Gale crater and impact processes – Curiosity’s first 364 Sols on Mars

• Published in: Icarus (New York, N.Y. 1962) Vol. 249; pp. 108 - 128
• Main Authors: Newsom, Horton E., Mangold, Nicolas, Kah, Linda C., Williams, Joshua M., Arvidson, Ray E., Stein, Nathan, Ollila, Ann M., Bridges, John C., Schwenzer, Susanne P., King, Penelope L., Grant, John A., Pinet, Patrick, Bridges, Nathan T., Calef, Fred, Wiens, Roger C., Spray, John G., Vaniman, David T., Elston, Wolf E., Berger, Jeff A., Garvin, James B., Palucis, Marisa C.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-03-2015
• Subjects: Atmosfärsvetenskap; Atmospheric Science; Cratering; Ejecta; Erosion; Impact processes; Mars craters; Mars rovers; Mars surface; Sols; Surface layer; Surfacing; Texture; Impact processes; Mars, surface; Cratering
• ISSN: 0019-1035; 1090-2643; 1090-2643
• DOI: 10.1016/j.icarus.2014.10.013

•Impact crater processes observed during MSL’s first 360 Sols were studied.•Possible impactites are scarce, but include shatter cones and disrupted bedrock.•Loose igneous and sedimentary blocks identified near the rover may be distal ejecta.•The smallest observed crater is 0.6m in diam., consistent with atmospheric filtering.•Crater counts constrain the aeolian erosion rate to ~10mm per million years.•The erosion rate is consistent with the observed erosion of the Peace Vallis fan.
Impact processes at all scales have been involved in the formation and subsequent evolution of Gale crater. Small impact craters in the vicinity of the Curiosity MSL landing site and rover traverse during the 364 Sols after landing have been studied both from orbit and the surface. Evidence for the effect of impacts on basement outcrops may include loose blocks of sandstone and conglomerate, and disrupted (fractured) sedimentary layers, which are not obviously displaced by erosion. Impact ejecta blankets are likely to be present, but in the absence of distinct glass or impact melt phases are difficult to distinguish from sedimentary/volcaniclastic breccia and conglomerate deposits. The occurrence of individual blocks with diverse petrological characteristics, including igneous textures, have been identified across the surface of Bradbury Rise, and some of these blocks may represent distal ejecta from larger craters in the vicinity of Gale. Distal ejecta may also occur in the form of impact spherules identified in the sediments and drift material. Possible examples of impactites in the form of shatter cones, shocked rocks, and ropy textured fragments of materials that may have been molten have been observed, but cannot be uniquely confirmed. Modification by aeolian processes of craters smaller than 40m in diameter observed in this study, are indicated by erosion of crater rims, and infill of craters with aeolian and airfall dust deposits. Estimates for resurfacing suggest that craters less than 15m in diameter may represent steady state between production and destruction. The smallest candidate impact crater observed is ∼0.6m in diameter. The observed crater record and other data are consistent with a resurfacing rate of the order of 10mm/Myr; considerably greater than the rate from impact cratering alone, but remarkably lower than terrestrial erosion rates.