Monitoring Dune Gullies
NASA/JPL/UArizona
Monitoring Dune Gullies
ESP_026506_1300  Science Theme: Aeolian Processes
There are landforms called "gullies," consisting of an alcove, channel, and apron, on many large sand dunes on Mars.

Remarkably, we have learned that the gullies form primarily or entirely during seasons when there is carbon dioxide frost on the ground. To understand this better we image key locations multiple times throughout the Martian year.

This image, at 49.5 S latitude, was acquired very near the winter solstice, when shadows are very long in the middle afternoon when MRO passes overhead. Dark sand inside shadows is a challenging scene to image while flying overhead at 3.4 km/sec, but the HiRISE camera has the sensitivity needed to acquire useful images even at the most challenging time of the year.

The subimage shows one of these gullies, hidden in the shadow. Vertical stripes in the image are from electronic noise that is usually hidden by the image signal, but in this case the signal is extremely low.



Written by: Alfred McEwen  (16 May 2012)
 
Acquisition date
22 March 2012

Local Mars time
15:21

Latitude (centered)
-49.504°

Longitude (East)
34.848°

Spacecraft altitude
250.0 km (155.4 miles)

Original image scale range
50.3 cm/pixel (with 2 x 2 binning) so objects ~151 cm across are resolved

Map projected scale
50 cm/pixel and North is up

Map projection
Equirectangular

Emission angle
4.6°

Phase angle
90.2°

Solar incidence angle
87°, with the Sun about 3° above the horizon

Solar longitude
86.8°, Northern Spring

For non-map projected images
North azimuth:  96°
Sub-solar azimuth:  51.2°
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   (306MB)

IRB color
map-projected   (209MB)

JP2 EXTRAS
Black and white
map-projected  (150MB)
non-map           (150MB)

IRB color
map projected  (68MB)
non-map           (191MB)

Merged IRB
map projected  (303MB)

Merged RGB
map-projected  (314MB)

RGB color
non map           (216MB)
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.