A recent ice age on Mars: Evidence for climate oscillations from regional layering in mid-latitude mantling deposits

Two end-member hypotheses have been proposed to account for the emplacement and distribution of ice in the near-subsurface of Mars at mid to high latitudes during recent spin-axis/orbital variation-induced climate change. In the first, diffusion of atmospheric water vapor into and out of a porous regolith forms ice-cemented soils whose latitudinal stability migrates as a function of orbitally controlled climatic conditions. In the alternative hypothesis, atmospheric deposition of ice, snow, and dust produces dusty ice-rich layers during periods of higher obliquity. New image data reveal meters-thick layered deposits exposed on mid-latitude pole-facing slopes supporting the latter hypothesis. These observations suggest that the near surface ice detected by the GRS instrument suite and the Phoenix lander at high latitudes is linked to thick, buried ice that was atmospherically deposited during recent ice ages and that significant amounts of subsurface ice may remain today in the 30-50° mid-latitude regions where fresh craters, imaged by HiRISE, expose abundant ice.