Evidence of Multiple Episodes of Gully Formation
Evidence of Multiple Episodes of Gully Formation
PSP_001684_1410  Science Theme: Fluvial Processes
This observation shows gullies in a crater in Terra Sirenum. The gullies unusually emanate from different elevations along the crater wall. Several of the gullies are extremely developed and incised, while others have very narrow, shallow channels.

Many of the gullies appear to have extensive debris aprons, but that could be deceiving. Based on their surroundings, the topography underlying the debris aprons is likely not flat or gently sloping. This might cause the debris apron material to cover a wider surface area, without being as large of a volume as it might appear visually, than it otherwise would.

The subimage shows a gully with many channels. Several of the channels overlap or are overlapped by debris aprons suggesting that multiple flow episodes occurred here. In particular, there is a large channel that sticks out from underneath the main debris apron with a debris apron of its own. If this channel originated where the alcove currently is, then it is possible that the past flow contained more liquid and that the source of liquid to form the gullies in this region is now available in smaller amounts for an unknown reason.

Written by: Kelly Kolb  (31 January 2007)

This is a stereo pair with PSP_002027_1410.
Acquisition date
05 December 2006

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
250.8 km (155.9 miles)

Original image scale range
25.3 cm/pixel (with 1 x 1 binning) so objects ~76 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection

Emission angle

Phase angle

Solar incidence angle
74°, with the Sun about 16° above the horizon

Solar longitude
145.8°, Northern Summer

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  39.1°
Black and white
map projected  non-map

IRB color
map projected  non-map

Merged IRB
map projected

Merged RGB
map projected

RGB color
non-map projected

Black and white
map-projected   (306MB)

IRB color
map-projected   (169MB)

Black and white
map-projected  (136MB)
non-map           (178MB)

IRB color
map projected  (37MB)
non-map           (145MB)

Merged IRB
map projected  (68MB)

Merged RGB
map-projected  (67MB)

RGB color
non map           (121MB)
Map-projected, reduced-resolution
Full resolution JP2 download
Anaglyph details page

B&W label
Color label
Merged IRB label
Merged RGB label
EDR products

IRB: infrared-red-blue
RGB: red-green-blue
About color products (PDF)

Black & white is 5 km across; enhanced color about 1 km
For scale, use JPEG/JP2 black & white map-projected images

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

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.