Prolonged Rock Exhumation at the Rims of Kilometer‐Scale Lunar Craters

Nypaver, C. A.; Thomson, Bradley J.; Fassett, C. I.; Rivera-Valentín, E. G.; Patterson, G. W.

doi:10.1029/2021je006897

Cited by 13 publications

(19 citation statements)

References 42 publications

(94 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Several of the instruments on the Lunar Reconnaissance Orbiter (LRO) have provided new data relevant to rock populations and regolith evolution, particularly the Lunar Reconnaissance Orbiter Camera (LROC; Robinson et al., 2010), the Diviner Lunar Radiometer Experiment (Hayne et al., 2017; Paige et al., 2010), and Miniature Radio Frequency (Mini‐RF) radar (e.g., Cahill et al., 2014; Nozette et al., 2010; Raney et al., 2011). Many analyses of these data have focused on the rock abundance in craters' ejecta (Ghent et al., 2014; Fassett et al., 2018; Mazrouei et al., 2019; Nypaver et al., 2021), rather than in the intercrater regions of the maria. Additionally, the abundance of meter‐scale rocks has also been manually assessed with LROC in a few selected areas of particular interest, such as landing sites (Li et al., 2017; Watkins et al., 2019; Wu et al., 2018), as well as on a more global basis with machine learning (Bickel et al., 2020).…”

Section: Introductionmentioning

confidence: 99%

Rock Abundance on the Lunar Mare on Surfaces of Different Age: Implications for Regolith Evolution and Thickness

Vanga

Fassett

Thomson

et al. 2022

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

The surface of the Moon is covered by regolith, a layer of poorly sorted particles ranging in size from dust to boulders, the median particle size of which is very fine sand (Carrier et al., 1991). Because of its ubiquity, the regolith is primarily what we observe on the Moon with remote sensing instruments and is the material we interact with when exploring the lunar surface. Many of the important geological, geochemical, mineralogical, and geotechnical characteristics that define lunar regolith were established by the Apollo missions and its precursors (e.g., McKay et al., 1991). Modern remote sensing methods allow us to extrapolate regolith characteristics from landing sites to places that have not yet been explored in situ.The existing paradigm for regolith growth and evolution is that it is dominated by impact cratering and gardening (e.g., Costello et al., 2018;McKay et al., 1991;Shoemaker et al., 1967). Because of the similarity between impacts and explosions, this can be thought of as an explosive demolition process. Using the Neukum production function (NPF) for the Moon combined with scaling calculations to determine the size of impactors (Ivanov, 2001), the kinetic energy delivered by impacts over the last 3 Ga that formed 10 m ≤ D ≤ 500 m craters is ∼3-6 × 10 15 J/ km 2 , approximately equivalent to a megaton of TNT/km 2 , with ∼10 4 unique events/km 2 . This demolition process is why there is almost no bedrock exposed on the Moon's upper surface, the median grain size of the surface has been reduced to very fine sand, and regolith thickens with time.

show abstract

Section: Introductionmentioning

confidence: 99%

Rock Abundance on the Lunar Mare on Surfaces of Different Age: Implications for Regolith Evolution and Thickness

Vanga

Fassett

Thomson

et al. 2022

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

show abstract

“…Such a scenario is predicted for rocky areas, where a range of rock sizes are expected (Bandfield et al 2011;Hayne et al 2017). This is supported by the finding that CPR values remain high in crater ejecta blankets for >3 Ga, which suggests that radardetectable (i.e., >∼10 cm) rocks persist in the near-subsurface even if the surface appears relatively rock-free in Diviner RA measurements (Ghent et al 2016;Nypaver et al 2021).…”

Section: Interpretation Of Ra H-parameter and Cprmentioning

confidence: 61%

“…Conversely, a signal interacting with a rough or rocky region of the lunar surface will experience multiple scattering events, meaning more signal will be returned with the same-sense polarization and CPR will be closer to or greater than 1. A number of studies have used CPR to investigate surface and subsurface physical properties on the Moon (e.g., Carter et al 2009;Campbell 2012;Cahill et al 2014;Ghent et al 2016;Nypaver et al 2021), finding that rocky surfaces such as impact crater ejecta blankets and impact melt deposits have high CPR and that rock-poor surfaces such as pyroclastic deposits display low CPR. In this work we utilize both S1 (total power) and CPR data from Mini-RF and CPR data from Arecibo to investigate the surface and subsurface rock content of the red spots and compare with the Diviner RA and H-parameter results.…”

Section: Circular Polarization Ratiomentioning

confidence: 99%

“…Some of the red spots contain areas of high RA associated with volcanic vents, depressions, or hummocky terrain (e.g., Figures 10,11,and 12), and these areas generally also have high thermal inertia and high CPR, indicating that the terrain is rocky. Although the lifetime of rocks >1 m in diameter on the lunar surface is <1 Gyr (Ghent et al 2014;Basilevsky et al 2015), these areas likely remain rocky even after >3 Gyr because their rock population is replenished by mass wasting, which exposes fresh boulders when fine-grained material moves downslope (Nypaver et al 2021). However, most of the red spots are generally less rocky (with fewer rocky impact craters) than the surrounding maria (Figure 13).…”

Section: Materials Properties Of the Red Spotsmentioning

confidence: 99%

See 1 more Smart Citation

Evidence for Fine-grained Material at Lunar Red Spots: Insights from Thermal Infrared and Radar Data Sets

Byron,

Elder,

Glotch

et al. 2023

Planet. Sci. J.

View full text Add to dashboard Cite

Lunar red spots are small spectrally red features that have been proposed to be the result of non-mare volcanism. Studies have shown that a number of red spots are silicic, and are spectrally distinct from both highlands and mare compositions. In this work, we use data from LRO Diviner, Mini-RF, and Arecibo to investigate the material properties of 10 red spots. We create albedo maps using Diviner daytime solar reflectance data to use as an input to our improved thermophysical model, and calculate the rock abundance (RA) and H-parameter values that best fit Diviner nighttime thermal infrared radiance measurements. The H-parameter can be considered analogous to the thermal inertia of the regolith, with a high H-parameter corresponding to low thermal inertia. We find that the red spots generally have low RA, and do not have a uniform H-parameter but contain localized regions of high H-parameter. We additionally find that the red spots have a low circular polarization ratio (CPR) in many of the same locations that show a low RA and high H-parameter. Low RA, high H-parameter, and low CPR indicate a relative lack of rocks larger than ∼10 cm, which is consistent with previous findings of a mantling of fine-grained pyroclastic material for at least three red spots. Areas with high H-parameter but that do not show clear signs of pyroclastics in other data sets may be evidence of previously undiscovered pyroclastics, or could be due to the unique physical properties (e.g., porosity, rock strength/breakdown resistance) of the rocks that make up the red spots.

show abstract

“…These inter-crater regions included both the rims and interiors of all craters smaller than 1 km, which our study and the work of Elder et al (2019) have shown can have significant rock abundance signals. The Vanga et al (2022) conclusion of an inverse relationship of rockiness with time for inter-crater regions may be the result of contamination by small craters like those we study and the evolution of rocks within the interior and rims of craters, which are known to enhance a rock abundance signal over time (Nypaver et al, 2021). We have identified and characterized more <1 km rocky craters than were available to Vanga et al (2022).…”

Section: Discussionmentioning

confidence: 73%

The Rock Abundance of Crater Populations as a Probe of Mare Protolith Properties

et al. 2023

View full text Add to dashboard Cite

The volcanic parent rock (“protolith”) composing the lunar maria is likely to have developed diverse mechanical properties upon emplacement. The abundance of rocks ejected by impacts may be sensitive to protolith properties. We investigate the relationship between the possible diversity of mare protoliths and the abundance of rocks excavated and emplaced by impacts employing cumulative size‐frequency distributions (SFDs) of rocky craters in the maria. The SFDs of 15 mare units were calculated through varying degrees of Lunar Reconnaissance Orbiter Diviner‐derived rock abundance within crater ejecta blankets. By inspecting the frequency of high rock abundance craters, we find that the age of a surface does not control an impactor's ability to excavate rocks. Through analysis of SFDs, we find that differences in SFD behavior may act as probes for the mechanical strength of the protolith and the thickness of buried lava flows. Generally, regions with SFDs that have shallower slopes with increasing rockiness may be associated with thick, competent flow types, and regions with SFDs that have unchanging slopes with increasing rockiness may be associated with stacked, thin flows that are possibly more friable. The greater frequency of high rock abundance craters and the converging behavior of SFDs at two units within Mare Humorum and Oceanus Procellarum suggest that the surfaces are underlain by thick, competent lava flows. Finally, SFD slope analysis suggests that secondary impact craters are relatively ineffective at excavating rocks and the SFDs of rocky craters may reflect primary cratering populations.

show abstract

Prolonged Rock Exhumation at the Rims of Kilometer‐Scale Lunar Craters

Cited by 13 publications

References 42 publications

Rock Abundance on the Lunar Mare on Surfaces of Different Age: Implications for Regolith Evolution and Thickness

Rock Abundance on the Lunar Mare on Surfaces of Different Age: Implications for Regolith Evolution and Thickness

Evidence for Fine-grained Material at Lunar Red Spots: Insights from Thermal Infrared and Radar Data Sets

The Rock Abundance of Crater Populations as a Probe of Mare Protolith Properties

Contact Info

Product

Resources

About