Analyzing the ages of south polar craters on the Moon: Implications for the sources and evolution of surface water ice.

Deutsch, A. N.; Head, J. W.; Neumann, Gregory A.

doi:10.1016/j.icarus.2019.113455

Cited by 62 publications

(54 citation statements)

References 55 publications

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“…Even a 5 m thick deposit that was emplaced 1 Gyr ago would not have been gardened in its entirety and should still appear radar‐bright. If the Moon ever had Mercury‐like deposits they must have been ancient (e.g., Deutsch et al, ; Needham & Kring, ), and therefore subject to the orders of magnitude higher impact environment before the Copernican era or buried.…”

Section: Discussionmentioning

confidence: 99%

Impact Gardening as a Constraint on the Age, Source, and Evolution of Ice on Mercury and the Moon

et al. 2020

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We update an analytic impact gardening model (Costello et al., 2018, https://doi.org/10.1016/j.icarus.2018.05.023) to calculate the depth gardened by impactors on the Moon and Mercury and assess the implications of our results for the age, extent, and source of water ice deposits on both planetary bodies. We show that if the water presently on the Moon has a primordial origin, it may have been 4–15 m thick. If ice deposits are buried, they may be as shallow as 3 cm or as deep as 10 m and provide a gradient of probability for ice gardened into a column. Our calculations for gardening on Mercury show that thermal lag deposits will be reworked into the background over 200 Myr, and, thus, the most recent large‐scale deposition of ice on Mercury must have occurred no more than 200 Myr ago. We also find that gardening mixes incremental layers of ice with underlying regolith and prevents the growth of pure ice deposits by continuous supply. We conclude that ice deposits on the Moon and Mercury are likely the result of sudden and voluminous deposition.

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Section: Discussionmentioning

confidence: 99%

Impact Gardening as a Constraint on the Age, Source, and Evolution of Ice on Mercury and the Moon

et al. 2020

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“…Based on these same crater counting methods (the supporting information), we dated 43 new large crater floors at the north pole between 80°and 90°N (Table S2) using the CraterStats II program (Michael & Neukum, 2010). We also updated the model age of Cabeus crater at the south pole from 3.5 Ga (Deutsch et al, 2020) 10.1029/2020GL088920…”

Section: Ejecta Emplacementmentioning

confidence: 99%

“…Impact effects have been considered for micrometeoroids (e.g., Farrell et al, 2019) and small impactors (Cannon & Britt, 2020; Costello et al, 2020; Crider & Vondrak, 2003; Hurley et al, 2012). The large polar craters (>20 km diameter) each formed at a distinct point in lunar history (Deutsch et al, 2020; Tye et al, 2015), and during crater formation, these impacts would have emplaced ejecta out to significant distances (e.g., McGetchin et al, 1973), affecting existing ice deposits in the surrounding terrains. These effects included mixing and burial through ballistic sedimentation (Oberbeck, 1975), potential melting and vaporization (Weiss & Head, 2016), and even possible aqueous alteration (Stopar et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Stratigraphy of Ice and Ejecta Deposits at the Lunar Poles

Cannon

Deutsch

Head

et al. 2020

Geophysical Research Letters

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Water ice has been delivered to the lunar poles from different sources over billions of years, but this accumulation was punctuated by large impacts that excavated dry regolith from depth and emplaced it in layers over the poles. Here, we model the resulting stratigraphies of ice and ejecta deposits in the lunar polar regions. Large polar craters were age dated, and their ejecta distributions calculated with standard scaling relations. We then created a Monte Carlo model for ice deposition and ejecta emplacement. Typical model runs showed that deposits in older cold traps (>4 Ga) are divided into two zones: buried ice-rich gigaton deposits and younger more gardened mantles. The latter are consistent with small crater morphometry measurements, but the existence of substantial ice buried at great depths is more difficult to confirm. Rare outlier model runs included Mercury-like cases with significant deposition events in recent history (<200 Ma). Plain Language Summary The polar regions of Earth's Moon have topographic depressions that are never directly exposed to the Sun, so they are cold enough for deposits of ice to exist. Water can get into these regions by water-bearing asteroids colliding with the Moon, or from lunar volcanoes erupting gases that travel to the poles. At the same time, large impact craters that form at the poles eject an enormous amount of soil and rock that could bury existing ice. It is not well understood how these two processes work together to build up deposits that may have alternating layers of ice-rich and ice-poor soil. In this study, we used computer simulations to predict what these layered deposits may look like. We found it is likely that large amounts of relatively pure ice are buried at depth in the oldest deposits, covered with thinner layers hosting less ice. Impact cratering has been the dominant process affecting the lunar poles, but the effects of large polar craters on nearby ice deposits have not been previously addressed. Impact effects have been considered for micrometeoroids (e.g.,

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“…Perhaps, all these sources would have played a role in the lunar water record in the course of lunar evolution. Deutsch et al 2019 dated the south polar craters where surface water ice is present, and examined the relationship between the water ice deposits in each crater and the crater age. The water-ice-rich craters dated back to !~3.1 Ga (Deutsch et al 2019).…”

Section: Lunar Volatilesmentioning

confidence: 99%

“…Deutsch et al 2019 dated the south polar craters where surface water ice is present, and examined the relationship between the water ice deposits in each crater and the crater age. The water-ice-rich craters dated back to !~3.1 Ga (Deutsch et al 2019). Recently, LAMP (Lyman Alpha Mapping Project) in NASA's LRO mission provided significant evidences for the migration of water molecules around the dayside of the Moon (Hendrix et al 2019).…”

Section: Lunar Volatilesmentioning

confidence: 99%