Post by Dr. Mikhail Kreslavsky¹ and Prof. James Head²

¹Assistant Research Planetary Scientist, UC Santa Cruz, USA. ²Planetary geosciences group, Brown University, Providence, Rhode Island, USA.

On Earth, cold-based glaciers (glaciers deforming internally, without basal melting and basal sliding) are found in the coldest environments (e.g., Antarctica, Marchant et al., 1993). Unlike the majority of glaciers, cold-based glaciers do not scour their substrate and leave pre-glacier topography unaffected. When cold-based glaciers advance and then dynamically stabilize (the ice flow is balanced by frontal ice ablation); debris carried forward by the glacier drops out at the glacial fronts as sublimation of the ice occurs; the dropped material produces so-called drop moraines.

In three locations at high northern latitudes of Mars, overlapping small ridges of arcuate planforms associated with slopes were interpreted as drop moraines left by extinct cold-based glaciers (Garvin et al., 2006; Kreslavsky and Head, 2011). Image 1 shows one of these locations, where a presumable glacier was formed at south-eastern part of an impact crater rim. The shapes of the extinct glacial lobes around the central peak of the crater suggest a few hundred meters thickness of the glacier.

Image 1: Unnamed impact crater in the Northern Lowlands on Mars at 70.3oN, 266.5oE with loop-shaped ridges interpreted as drop moraines created by carbon dioxide glaciers. Image captured by Context Camera onboard Mars Reconnaissance Orbiter, image number T01_000876_2505 Illumination is from lower left.

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Post by Daniela Tirsch.

Glacial and fluvial landforms that date to ancient Noachian and Hesperian times indicate an abundance of liquid water on Mars at that time. Of interest is evidence of younger (i.e., Amazonian) glacial activities. These processes have recently been suggested for some locations in the Marmers Valles region of Mars [Kress et al., 2006; Di Achille and Ori, 2008; Tirsch, 2009a] (Image 1).

Image 1: Crater near Mamers Valles (HRSC orbit 3304, perspective view, north is to the left).

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Posted by Dr. Ernst Hauber

Lobate debris aprons (LDA) are distinctive geomorphic landforms showing evidence for the creep and deformation of ice-rich debris in Martian mid-latitudes [e.g., Carr and Schaber, 1977; Squyres, 1978, 1979; Lucchitta, 1984].

Image 1: The image shows a textbook example of a typical Martian lobate debris apron, considered to be a mixture of ice and rocky particles (rock glaciers are a terrestrial analog). The lobate flow front and the convex-upward profile are characteristic for these phenomena. The data were acquired on May 29, 2004 with the Mars Express High Resolution Stereo Camera (HRSC). The 3D-perspective in this image was rendered to simulate an oblique view from the north. The mountain with the lobate debris apron is centered at 40.60 S and 103.01 E, in the Promethei Terra region, very close to Reull Vallis.

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