Geezer Gullies at Tempe Terra
NASA/JPL-Caltech/UArizona
Geezer Gullies at Tempe Terra
ESP_017015_2245  Science Theme: Glacial/Periglacial Processes
This image shows gullies in the walls of a large impact crater in Tempe Terra. These gullies look quite older than other gullies imaged by HiRISE elsewhere on Mars.

We cannot tell what is the absolute age of these “geezer gullies” (that is, how long ago they formed), because actual rock samples would have to be analyzed with radiometric dating techniques to get that information. However, this image indicates that they have been inactive for a long time.

This subimage shows some of these gullies in detail. The walls of these venerable gullies have gentle, smooth-looking slopes which contrast with the tall and steep walls of younger gullies. Their floor is even and lacks sharply incised channels that would indicate recent activity. The weathering processes required to produce such a smooth landscape are very slow and thus must have acted during a long period of time.

The gullies appear cut by long fractures that criss-cross the crater’s walls, and pockmarked by numerous impact craters which are just a few meters (yards) in diameter. According to cross-cutting relationships (used by geologists, archaeologists, and other detective-types to establish relative ages), this means that the gullies must be older than the fractures and small craters. Crater counting is a valuable technique used to estimate the relative age of terrains on Mars and other planetary surfaces; the more time a terrain has been exposed at the surface, the more craters it has accumulated.

The color and brightness of the gullies is similar to that of their surroundings, probably due to a veneer of undisturbed, homogeneous dust mantling the entire region.

All these lines of evidence indicate that these gullies have remained inactive for a long period of time. Why are they “dormant,” while other Martian gullies appear to show recent activity? Studying both old and young gullies will help us learn more about their processes of formation (erosion from seepage of subsurface water? melting of ground ice or surface snow? dry landslides?). Their differences will tell us how these processes (many of which depend on Mars’ climate) may have evolved through time.

Written by: Sara Martinez-Alonso  (5 May 2010)
 
Acquisition date
14 March 2010

Local Mars time
14:55

Latitude (centered)
44.036°

Longitude (East)
299.191°

Spacecraft altitude
298.1 km (185.2 miles)

Original image scale range
29.9 cm/pixel (with 1 x 1 binning) so objects ~90 cm across are resolved

Map projected scale
25 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
3.1°

Phase angle
45.0°

Solar incidence angle
42°, with the Sun about 48° above the horizon

Solar longitude
63.8°, Northern Spring

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  349.0°
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   (966MB)

IRB color
map-projected   (426MB)

JP2 EXTRAS
Black and white
map-projected  (505MB)
non-map           (409MB)

IRB color
map projected  (130MB)
non-map           (312MB)

Merged IRB
map projected  (227MB)

Merged RGB
map-projected  (219MB)

RGB color
non map           (306MB)
BONUS
4K (TIFF)
8K (TIFF)
10K (TIFF)

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-Caltech/UArizona

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.