NASA Mars Picture of the Day: Alcoves in a Xanthe Crater

Mars Global Surveyor Mars Orbiter Camera

MGS MOC Release No. MOC2-715, 3 May 2004

NASA/JPL/Malin Space Science Systems

Martian middle- and polar-latitude gullies are not the
only places that ‘alcoves’ form by downslope erosion
of debris. Even at equatorial latitudes, some
craters exhibit these features. Alcoves at the
heads of narrow, dry landslide scars are indicated
in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC)
image of a crater wall in Xanthe Terra. In both the
middle/polar-latitude gully cases and in this example, alcoves
form by undermining and collapse of material high on a relatively
steep slope such as a crater wall. In this case, however, no
fluid was involved, thus no gully or distinct apron formed.
This crater wall is located near Shalbatana Vallis around
2.7°N, 43.1°W. The image
is illuminated from the left, and
covers an area about 3 km (1.9 mi) across.
For comparison, an example of martian gullies with alcoves, channels, and
aprons can be seen in:
Evidence for Recent Liquid Water on Mars: Basic Features of Martian Gullies, 22 June 2000.

Malin Space Science Systems and the California Institute of Technology
built the MOC using spare hardware from the Mars Observer mission.
MSSS operates the camera from its facilities in San Diego, California.
The Jet Propulsion Laboratory’s Mars Surveyor Operations Project
operates the Mars Global Surveyor spacecraft with its industrial
partner, Lockheed Martin Astronautics, from facilities in Pasadena,
California and Denver, Colorado.