Recent high-latitude resurfacing by a climate-related latitude-dependent mantle Constraining age of emplacement from counts of small craters

A surficial mantling deposit composed of ice and dust blankets Mars at high and mid-latitudes. The emplacement and evolution of this deposit is thought to be driven by astronomical forcings akin to, but more extreme than, those responsible for Earth’s ice ages. In order to test predictions about the age of this deposit, more than 60,000 superposed craters were counted on terrain near the rims of 16 young craters using sub-meter resolution images. A chronology for the deposition of the latitude-dependent mantle is revealed by these data and shows that: (1) the overall age and age trend of mantling deposits is consistent with first-order control by obliquity variations; (2) mantling processes are substantially younger than some equatorial rayed craters which have crater retention ages of 20–30 million years; (3) the mantle is younger by a factor of two to three at polar latitudes compared to its furthest equatorial extent ( 301). Additionally, these crater counts confirm the suitability of small craters in geological analyses of youthful planetary surfaces and provide new data on the density of meters-scale craters superposed on deposits of geologically-recent craters. & 2012 Elsevier Ltd. All rights reserved.