Sinuous Ridge in Argyre Planitia
NASA/JPL/University of Arizona
Sinuous Ridge in Argyre Planitia
ESP_014272_1245  Science Theme: Glacial/Periglacial Processes
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Though a variety of origins have been proposed, this sinuous, layered, boulder-filled deposit in the southern Argyre Planitia is likely an esker. Eskers form in wet-based glaciers, when water flows inside or below the glaciers and deposits sediment. After the ice melts, the sediment is left behind as a ridge.

Because the material is deposited by flowing water, the sediment in eskers is sorted: larger rocks, pebbles, sand grains, etc. are deposited first, and smaller sediment, such as smaller pebbles, sand, or clay, are deposited further from the source and on top of the coarser material. Several factorsóincluding the amount of sediment available, the speed and volume of the flowing water, and the slope over which it flowedódetermine how much sediment is deposited and how large the dominant grain size is. There may be many of these sequences preserved within an esker.

Eskers look a little like inverted river beds. One relatively simple way to differentiate between the two is that inverted river beds record flow in a downhill direction along their entire length. Eskers, on the other hand, can record flow both down- and uphill. This is possible because water flowing through the ice tunnels in glaciers is under pressure, just like water in a hose.

This particular esker is part of a branching and braided network of ridges in the southern Argyre basin. The boulders are on the order of 1-3 meters (about 3-10 feet) in diameter.

Written by: Andrea Philippoff  (16 September 2009)
 
Acquisition date
12 August 2009

Local Mars time
14:35

Latitude (centered)
-55.374°

Longitude (East)
319.352°

Spacecraft altitude
255.0 km (158.5 miles)

Original image scale range
25.7 cm/pixel (with 1 x 1 binning) so objects ~77 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
7.4°

Phase angle
44.6°

Solar incidence angle
49°, with the Sun about 41° above the horizon

Solar longitude
320.1°, Northern Winter

For non-map projected images
North azimuth:  98°
Sub-solar azimuth:  44.1°
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POSTSCRIPT
NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif., manages the Mars Reconnaissance Orbiter for NASA’s Science Mission Directorate, Washington. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona.