The effects of crater degradation and target differences on the morphologies of Martian complex craters

We compared the target types and the morphologies and morphometries of various features within fresh complex craters on Mars to assess target dependence. The wide scatter in depth-diameter data from Martian craters is more pronounced than for lunar or Mercurian craters. This was previously assumed to be predominantly due to significant degrees of denudation and secondary infilling of the Martian craters. However, our data for fresh craters still exhibit a wide variation, which we interpret to be the result of comparatively higher target heterogeneity on Mars. Complex central peaks exhibit some crater diameter dependence, preferentially occurring in craters >50 km. Neither peak complexity nor geometry shows any statistical correlation with target type. Although central peak heights and aspect ratios do not exhibit any clear target dependence, they do appear to be correlated-higher peaks possess narrower aspect ratios. Floor and summit pits appear to be more common on lava targets than sedimentary targets, contrary to earlier studies with smaller sample sizes. This observation imposes additional constraints on models proposed for the origin of pits, especially those models that require the presence of volatiles in the target. The ability to correlate target type with crater morphologies/ morphometries is highly contingent upon both the surface geology and the actual geology at depth. Some weak correlations may reflect our current limited understanding of the subsurface geology of Mars. Information on the deeper lithologies acquired through future missions may help resolve the true effect of subsurface competence on intracrater structure. © 2010 The Geological Society of America. All rights reserved.