Assessing the habitability of Mars using impact crater statistics

Because Mars lacks a global magnetic field or protective ozone layer, its surface is unshielded to harsh radiation from space. This ionizing radiation breaks down any organic components in the soil at the martian surface on timescales of tens to hundreds of millions years (10–100 Ma). In planetary geology, we use the density of impact craters as a proxy for time: older surfaces tend to accumulate more craters. Using impact craters, we can assess the exposure age and therefore organic preservation potential of the Martian surface from orbit. The goal of this ongoing project is to better understand exposure ages and organic preservation potential across Mars by analyzing the size-frequency distribution of impact craters at selected sites across the surface. Specifically, we use JMARS, a GIS program developed by ASU’s Mars Space Flight Facility [Christensen et al., 2009], to examine CTX (Context Camera) images of Mars in a gridded array over Mars so that we can document the density of craters between 100 m and 1 km in diameter, which are the most susceptible to erosion. The data for the collected craters is then analyzed on CraterStats, a crater counting analysis software by the Freie Universität Berlin [Michael, 2013], where we document the transition diameter between erosion and production. Preliminary results [Thomson, 2018] indicate that at high latitudes greater than about ±45° N and S, fewer small diameter craters are present than at regions closer to the equator, indicating more active erosion. This latitudinal pattern is consistent with other observed surface parameters, such as the depth to diameter ratio of 3-5 km diameter craters [Robbins and Hynek, 2012] and the surface roughness measured in MOLA (Mars Orbital Laser Altimeter) profiles [Kreslavsky and Head, 2000]. References: Christensen, P., E. Engle, S. Anwar, S. Dickenshied, D. Noss, N. Gorelick, and M. Weiss-Malik (2009), JMARS-a planetary GIS, AGU Fall Meeting, Abstract #IN22A-06. Kreslavsky, M. A., and J. W. Head (2000), Kilometer-scale roughness of Mars: Results from MOLA data analysis, JJournal of Geophysical Research, 105, 26,695–26,712. Michael, G. G. (2013), Planetary surface dating from crater size–frequency distribution measurements: Multiple resurfacing episodes and differential isochron fitting, Icarus, 226(1), 885-890, properties and regional variations of the simple-to-complex transition diameter, Journal of Geophysicaldoi:10.1016/j.icarus.2013.07.004. Research, 117(E6), doi:10.1029/2011JE003967. Robbins, S. J. and B. M. Hynek (2012), A new global database of Mars impact craters ≥ 1 km: 2. Global crater Thomson, B. J. (2018), Erosion Rates on Mars: Relevance to Astrobiology, Lunar and Planetary Science Conference, 49, abstract #1788