies to contracted and thickened mixed upper mantle and crustal rocks in a manner depicted in figure 15. KREEP terrane is mapped spectroscopically in the foreland and western margin of the Aitken basin near where the antipodes of Mare Imbrium and Serenetatis occur (figs. 6G to 6L and 10). The KREEP terrane has relatively high surface concentration of potassium, iron, uranium and thorium with relative depletion of aluminum and silicon (fig. 6G to 6L). This is only the second place on the lunar surface where there is satellite evidence of KREEP on the lunar surface in addition to Oceanus Procellarum and the associated Maria-Imbrium-Serenetatis-Nectaris astroblemes (figs. 10 and 11). The SPA KREEP may simply arise from excavated, upper mantle ejecta that was deposited down range but it may also signal the subtle uplift of KREEP terrane to the surface after being shoved and compacted by an oblique projectile (fig. 15). If this KREEP expression is solely attributed to ejecta deposition the we should see a more uniform spread of these upper-mantle materials across the foreland down range of the crater. But it's possible that this KREEP occurrence is an expression of secondary, anatectic magmatism generated by crustal compounding and heating of the upper mantle with resulting plutons and mineral veins emplaced along concentric, ITFF tensional structures stemming from reflected shock energy as demonstrated above.  Because this basin appears to be the oldest, deepest, and largest impact basin on the Moon, it has been overprinted by repeated bombardment and younger craters but nevertheless retains it's dominant, oblong structural form. The ovoid shape of the basin is a primary criterion used for constraining the bolide’s heading that doesn’t quite align with basin's long axis, but is skewed a little to the west because the basin's shape has been subsequently modified by the younger, overlapping Apollo and Schröedinger multi-ringed basins, and perhaps from impact-antipodal, faulting, igneous flaring and epierogenic welting from the antipodal Maria Imbrium, Serenitatis, and Crisium impact events (Figs. 6 and 7A). Antipodal cracking, heating, magmatism and welting from a series of younger, overlapping, basin-forming events occurring on the opposite side of the globe may also help account for the anomalous KREEP expression here because the SELENE magnetic theme also shows close spatial agreement between high-intensity magnetic anomalies and the aforementioned MISC antipodes (figs. 6F and 10).

This basin likely therefore formed as a strewn field from large, low-angle impacts that was modeled by Schultz and Crawford (2011) as a 170-km diameter bolide impacting at a gentle trajectory with impactor decapitation prevalent. But the impact parameters resulting in this complex, double-ringed basin are speculative with the decapitation scenario likely as the Bouguer gravity expression of the Aitken basin shows numerous, teardrop-shaped craters resulting from spalled fragments that splashed down along a south-to-north heading and leading to secondary basin development (fig. 17). Bolide fragmentation before or after atmospheric entry is also possible that would have resulted in a few main projectiles and slews of smaller ones impacting the south-polar region. The distribution of the anorthositic lunar highlands relative to the SPA appears to be systematic, as if this event could have generated a expansive, associated phase of crustal melting and mineral fractionation leading to the formation or modification of the main lunar highlands. Because it hasn't been directly sampled yet, its possible that this main event, so early in the lunar chronology, formed the primary division between the excavated and melted basin area and the surrounding upland regions around 4.3 to 4.4 Ga (fig. 5).

The gravity expression of the lunar highlands outside of the SPA limits is different from that inside it. Anorthosite inside the SPA limits have higher-intensities than those outside, indicating that the SPA event not only melted and excavated the central cratered region of the astrobleme but also strained a great expanse of the surrounding lunar crust where the relative increase in gravity intensities likely reflect the infusion of iron-rich fractionated melts and secondary mineral veins throughout the anorthositic aureole surrounding the Aitken basin (fig. 6C and 10). Mixing of the primitive crust and upper mantle occurred in the astrobleme core but the diffusion of iron-laden fluids along faults flaring out and surrounding the core structure helps explain the genesis and distribution of pure (PAN) versus siderophilic (FAN) anorthosite as determined from remote spectroscopy and direct sampling (Nagaoka and others, 2023). Higher-intensity gravity signatures of the highlands inside the mapped SPA limits in comparison to lower-intensity ones outside of the SPA limits may represent anorthosite crust that has been magmatically intruded and mineralized with ferrous veins that pervaded this swath of the highlands on the far side within the defined ITFF reaches of the SPA astrobleme. So the overall higher-intensity gravity expression of the anorthositic aureole surrounding the Aitken basin could either have originated by primary fractionation of melted and mixed upper mantle and crustal protoliths by the heat and friction of impact, or they may have originated during secondary impact tectogenesis from anatectic crustal melting and intrusive mixing of basic material from the upper mantle resulting in ferrous veining and magmatism that metamorphosed primary PAN into FAN.

Maria Imbrium and Serenitatis

Astroblemes Maria Imbrium and Serenitatis combine to form most of the second largest region of crustal disruption on the lunar surface stemming from impact tectogenesis. They are ranked second and fourth in size with respect to all of the multi-ring structures (table 1) and major impact events separated slightly in time that are parts of a vast, overlapping strewn field involving other large impact basins including Maria Nectaris and Crisium, together covering most of the Moon's near side, and likely causing the Moon to be tidally locked into Earth so that we perpetually see the 'near' side (fig. 19). As currently interpreted, the relative ages of these four, near-side, large astroblemes is from oldest to youngest: 1) Nectaris, 2) Serenetatis, 3) Crisium, and 4) Imbrium, although this is speculative until absolute ages are obtained. Maria Nectaris and Imbrium are used to mark primary divisions of time in the Moon's history with the former discussed below in the following section.

There is ample stratigraphic and structural evidence of Mare Imbrium being younger than Mare Serenetatis (Wilhems and others, 1986 among others) but they're modeled and discussed together here as a conjoined astrobleme that largely coincides with the surface expression of Oceanus Procellarum (figs. 6 and 11). They're complimentary, large lunar structures that melted, plasticized, and brecciated vast regions of Oceanus Procellarum in close succession. Mare Imbrium is thought to have occurred during the heavy bombardment phase of planetary evolution at around 3.92 ± 12 Ga based on U-Pb ages of impact-melt breccia, phosphates, and zircon grains from more than 20 different samples, five Apollo landing sites, and one meteorite sample (Nemchin and others, 2021; Zhang and others). The age of Mare Serenetatis is thought to be slightly older at about 3.98 Ga (Cadogan and Turrner, 1975). The Imbrium impact was numerically modeled by Zhu and others (2019) as a Moon-shattering event that excavated deep into the mantle with fracturing and spalling of the core. They used model projectiles in the 400 km to 1,000 km diameter range and impact velocities ranging between 3 and 17 km/s.

The successive punches from these large impacts occurring closely in time and space has resulted in ITFF strains occurring over a vast region with a profound structural and geophysical expression on the lunar surface. The outboard gravity expression of the Mare Imbrium astrobleme is enormous, covering about one quarter of the globe (figs. 6 and and table 1). The outer limits of crustal disruption is defined by a set of semi-continuous, sharp, high-intensity gravity anomalies that link up to surround the crater at about 1800 km radial distance from its center point, thereby giving this astrobleme a mascon diameter of 600 km and its overall structural expression exceeding 3600-km diameter. These sharp perimeter anomalies are crustal fault zones developed along the margin of the impact basin with increased material densities likely reflecting magmatic intrusion along deeply penetrating fault systems that likely tap melts generated in the upper mantle as depicted in figures 9 and 15. The strike of the basin-bounding faults veer away from concentricity where they formed in areas having inherited crustal and upper-mantle heterogeneities stemming from preceding large impacts like Maria Serenitatis and Nectaris.

The interpreted headings for Maria Imbrium and Serenetatis lie at high angles to one another with the former located immediately down range of the latter. Much of the compressed and foreland ITTF sector of Serenetatis has therefore been excavated, mixed up and strewn about the Imbrium basin.  The depth of excavation for Mare Serenetatis appears to be mostly confined to the crust as it generally lacks an upper-mantle KREEP expression. The GRAIL and Watters Bouguer gravity themes also show that the Mare Serenetatis mascon appears elongated to the northwest because is superimposed upon at least two earlier, large impacts, with the largest one having been half eroded by the younger Serenetatis. The earlier meteorite impact had a more northerly heading based on the grain seen in the Watters theme (fig. 11). This previously uncharacterized structure is tentatively referred to as the Hunterdon (HU) astrobleme on figure 11 that's now incorporated into the Mare Serenetatis astrobleme. A smaller impact crater occurs immediately to the north of HU and further stretches the overall geophysical expression of the Mare Serenetatis astrobleme out to the north.

The Mare Imbrium structure includes many other sets of gravity 'hot spots' besides those distributed along the perimeter faults that are clustered down range of the mascon and along the structural intersection with Mare Serenetatis. Two of the most prominent sets of linear gravity and topographic anomalies align with Montes Appeninus and Caucasus in concentric arrangement around Mare Imbrium's center point at radii between ~700- to 800-km (fig. 11). These mountain ranges are bisected along the Serenetatis heading and flare out laterally from there which demonstrates how shock energy from the Imbrium event became focused there when running into older, inherited ITFF structures. Other spotty, high-intensity gravity anomalies are concentrated immediately down range along the heading along the heading down range between radial distances of 300 to over 1800 km distance (figs. 6 and 11). This sets of radial anomalies likely reflects axial splitting focused downrange of an oblique strike along a heading of about 174o. It is interesting to note that the SELENE magnetic theme shows that magnetic banding occurs along this same trend with the central spine of the structure running ~N-S and lacking a magnetic signature, whereas the lateral margins of the spine show weak magnetic striping paralleling the central structure (fig. 6F and 11). This could represent the mobilization and expelling of Fe-rich fluids and material from the core from pressure and heat or perhaps, marginal melt bodies accumulating along the margins of the shocked core region. Such melting could happen in either or both the upper mantle and crust. But the composite set of gravity flares occurring down range indicates the likelihood of anatectic magmatism in addition to melt emplacement originating from the upper mantle from crustal compounding, thickening, and heating within a foreland, down-range structural wedge formed by refracted shock energy. It is interesting to note that the spectroscopic signature of the down-range blast sector where the excavated ejecta is focused takes on a triangular form with a base aligned with the up-range chain of large faults and its top pointing directly down range. This form suggests that the KREEP expression of Mare Imbrium is not solely a result of thick ejecta blankets that happen to align with basin-bounding, magmatically active fault systems but also movements of tectonic blocks. The form of the basin boundary line is also asymmetrically extended down range in comparison to up range where the basin limits are nearly straight with a rectangular shape up-range but is more tapered down range. 

Mare Nectaris

Mare Nectaris is the third largest multi-ring lunar astrobleme and marks the beginning of the Nectarian period of lunar geological history and span of heavy bombardment as proposed (fig. 5). The astrobleme is located in the southern hemisphere and resulted from a moderately inclined hypervelocity impact heading northwest that creased the lunar surface and thickened lateral sectors of the strewn field with large ejecta block and an ejecta blanket followed by mantle-derived magmatism emplaced along deeply radial faults as inferred from the GRAIL high-intensity, Bouguer-gravity anomalies that cluster along systematic, northwest-striking surface faults. The crust and upper mantle are split along it's axis with large faults that have focused, high-intensity gravity anomalies and therefore are likely intruded by magma. Mare Nectaris itself overlaps an earlier large crater having a more northerly heading as indicated by the Watters gravity theme. The age of Mare Nectaris was determined using cratering-flux estimates based on its ejecta blanket named the Jansenn Formation; a key, lunar stratigraphic unit. As proposed, the period marks the beginning of a heavy, early, lunar impact flux that declined exponentially with a short half-life (Stuart-Alexander and Wilhelms, 1975) although other impact-flux theories favor a steadier and more constant post-mare flux based on crater counts constrained by radiometric dates (Hartmann, 1970, 1972; Soderblom and Boyce, 1972). 

The magnetic-intensity field theme shows that Mare Nectaris retains a strong magnetic signature that's roughly concentric to the crater but segmented and distorted by the aforementioned superimposed structures. The Mare Nectaris astrobleme is a good example of how impact-tectonic thickening of the crust occurs concentric to a large crater. The outer rings of this astrobleme cannot solely be explained as ejecta blankets as they have sharp, concentric, mountainous ridges spaced at ~440 and 850 km radii that correspond with pronounced gravity and magnetic anomalies indicating that this early, massive structure has deep roots with abundant ITFF igneous plutonism that was subsequently overprinted by the younger trio of large astroblemes including Maria Serenetatis, Crisium, and Smythii (fig. 6F).  Age dating of material within the outer rings and within a lateral sector return three groups of ages including ones from anorthosite associated with Mare Crisium (~3.9 Ga), and older one lateral margins of Mare Nectaris appear to have been melted during formation of the younger Mare Crisium astrobleme.

Mare Crisium

The mare Crisium basin is ranked fifth in size of the eighteen mapped astroblemes with an outer ring reaching 957 km radial distance and covering about 7% of the Moon’s surface area. It is a multi-ring structure formed by a moderately-inclined impact heading east. The astrobleme morphology belies the meteorite's heading along a 079o from the basin center where the innermost ring is missing and an extended mare tract occurs in its place. The Bouguer gravity themes show a set of deep, radial conjugate faults that bracket the mascon, with the most noticeable set flaring out westward and up range (fig. 11). The circular histogram plot of large crustal faults shows a poor correlation with definitive axial splitting because of the scattered histogram plot of large faults within it's limits owing to the overlapping strains from the Maria Nectaris and Smythii astroblemes (fig.6 and 11).

The Soviet Luna 16, 20, and 24 robotic Moon missions were completed within the Mare Crisium astrobleme by drilling into regolith at the various sites and obtaining a mixture of basalts, metaclastic, and anorthositic rocks within 2-m long drill cores that have yielded some very interesting interpretations (Cadogan and Turner, 1977; Meyer, 2009). Among them are an age for the mare basalt in Mare Fecunditatis (Luna 16) of ~3.4—3.5 Ga (fig. 13), a Luna 20 metaclastic fragment dated at ~4.05 and 3.85 Ga that supports widespread cataclysmic bombardment of the moon at that time, and the presence of at least two isotopically distinct, non-radiogenic argon components in the Luna 20 anorthositic sample leading to model plateau ages of ~4.40 Ga to ~4.30 Ga that support SPA as having giving rise to large swaths of the Lunar highlands. But perhaps the most interesting aspect of the LUNA 24 samples is the relatively young age date of 3.3 Ga returned for the mascon mare. The magnetic-intensity theme shows that Mare Fecunditatis is physically connected to Mare Crisium rather than Mare Nectaris (fig. 12) and so the obtained age for outlying melts (3.4 - 3.5 Ga) is just slightly older than the mare within the cratered realm ~3.3 Ga (Meyer, 2009). Because Mare Crisium is assumed to have occurred during the hypothetical late, heavy bombardment (LHB) stage of the lunar chronology, the results of Luna 24 are dismissed as being younger than the age of the astrobleme, and presumed to stem from a younger impact. But if we relax the preconceived notion that Mare Crisium occurred during the LHB stage, then the younger age of this structure is indicated by the close ages Mare Fecunditatis and the crater mare (~3.3 Ga). It's not a far stretch to think that that volcanism within the cratered realm may have occurred over a protected time interval that terminated after outlying effects. This possibility would make the Mare Crisium astrobleme of Late Imbrium age rather than Nectarian age (fig. 5 and table 1).

Mare Orientale

The Mare Orientale astrobleme ranks sixth in size for all multi-ring, lunar structures and is one of the most apparent impact basin on the Moon's far side (figs. 5 and 9). It covers about 4% of the lunar surface (table 1) and has a spectacular multi-ring architecture with a ‘bull’s eye’ first reported by Hartmann and Kuiper (1962). Its location amidst the Lunar Highlands makes its structural expression clear on topographic, gravity, and photogrammetric maps. It’s also situated midway between two very large impact basins amid the lunar highlands with the Aiken basin to the south and Maria Imbrium to the north. The pupil of Mare Orientale’s eye is a dark circular Mare about 278 km diameter corresponding to the mascon where thick layers of impact-generated melts and/or basalt ponded (figs, 6, 13, and 15). The crater is surrounded by at least three concentric mountain ranges bounded inward by normal-fault scarps have elevated footwall blocks nearly forming continuous rings around the crater. The outer two rings reach between 460 to 580 km radial distances and bracket splotchy, high-intensity gravity anomalies that encircle the crater (figs. 15A). This pronounced outer-crustal arch of Mare Orientale is named the Cordilleran Ring (ref) and is topographically elevated over 2 km higher in the down-range sector than for the opposing, up-range one. This likely happened as a result of down-range reverse-shear faulting that compounded and thickened crust like that seen in missile-test craters formed by oblique impacts (fig. 14). The inner low-intensity gravity anomaly is asymmetric with a wider expression down range in comparison to the width up range.

Forward mechanical modeling of the Mare Orientale basin rings by Nahm and others (2013) showed that the largest, outer ‘Cordilleran’ ring is bounded by large-scale normal faults with displacements of 0.8 to 5.2 km, fault dip angles of 54° to 80°, and vertical depth of faulting around 30 km. These faults and the distribution of mare inside the basin suggest that the transient crater had a diameter between 500 and 550 km. They don’t think that the difference in crustal thickness between the western and eastern sides of the basin is a result of the basin-forming event, although the variable topographic expression of the astroblemes agrees with crustal compounding and thickening focused down range like that observed in missile-test craters (fig. 16). There is good geospatial evidence of tectonic inheritance also, with the older and larger Aiken and Maria Imbrium-Serenitatis astroblemes having influenced the locations and forms of subsequent structures where the IFFF strains overlap and interfere with one another (figs. 5 – 10).

The concentric fault systems and mountainous, curved fault scarps have isostatically rebounded, rifted footwalls that reach over 5 km (or ~17,000 feet) above the central mare that likely resulted from the strain effects stemming from reflected shock waves from the acoustic discontinuity separating the upper and lower mantle (um2/lm1; fig. 7). As illustrated in figures 8 and 9, reflected shock waves return to the surface with about 60% of their original energy, but as pressure-release (rarefaction) waves that induce regional, concentric tensional, ITFF failure around the crater. These concentric faults are clearly accompanied by magmatic intrusions in the form of lava flows, ring dikes (Andrews-Hanna and others,2018) and plutons that pervade the shallow mantle and crust along both radial and concentric faults that mediated the ascent of mantle-derived magma (fig. 11B). It thus appears that rapid, shock reflections from the mantle spurred the development of vast, deeply penetrating crustal rifts that span thousands of kilometers length. The splotchy, high-intensity gravity anomalies of the Cordilleran ring probably signal the occurrence of dense, basic, crustal plutons that may have locally fractionated into more acidic intrusive complexes and volcanoes over time. Another possibility is that crustal anatexis has occurred in compounded and thickened highlands crust occurring down range of craters in most astroblemes. Differentiated, evolved, acidic magmas have been obtained from direct Lunar sampling, and the periodic magmatic genesis within down-range overlapping strain fields can help explain the various ages obtained (ref.). The structural expression of these combined processes is to puff up the outer collar of an astrobleme like that clearly seen in Mare Orientale.

The circular histogram plot of faults occurring within the basin (fig. 12A) have fault-strike maximums that do not parallel the interpreted heading and that likely reflect the inheritance of pre-existing faults in the region imparted by the larger, bracketing Aiken and Maria Imbrium-Serenitatis impacts.  It therefore is possible that complex structural movements have occurred on the older faults caused by tectonic overprinting, and the likelihood of having older faults involved in younger magmatic activity. The primary criteria used for interpreting the Mare Orientale heading is the topographic expression of the basin with the heading pointing to the highest, down-range cordilleran and the cross section paralleling that trend (fig. 12). Another criterion arose from the subtle topographic ridges within the central mare as seen in the digital elevation models that are oriented at high-angles to the interpreted heading and that likely stem from post-mare isostatic, structural adjustments causing subtle fault scarps to develop above blind faults within the limits of the crater (fig. 15).

Mars and Earth Seismological Models

The same methods used to model the seismic responses to large impacts on the Moon are also applied to Mars (fig. 21) and Earth (fig. 23) using global seismic-velocity profiles together with 3D CAD models to derive ITFF strain solutions for impact-shock reflections. Mars and Earth are similar insofar as the only major, interior, inverted acoustic-phase boundary occurs at the liquid outer cores beneath overlying plastic mantles. Figures 21 and 22 show the interior layering of Mars shaving strong shock reflections off the liquid outer core in relationships to the Syria-Sinai-Solis Planums astrobleme in Mars. The model shows a direct spatial correlation between major concentric, crustal structures and the dimensions of strongly reflected shock rarefactions. Figure 23 and 24 show similar relationships for Earth where strong reflections rising back to the surface off the outer core spatially correlate with a 5000-km radius rings around the large, suspected Congo impact basin on Earth, and how that event may be responsible for spearheading the breakup of Pangaea and emplacement of the 200 Ma central Atlantic magmatic province (CAMP) that I have had the pleasure to map in parts of New Jersey and New York.


There is a large body of literature concerning the Moon’s genesis and geological evolution as it plays a pivotal role in our understanding of our place in our Universe. Recent numerical thermal and geodynamic models of the Moon and large impacts resulting in the multi-ring basins have been done in three dimensions including 2D geometry and time (Wieczorek and Phillips, 2000, Zhu and others, 2019). What is gleaned from this work, among many others, is that the Moon’s crust varies in thickness from about 30 to 65 km in thickness with respect to the Maria and Highlands terrains, and with respect to the two largest astroblemes, the SPA and Maria Imbrium-Serenitatis astroblemes respectively. These three bolide-impact events imprinted and significantly altered the expression of a primitive, lunar magma ocean (LMO) that is thought to have fractionated into the lowland Mare and anorthositic Highlands. As seen illustrated above, large regions of the Moon have been repeatedly melted, fractionated, mixed up and tossed about from cosmic bombardment and planetary accretion. Visual inspection of the geospatial data show that the SPA carved out a vast section of the southern, polar region and is collared by stretches of highlands that reach the maximum lunar altitudes far down range where focused, refracted shock energy structurally thickened and elevated the upper mantle and crust. It also appear that the largest impact craters are concentrated in the southern hemisphere in comparison to the north which is also the case for Mars and Earth. But most of the Lunar KREEP terrane is focused within the mid-latitude Mare Imbrium astrobleme, and to a lesser extent the SPA. Only the largest four multi-ring astroblemes show impact excavation to upper-mantle levels (figs. 6, 10 and 11).
This study has outlined aspects of the 18 largest, lunar, multi-ring astroblemes and provided a secondary glance at five of the largest ones as a preliminary investigation into their structural nature that appears to hinge on how the global interior is structured. Other geophysical aspects and structural details surrounding the 12 smaller astroblemes await further scrutiny but will undoubtedly shed more light on the nature of ITFF scaling for larger versus smaller astroblemes. But what we really need from the Moon are absolute ages for specific geological structures based on outcropping rock samples rather than grab samples of loose surface materials and regolith that can have ejecta origins located hundreds to thousands kilometers distance from collection points. In this respect the Luna core samples of basalt-laden regolith are amazing achievements but subject to the widespread deposition of impact ejecta across lunar hemispheres, and then reworked into regolith by successive cratering and ejecta depositional events. The vastness of Oceanus Procellarum, comprising over 10% of the Moon’s surface area (table 1 and fig. 6) testifies to the extreme distances impact-spurred volcanic basalts can flow across the surface to infill crustal depressions and mask the visual identification of craters predating the emplacement of the volcanic flows and melt sheets.

The magnetic-field data show a north-south striking grain to the east of the Maria Imbrium, Serenitatis, and Nectaris astroblemes that may result from mineral-fractionation processes and compositional banding in the partially melted deep mantle from iron segregating outward from the compressed spine of the Imbrium impact as previously mentioned. It's herein noted that the most intense magnetic-field anomalies occur in the northwest rims of the SPA near the antipodes for the massive Maria Imbrium, Serenitatis, and Crisium multi-ring basins. This spatial correlation emphasizes the relative importance of antipodal ITFF strains in the upper-mantle and crustal from cracking and decompression melting appear significant only for the largest astroblemes.

Wieczorek and Phillips (2000) have shown how the lunar Moho is the top of the KREEP upper-mantle layer that has been differentially uplifted by tens of kilometers beneath young multi-ring basins. This behavior has commonly been attributed to the vast quantity of material that is excavated during the impact event and the subsequent rebound of the crater floor. Wieczorek and Phillips (1999) used this observation to argue that most of the lunar basins formed in accordance with the premise of proportional scaling. Specifically, they found that the depth/diameter ratio of the excavation cavity for most of the young basins was equal to about 0.1 independent of crater size. This work offers a complimentary explanation for the the differential occurrence of KREEP terrane occurring principally downrange of large craters coring asymmetric astroblemes and with large-basin antipodal welting. My intent in conducting this research was to spatially examine the geometric links between radiated impact-shock energy and the resulting ITFF radial and concentric crustal faulting. In that regard I am satisfied with the derived geometric association with interior seismogenic layering and crustal strain fields stemming from impact tectogenesis. But the correlation of strong rarefaction shock waves pulling the crust apart from beneath minutes after a meteorite collision were an unexpected aspect stemming from this work that helps explain rift tectonics on Earth.

This work compliments recent advances in impact tectonic theory by Buthman (2022) and Herman (2022) that show how, where, and when sudden and catastrophic tectonic episodes of mountain and basin formation have occurred on Earth and Mars from periodic bombardment by km-scale bolides striking at hypervelocity speeds. Impact-generated tectonic events suddenly punctuate geological time on Earth that otherwise reflects the slow, steady, and comparatively uniform tectonic processes operating near the planetary surface most of the time such as the slow-spreading oceanic ridges, subducting tectonic plates, and stratigraphic accumulation arising from ordinary tectonic orogenesis. But large, catastrophic impact events also correlate temporally with rapid and brief biological mass extinctions on Earth and regional magmatic events that help us partition geological time into the various Eras, Periods, and Epochs (Herman, 2022). Plutonism and volcanism are constructive geological processes that can topographically elevate and sometimes thicken the crust where large igneous provinces (LIPS) form beneath oceanic-spreading ridges, as oceanic seamounts, or topographic highlands and mountains of terrestrial bodies. It is shown herein that impact tectogenesis of the Moon stems from absorbed ground energy imparted by hypervelocity, km-scale meteorites, and the manner in which shock energy is absorbed can be partitioned into refracted and reflected shock strain mechanisms that account for what we can sense using satellite imagery. These concepts also apply to other terrestrial bodies like the mapped ITFF structures on Earth. The pronounced vertical tectonic shifts that have been noted since the advent of geology as a science can also stem from the extraterrestrial, impact-tectonic agents of bolide bombardment and accretion that are integral agents of solar system evolution.

It has been nearly one year since I began analyzing lunar structures in the hopes of gaining a better understanding of how ITFF welting happens on Earth. From this I have realized how fascinating the Moon is, have developed new vocabulary, and an alternative explanation for how ITFF ring structures on the Moon principally arise from primary shock reflections returning to the surface off interior layer boundaries having inverted, subjacent acoustic impedances. These hypotheses are only made possible through the gathering and sharing of global geophysical data by multi-national agencies. So even thought humanity struggles to coexist in harmony, this work proves that we effectively cooperate as a scientific community globally to advance our understanding of our natural surroundings. I hope that these contributions to lunar geology prove useful.


Allen, N. H., Nakajima, M., Wünnemann,K., Helhoski, S., and Trail, D., 2022, A revision of the formation conditions of the Vredefort crater: Journal of Geophysical Research: Planets, v. 127, 15 p., DOI 10.1029/2022JE007186

Andrews-Hanna J.C., Head J.W., Johnson B., Keane J.T., Kiefer W.S., McGovern P.J., Neumann G.A., Wieczorek M.A., Zuber M.T., 2018, Ring faults and ring dikes around the Orientale basin on the Moon: Icarus. v. 310, p. 1-20, DOI 10.1016/j.icarus.2017.12.012

Boehnke P. and Harrison, T. M, 2016, Illusory Late Heavy Bombardments: Proceedings of the National Academy of Sciences, v. 113, no. 39,

Cadogan P. H. and Turner G. , 1977, 40Ar—39Ar Dating of Luna 16 and Luna 20 samples: Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences, v. 284, Iss. 1319, DOI 10.1098/rsta.1977.0007

Chakraborty, S., Bisai, R., Palaniappan, S. K., and Pal, S. K., 2019, Failure modes of rocks under uniaxial compression tests: An experimental approach: Journal of Advances in Geotechnical Engineering, v. 2., issue 3., DOI 10.5281/zenodo.3461773

Cocco, M., Aretusini, S., Nielsen, S. B., Spagnuolo, E., Tinit, E., and Di Toro, G., 2023, Fracture energy and breakdown work during earthquakes: Annual Review Earth and Planetary Sciences. V. 51, p. 217–252

Colliston, W. P. and Reimold, W. U. 1992, Structural review of the Vredefort dome: Lunar and Planetary Inst., International Conference on Large Meteorite Impacts and Planetary Evolution,

Davison, T. M., & Collins, G. S., 2022, Complex crater formation by oblique impacts on the Earth and Moon" Geophysical Research Letters, v. 49, 9 pages, DOI 10.1029/2022GL101117

Dienes, J. K. and Fisher, R. H., 1961, Shock transmission through a solid-solid interface: General Dynamics General Atomic Division, Special Nuclear Effects Laboratory, San Diego, CA, 34 p.

Dziewonski, A. M., and D. L. Anderson, 1981, Preliminary reference Earth model: Phys. Earth Plan. Int. v. 25, p. 297-356.

Fassett, C. I., J. W. Head, S. J. Kadish, E. Mazarico, G. A. Neumann, D. E. Smith, and M. T. Zuber, 2012, Lunar impact basins: Stratigraphy, sequence and ages from superposed impact crater populations measured from Lunar Orbiter Laser Altimeter (LOLA) data, Journal of Geophysical Research, v. 117, E00H06, DOI 10.1029/2011JE003951

Feldman, W. C., Prettyman, T. H., Belian, R. D., Elphic, R. C., Gasnault, O., Lawrence, D. J., Lawson, S. L., . Moore, K. R., Binder, A. B., and Maurice, S., Accessed 2023, Lunar prospector reduced spectrometer data - Special products: National Aeronautics and Space Administration:

French, B. M., 2004, The importance of being cratered: The new role of meteorite impact as a normal geologic process: Meteoritics & Planetary Science v. 39., no. 2., p. 167-197

Garrick-Bethell, I. and Miljković, K., 2018, Age of the lunar south pole-Aitken Basin: 49th Lunar and Planetary Science Conference 2018 (LPI Contribution No. 2083),

Genova, A, Goossens, S., Lemoine, F. G., Mazarico, E, Neumann, G. A.; Smith, D. E.; Zuber, M. T., 2016, Seasonal and static gravity field of Mars from MGS, Mars Odyssey and MRO radio science: Icarus, v.272, p. 228–245. DOI 10.1016/j.icarus.2016.02.050

Gomes, R., Levinson, H. F., Tsiganis, K., and Mobidelli, A., 2005, Origin of the cataclysmic Late Heavy Bombardment period of the terrestrial planets: Nature, v. 435, p. 466 - 469, DOI 10.1038/nature03676

Grady, D., 2017, Physics of Shock and Impact: Volume 1, Fundamentals and dynamic failure: IOP Publishing Lts., 103 p., DOI 10.1088/978-0-7503-1254-7ch1

Gulick, S.P.S., Christeson, G.L., Barton, P.J., Grieve, R.A.F., Morgan, J.V., and Urrutia-Fucugauchi, J., 2013, Geophysical characterization of the Chicxulub impact crater: Review of Geophysics, v. 51, iss. 1, p. 31-52. DOI 10.1002/rog.20007,

Hackman, R. J., 1963, Stratigraphy and structure of the Montes Apenninus quadrangle of the Moon: U.S. Geological Survey Lunar and Planetary Investigations, Part A. No. 1, 8 p.

Harrison, T. M., Hodges, K. V. , Boehnke P., Mercer, C. M., and Parisi, A., 2018, Problematic evidence of a late heavy bombardment: Bombardment: Shaping Planetary Surfaces and Their Environments, LPI Contribution No. 2017, 2013.pdf,

Hartmann, W. K., 1970, Lunar cratering chronology: Icarus, vol. 13, no. 2, p. 299-301.

Hartmann, W. K., 1972, Moons and planets: Tarrytown-on-Hudson, N.Y., Bogden and Quiglen, 404 p.

Hartmann, W. K. and Davis, D. R., 1975, Satellite-sized planetesimals and lunar origin: Icarus v. 24, p. 504-515,

Hartmann, W. K. and Kuiper, G. P., 1962, Concentric structures surrounding lunar basins: Communications Lunar Planetary Lab., v. 1, p. 61-66 and 77 plates.

Hartmann, W. K. and Wood, C., 1971, Moon: Origin and evolution of multi-ring basin: Earth, Moon and Planets, v. 3, no. 1, p. 3 - 78.

Herman, G. C., 2009, Steeply-dipping extension fractures in the Newark basin: Journal of Structural Geology, v. 31, p. 996-1011.

Hurwitz, D. M., and Kring, D. A., 2014, Differentiation of the South Pole–Aitken basin impact melt sheet: Implications for lunar exploration, Journal of geophysical research: Planets, v.119, p. 1110–1133, DOI 10.1002/2013JE004530.

Johnson, B. C., Andrews-Hanna, J. C., Collins, G. S., Freed, A. M., Melosh, H. J., & Zuber, M. T., 2018, Controls on the formation of lunar multiring basins: Journal of Geophysical Research: Planets, v. 123, p. 3035–3050. DOI 10.1029/2018JE005765

Lindsay, J. F., 1976, Lunar Stratigraphy and Sedimentology, in Kopal and Cameron, A.G.W., eds., Developments in Solar System- and Space Science, v. 3: Elsevier, 302 p. ISBN 0-444-414443-6Z

Martin, H., Albarede, F., Claeys, P., Gargaud, M., Marty, B., Morbidelli, A., and Pinti, D., 2006, 4. Building of a hospitable planet: Earth, Moon, and Planets v. 98, p. 97-151, DOI 10.1007/s11038-006-9088-4

Mazarico, E., Rowlands, D. D., Neumann, G. A., Smith, D. E., Torrence, M. H., Lemoine, F. G., & Zuber, M. T., 2012, Orbit determination of the Lunar Reconnaissance Orbiter: Journal of Geodesy, v. 86, no. 3, p, 193-207. DOI 10.1007/s00190-011-0509-4

McKinnon, W. B., and Melosh, H. J., 1980, Evolution of planetary lithospheres: Evidence from multiringed structures on Ganymede and Callisto: Icarus, vol. 44, Iss. 2, p.454–471. DOI 10.1016/0019-1035(80)90037-8

Melosh, H. J. , 1989, Impact Cratering: A Geologic Process, Oxford Univ. Press, Oxford. 245 p

Melosh, H. J., and Ivanov, B. A., 1999, Impact crater collapse: Annual Review Earth Planetary Sciences, v. 27 p. 385–415

Melosh, H. J., and McKinnon, W., B., 1978, The mechanics of ringed basin formation: Journal of Geophysical Research, vol. 5, Iss. 11, p. 897-992

Meyer, C., 2009, Luna 24 Drill core; 170 grams: in Meyer, C., Lunar Sample Compendium: U.S.A. National Aeronatics and Space Administration,

Miljkovic, S., 2018, Moon's crustal thickness: NASA/JPL-Caltech Photojournal:
Monteux, J. and Arkani-Hamed, J., 2019, Shock wave propagation in layered planetary interiors: Revisited: Icarus, v. 331, p. 238-256. DOI 10.1016/j.icarus.2019.05.016

Moore, H. J., 1976, Missile Impact Craters (White Sands Missile Range, New Mexico) and Applications to Lunar Research; Contributions to Astrogeology: U. S. Geological Survey Professional Paper 812-B, 47 p

Morbidelli, A., Marchi, S. , Bottke, W. F. and Kring, D. A., 2012, A sawtooth-like timeline for the first billion year of lunar bombardment, Earth and
Planetary Science Letters, v. 355-356, p. 144–151

Nagaoka, H., Ohtake, M., Karouji, Y., Kayama, M., Ishihara, W., Yamamoto, S., and Sakai R., 2023, Sample studies and SELENE (Kaguya) observations of purest anorthosite (PAN) in the primordial lunar crust for future sample return mission: Icarus, v. 392, 12 p., DOI 10.1016/j.icarus.2022.115370

Nahm, A. L., Öhman, T. and Kring, D. A., 2013, Normal faulting origin for the Cordillera and Outer Rook Rings of Orientale Basin, the Moon, Journal of Geophysical Research. Planets, v. 118, p. 190–205, doi:10.1002/jgre.20045

Nemchin, A. A., Long, T., Jolliff, B. L., Wan, Y., Snape,J. F., Zeigler, R., Grange, M. L., Liu, D., Whitehouse, M. J., Timms, N. E. and Jourdan, F., 2021, Ages of lunar impact breccias: Limits for timing of the Imbrium impact: Geochemistry, v. 81, issue 1, ISSN 0009-2819, DOI: 10.1016/j.chemer.2020.125683,

Irving, J. C. E., Lekic, V., and 32 others, 2023, First observations of core-transiting seismic phases on Mars: Earth, atmospheric, and planetary sciences, v. 120, no. 18, 10 p., DOI 10.1073/pnas.2217090120

Johnson, B. C., Andrews-Hanna, J. C.,Collins, G. S., Freed, A. M., Melosh, H. J., and Zuber, M. T., 2018, Controls on theformation of lunar multiring basins.Journal of Geophysical Research: Planets, v. 123, p. 3035–3050. DOI 10.1029/2018JE005765

Lakce, R. H. and Onat, E. T., 1962, A comparison of experiments and theory in the plastic bending of circular plates, Journal of the Mechanics and Physics of Solids, v. 10, Iss. 4, P. 301-308, ISSN 0022-5096

Lognonné, P., Banerdt, W. B., Giardini, D., and 178 others. 2019, SEIS: Insight’s Seismic Experiment for Internal Structure of Mars: Space Science Reviews, v.  215, no. 12, 170 p., DOI 10.1007/s11214-018-0574-6

Phillips, R. J., Conel, J. E., Abbott, E. A., Sjogren, W. L., & Morton, J. B., 1972, Mascons: Progress toward a unique solution for mass distribution: Journal of Geophysical Research, v. 77, p. 7106–7114. DOI 10.1029/jb077i035p07106

Pike, R. J. and Spudis, P. D, 1987, Basin-ring spacing on the Moon, Mercury, and Mars: Earth Moon and Planets, v. 39, p, 129–194. DOI 10.1007/BF00054060

Potter, R. W. K., 2015, Investigating the onset of multi-ring impact basin formation: Icarus v. 261 p. 91–99, DOI 10.1016/j.icarus.2015.08.009.
Potter, R. W. K., G. S. Collins, W. S. Kiefer, P. J. Mcgovern, and D. A. Kring, 2012, Constraining the size of the South Pole-Aitken basin impact: Icarus, v. 220, no. 2, p. 730–743, DOI 10.1016/j.icarus.2012.05.032

Ringwood, A. E. and Kesson, S. E., 1977, Composition and origin of the moon: Proceedings Lunar Scientifc Conference, 8th, p. 371-398,

Singer, K. N., Jolliff, B. L., and McKinnon,W. B., 2020, Lunar secondary cratersand estimated ejecta block sizes reveal ascale‐dependent fragmentation trend: Journal of Geophysical Research: Planets, v. 125, e2019JE006313

Spray, J.G., 1998, Pseudotachylyte Type Area: The Vredefort Structure, South Africa: Chapter 22 in Fault-related Rocks; A Photographic Atlas, Snoke, A. W., Yullis, J., and Todd, V. R., eds., Volume 410 in the series,

Spudis, P. D., 1993, The Geology of Multi-Ring Impact Basins: The Moon and Other Planets (Cambridge Planetary Science Old). Cambridge: Cambridge University Press. doi:10.1017/CBO9780511564581

Spudis, P. D., Gillis, J. J., and Reisse, R. A., 1994, Ancient Multiring Basins on the Moon Revealed by Clementine Laser Altimetry: Science, v. 266, p. 1848-1851, DOI 10.1126/science.266.5192.1848

Spudis, P. D. and Sharpton, V. L., 1993, Impact basins on Venus and some interplanetary comparisons: Lunar and Planetary Institute, v. 24, p. 1339-1340,

Spudis, P. D., Martin, D. J. P., and Kramer, G., 2014, Geology and composition of the Orientale Basin impact melt sheet: Jornal of Geophysical Research: Planets, v. 119, p, 19–29, DOI 10.1002/2013JE004521.

Stöffler, D., and Ryder, G., 2001,Stratigraphy and isotope ages of lunar geologic units: Chronological standard for the inner solar system: Space Science Reviews, v. 96, p. 9–54 DOI 10.1023/A:1011937020193

Stuart-Alexander, D., E., and Wilhelms, D. E., 1975, The Nectarian System, a new lunar time-straigrpahic unit: U. S. Geological SUrvey Journal of Research, vol. 3., no.1, p. 53-58. URL:

Tartèse, R., Anand, M., Gattacceca, J., Joy, K. H., Mortimer, J. I., Pernet-Fisher, J. F., Russell, S., Snape, J. F., and Weiss, B. P., 2019, Constraining the Evolutionary History of the Moon and the Inner Solar System: A Case for New Returned Lunar Samples: Space Science Reviews v. 215, no. 54, 50 p., DOI 10.1007/s11214-019-0622-x

Telford, W. M., Geldart, L. P., Sheriff, R. E., and Keys, D. A., 1976, Applied Geophysics: Cambridge University Press, New York, USA, 2004. 860 p.

Thompson, L. and Spray, J. 2004, Pseudotachylyte petrogenesis: constraints from the Sudbury impact structure. Contributions Mineralogy and Petrology v. 125, p. 359–374 (1996). DOI 10.1007/s004100050228

Toksöz, M. N., Dainty, A. M., Solomon,S. C., and Anderson, K. R., 1974, Structure of the Moon: Review of Geophysics, v. 12, no. 4., p. 539-567. DOI 10.1029/RG012i004p00539

Turtle, E.P., Pierazzo, E., Collins, G.S., Osinski, G.R., Melosh, H.J., Morgan, J.V., and Reimold, W.U., 2005, Impact structures: What does crater diameter mean?,in Kenkmann, T., Hörz, F., and Deutsch, A., eds., Large meteorite impacts III: Geological Society of America Special Paper 384, p. 1–24.
Uemoto, K., Ohtake, M., Haruyama, J., Matsunaga, T., Yamamoto, S., Nakamura, R., Yokota, Y., Ishihara, Y., and Iwata, T., 2017, Evidence of impact melt sheet differentiation of the lunar South Pole-Aitken basin: Journal of Geophysical Research; Planets, v. 122, p. 1672–1686, DOI 10.1002/2016JE005209

Wang, Y., Forsytha, D. W., Raua, C. J., Carrieroa, N., Schmandtb, B., Gahertyc, J. B., and Savaged, B., 2013, Fossil slabs attached to unsubducted fragments of the Farallon plate: Earth, atmospheric, and planetary sciences, v. 110, no. 14, p. 5342-5346

Watters, T. R., 2022, Lunar wrinkle ridges and the evolution of the nearside lithosphere: Journal of Geophysical Research: Planets, v. 127, 14 p., DOI 10.1029/2021JE007058

Weber, R. C., Lin, Pei-Ying, Garnero, E. J., Williams, Q., and Lognonné, P., 2011, Seismic Detection of the Lunar Core. DOI 10.1126/science.1199375

Werner, S. C., Bultel, B., Rolf, T., and Fernandes, V. A.,2022 Orientale Ejecta at the Apollo 14 Landing Site Implies a 200-million-year Stratigraphic Time Shift on the Moon: Planetary Science Journal, v. 3, no. 3., 12 p.,; DOI 10.3847/PSJ/ac54a6

Wieczorek, M. A., 2009, The interior structure of the Moon: What does geophysics have to say?: Elements, v. 5, no., p. 35-40

Wieczorek, M.A. and Phillips, R.J., 2000, The “Procellarum KREEP Terrane”: Implications for mare volcanism and lunar evolution: Journal of Geophysical Research, v. 105, no. E-8, p. 20, 417 to 420, and 430.

Wieczorek, M. A., Weiss, B. P., Breuer, D., Cébron. D., Fuller, M., and others, 2022, Lunar magnetism: HAL Open Science document hal-03524536, 44 p.,

Wilhelms, D. E., McCauley, J. F., and Trask, N. J., 1987, The geologic history of the Moon: United States Geological Survey Professional Paper 1348, 302 p. DOI 10.3133/pp1348

Wu, B., Wang, Y., Werner, S. C., Prieur, N. C., & Xiao, Z., 2022, A global analysis of crater depth/diameter ratios on the Moon: Geophysical Research Letters, vol. 49, 14 p., DOI 10.1029/2022GL100886

Yoshida, M., and Hamano, Y., 2015, Pangea breakup and northward drift of the Indian subcontinent reproduced by a numerical model of mantle convection: Nature Scientific Reports, vol. 5., article no. 8407, 8 p., DOI 10.1038/srep08407

Zhang F., Pizzi, A., Ruj, T., Komatsu, G., Yin A, Dang Y, Liu. Y., Zou, Y., 2023, Evidence for structural control of mare volcanism in lunar compressional tectonic settings. Nature Communications, v. 14, article no. 2892, DOI 10.1038/s41467-023-38615-1. PMID: 37210379; PMCID: PMC10199890

Zhang, J.; Head, J.W.; Liu, J.; Potter, R.W.K., 2023, Lunar Procellarum KREEP Terrane (PKT) Stratigraphy and Structure with Depth: Evidence for Significantly Decreased Th Concentrations and Thermal Evolution Consequences. Remote Sens., 15, 1861. DOI 10.3390/rs15071861

Zhu, M.‐H., Wünnemann, K., Potter, R. W. K., Kleine, T., and Morbidelli, A., 2019, Are the Moon's nearside‐farside asymmetries the result of a giant impact?: Journal of Geophysical Research: Planets, 124, 2117–2140. DOI 10.1029/2018JE005826

Introduction * Review * Geographic maps of eighteen lunar astroblemes  * Seismological aspects * The South Pole - Aitken basinMaria Imbrium and Serenetatis * Mare Nectaris * Mare Crisium * Mare Orientale * Mars and Earth modelsDiscussion References * GE Pro Moon KMZ file


IT iconb