Effect of obliteration on crater‐count chronologies for Martian surfaces

Abstract

The density of impact craters calibrated against lunar data is currently the only quantitative measure of surface age for terrestrial planetary surfaces. Unlike the Moon, however, Mars has been weathered and eroded, obliterating some small (<10 km diameter) craters, a phenomenon addressed in the Mariner/Viking days of Mars exploration but commonly overlooked in recent studies. We present a quantitative model that extends this earlier work to assess the effect of erosion and infilling on surface ages inferred from crater‐frequency distributions. Our work affirms that small‐crater size distributions can be interpreted quantitatively in terms of effects of erosion and crater infilling at rates comparable to those reported for Mars. A reanalysis of prior studies indicates that low to moderate long‐term rates of erosion and crater infilling can mask an ancient age and result in small‐crater populations similar to those offered as evidence for young and geologically significant surface activity.