Ices

a b s t r a c t Martian glacier-like forms (GLFs) indicate that water ice has undergone deformation on the planet within its recent geological past, but the driving mechanisms behind the origin, evolution and dynamics of these landforms remain poorly understood. Here, we present the results of a comprehensive inventory of GLFs, derived from a database of 8058 Context Camera (CTX) images, to describe the physical controls on GLF concentration and morphometry. The inventory identifies 1309 GLFs (727 GLFs in the northern hemi-sphere and 582 in the southern hemisphere) clustered in the mid-latitudes (centred on a mean latitude of 39.3! in the north and!40.7! in the south) and in areas of rough topography. Morphometric data show inter-hemispheric similarity in GLF length (mean = 4.66 km) and width (mean = 1.27 km), suggesting a common evolutionary history, and a poleward orientation of GLFs in both hemispheres, indicating a sen-sitivity to climate and insolation. On a local scale, elevation is shown to be the most important control on GLF location, with most GLFs occurring above an altitude threshold of!3000 m (AOD), and in areas of moderate, but not high, relief. We propose, therefore, that martian GLFs may not exhibit accumulation or ablation areas as is the norm for terrestrial glacial systems, but reflect ice motion in response to local relief within a widely distributed reservoir of ice deposited within prescribed latitudinal and elevational ranges. " 2011 Elsevier Inc. All rights reserved. 1