Multiple Levels of Gullies
NASA/JPL/University of Arizona
Multiple Levels of Gullies
PSP_004085_1420  Science Theme: Fluvial Processes
twitter  •  tumblr
This image shows groups of gullies at different elevations on the same crater wall. Although gullies are common in the mid-latitudes of Mars, they are rarely found to exist at such distinct elevations as seen here.

The mounds on the floor, one of which contains gullies, probably formed during a late stage of crater formation. Both levels of gullies appear to originate at layers. These layers might be ice-rich, or they might be capable of conducting water to the surface.

The gullies visible here are good candidates for formation by subsurface water, as opposed to melting ice or snow originating on the surface. The rounded, theater-shaped alcove and tributary heads are typical of features formed by groundwater sapping on Earth. Surface runoff does not form this morphology.

This image contains possible evidence of subsurface piping, when soil pores connect to form a "pipe" that transports water. When piping occurs, water carries soil with it, leaving empty space beneath the surface. As this process continues, the overlying surface can no longer support itself, and it collapses to form a depression. Several depressions that could have formed this way are visible in this image. The depressions are also directly upslope of more developed alcoves. They also originate at upslope layers, and might be examples of developing alcoves.

Written by: Kelly Kolb  (8 December 2008)

This is a stereo pair with PSP_004019_1420.
 
Acquisition date
10 June 2007

Local Mars time
15:21

Latitude (centered)
-37.898°

Longitude (East)
169.555°

Spacecraft altitude
252.4 km (156.9 miles)

Original image scale range
26.9 cm/pixel (with 1 x 1 binning) so objects ~81 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
20.6°

Phase angle
24.8°

Solar incidence angle
45°, with the Sun about 45° above the horizon

Solar longitude
255.0°, Northern Autumn

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  10.1°
JPEG
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

JP2
Black and white
map-projected   (739MB)

IRB color
map-projected   (367MB)

JP2 EXTRAS
Black and white
map-projected  (349MB)
non-map           (393MB)

IRB color
map projected  (130MB)
non-map           (305MB)

Merged IRB
map projected  (191MB)

Merged RGB
map-projected  (182MB)

RGB color
non map           (307MB)
ANAGLYPHS
Map-projected, reduced-resolution
Full resolution JP2 download
Anaglyph details page

ADDITIONAL INFORMATION
B&W label
Color label
Merged IRB label
Merged RGB label
EDR products
HiView

NB
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

USAGE POLICY
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
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.