A new class of Mars gullies.

In this sci.astro post I noted unusual parallel trending ridges in an
MGS image of the Tharsis region:

Newsgroups: sci.astro, sci.geo.geology
From: ("Robert Clark")
Date: Mon, 26 Mar 2001 11:15:32 +0000 (UTC)
Local: Mon, Mar 26 2001 6:15 am
Subject: Strange features in Martian craters in Tharsis.
http://groups.google.com/group/sci.a...1bd9437ae5ff52

The ridges appear on the rims of craters, inside craters and within
the channel in the image as well:

http://ida.wr.usgs.gov/fullres/divid.../m0301739d.jpg

http://ida.wr.usgs.gov/fullres/divid.../m0301739a.jpg

The ridges have the appearance of de Geer or Rogen moraines on Earth:

Structure of the De Geer moraine and large transversal moraine
ridge at Björköby and Köklot.
http://www.ymparisto.fi/download.asp...d=34282&lan=sv

Geonat-project 2003 -2006.
http://en.gtk.fi/export/sites/defaul...at_nettiin.pdf

Moraines.
http://gsc.nrcan.gc.ca/landscapes/pdf/moraines_e.pdf

Rogen moraine: an example of glacial reshaping of pre-existing
landforms.
http://www.geol.lu.se/personal/prm/P...2006_Rogen.pdf

A close look at the ridges in the MGS image shows linear indentations
cross-wise across their tops. These indentations were mysterious but a
Mars Reconnaissance Orbiter image of a region showing similar parallel
ridges shows indentations on the ridges that are channels:

Layers with Boulders in Aeolis Region.
http://hiroc.lpl.arizona.edu/images/...P_001448_1735/

Look at the highest resolution version available on this page (328
Mbytes) to see the channels running down from the tops of the ridges.
This MRO image is not of the same area as the MGS image, in fact it's
on the other side of the planet from Tharsis, but I believe the images
show the same type of feature.
The channels have the appearance of water carved features. If the
ridges are analogues of moraines then they may be due to melting ice.
The boulders in the image may also be glacial erratics, boulders
pushed along by the movement of glacial ice.
Moraines can be ice-cored. And the cover of dirt and debris in a
moraine can preserve the ice from melting after the original glacier
has melted:

Paper No. 33-0
SEDIMENT CHARACTERISTICS OF DIFFERENT TYPES OF ICE-CORED MORAINES,
MATANUSKA GLACIER, ALASKA
HEYER, Sean, Geology Department, Augustana College, 639 38th St, Rock
Island, IL 61201, .
http://gsa.confex.com/gsa/2002NC/fin...ract_32762.htm

Recent research has suggested there may be current remnant ice in
Tharsis:

Space Sciences
Current glaciers in Tharsis?
Posted by Robert Clark on 11/23/2002 7:26:23 AM
http://habitablezone.com/space/messages/236285.html

Formation of Glaciers on Mars by Atmospheric Precipitation at High
Obliquity.
F. Forget,1* R. M. Haberle,2 F. Montmessin,3 B. Levrard,4 J. W. Head5
Science, 20 January 2006: Vol. 311. no. 5759, pp. 368 - 371
http://www.sciencemag.org/cgi/content/full/311/5759/368

The theory is that a debris cover has preserved the ice from melting
in this near equatorial region.
Aeolis is contained in the Elysium region which has also been argued
might contain relict ice:

Extent and further characteristics of former glaciated terrain in
Elysium Planitia, Mars.
J. Nussbaumer, Department of Mineralogy, Natural History Museum,
London, UK, .
Lunar and Planetary Science XXXVI (2005) 1949.pdf
http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1949.pdf

Modern shelf ice, equatorial Aeolis Quadrangle, Mars.
Brakenridge, G. R.
Dartmouth Coll., Hanover, NH.
Lunar and Planetary Inst., Twenty-fourth Lunar and Planetary Science
Conference. Part 1: A-F p 175-176 (SEE N94-12015 01-91)
http://adsabs.harvard.edu/abs/1993LPI....24..175B



Bob Clark