Different Types of Gullies
NASA/JPL/University of Arizona
Different Types of Gullies
ESP_013948_1410  Science Theme: Fluvial Processes
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This image covers parts of two different craters, both with gullies in the inner walls. Gullies are a popular target because their formation is still being debated.

The powerful HiRISE camera reveals many details of gullies that have never been seen before. (Searching our catalog for "gully" or "gullies" will bring up many, many more images of gullies!) Some hypotheses about the formation of gullies involve the flow of some amount of liquid (water, brine, or some other substance), and others postulate that gullies could be formed by the downhill movement of dry material such as dust or sand. To further complicate things, different gullies could have formed by different methods.

The many gullies visible in this image look quite different from each other. This subimage from the southwestern part of the crater to the south shows a gully with a smaller alcove (source region at the top) and a deep main channel. The material in the channel is a different color than the alcove, indicating they may contain different minerals or different grain sizes.

Another gully in the north part of the same crater has almost no alcove and very little material deposited at the bottom. However, this gully is marked by a distinct bright-colored deposit along its length. This could be a sign of recent activity where material has moved downhill.

Yet another site nearby within the same crater has multiple overlapping gullies of different types. Most of these have large fan-shaped deposits at the bottom, and a few to the left side of the subimage have bright deposits where new material may have been deposited or exposed. Some of the channels and fans contain ripples; this might be where wind eroded loose material, or it may be a texture that formed as sand or liquid moved down the slope. Some of the gully-like features in this image are more likely dry landslide chutes.

This is also a good example of how we use lower-resolution data from other missions, like this previous MOC image, to target the HiRISE camera. A science team member studied the MOC image, and she decided more could be learned by getting a higher-resolution color picture of this site. Now studying this HiRISE image will teach us more about how gullies form.

For more information about gullies in HiRISE images, see these captions as well as many more images in our catalog:

PSP_010567_2360

PSP_007592_1425
Written by: Ingrid Daubar Spitale   (2 December 2009)

This is a stereo pair with ESP_013236_1410.

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Acquisition date
18 July 2009

Local Mars time:
14:24

Latitude (centered)
-38.695°

Longitude (East)
159.358°

Range to target site
262.5 km (164.1 miles)

Original image scale range
52.5 cm/pixel (with 2 x 2 binning) so objects ~158 cm across are resolved

Map projected scale
50 cm/pixel and North is up

Map projection
Equirectangular

Emission angle:
17.4°

Phase angle:
52.3°

Solar incidence angle
36°, with the Sun about 54° above the horizon

Solar longitude
305.4°, Northern Winter

North azimuth:
95°

Sub-solar azimuth:
26.1°
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All of the images produced by HiRISE and accessible on this site are within the public domain: there are no restrictions on their usage by anyone in the public, including news or science organizations. We do ask for a credit line where possible:
NASA/JPL/University of Arizona



Postscript
For information about NASA and agency programs on the Web, visit: http://www.nasa.gov. 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. Lockheed Martin Space Systems is the prime contractor for the project and built the spacecraft. The HiRISE camera was built by Ball Aerospace and Technology Corporation and is operated by the University of Arizona. The image data were processed using the U.S. Geological Survey’s ISIS3 software.