Assessing the Roughness Properties of Circumpolar Lunar Craters: Implications for the Timing of Water‐Ice Delivery to the Moon. Issue 15 (4th August 2020)

• Record Type: Journal Article
• Authors: Deutsch, Ariel N.; Head, James W.; Neumann, Gregory A.; Kreslavsky, Mikhail A.; Barker, Michael K.
• Is Part Of: Geophysical research letters. Volume 47:Issue 15(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-08-04
• Subjects: Moon -- roughness -- impact craters -- ice -- polar -- LOLA; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2020GL087782
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The roughness properties of impact craters are valuable indicators of crater degradation and can provide insight into crater ages. We evaluate the roughness of lunar craters from different geologic eras, confirming that young, Copernican craters are distinctly rougher than older craters. We evaluate the potential age of small (less than ~15 km) craters that are thought to host surface ice by quantifying the roughness inside these craters, as well as outside. Interior roughness may be subdued by slope processes or the presence of volatiles. The distribution of ice‐bearing craters is skewed toward roughness values higher than those of pre‐Imbrian craters, although no ice‐bearing craters are within the Copernican‐only domain in roughness space. All of the 15 rough, permanently shadowed craters that are found within the Copernican‐only domain lack water‐ice detections, suggesting that either ice has not been delivered to these young craters or that it has since been destroyed. Plain Language Summary: When a planetary surface is struck by an impactor, the preexisting surface is disturbed as rocks and boulders scatter from the high‐energy collision. Over time, the surface texture becomes smoother as these rocks and boulders are broken up into smaller pieces and begin to diffuse away. Surface texture is thus a powerful tool for evaluating the degradation of impact craters, given that young, fresh craters tend to be rougher than old craters due to the presence of rocks and boulders on the recently disturbed surface. Here we quantify the surface texture of lunar craters of different geologic eras and establish a relationship between the roughness and age of craters. We evaluate the roughness of small craters that host near‐polar surface ice and find a population of craters likely to be post‐Nectarian in age. However, the youngest polar craters lack surface ice detections. Key Points: Copernican craters have distinctly rougher interiors and exteriors than older craters Some small ice‐bearing craters are rougher than pre‐Imbrian craters and surface ice within them was likely delivered post‐Nectarian The roughest polar craters appear to be Copernican and lack surface ice detections