What Is This?
What Is This?
ESP_028689_1180  Science Theme: Seasonal Processes
What are we looking at here? There are long linear ridges or elevated terrains covered by regular patterns of dark spots. Viewed at full resolution and in color we can see that the surface is covered by ripples and that some of the dark spots have bright halos around them.

Give up? These are sand dunes covered by carbon dioxide frost as seen in late winter when the carbon dioxide is starting to sublimate (change from solid to vapor). However, the way this sublimation happens is quite complex, leading to the spots, fans, streaks and so forth described in previous HiRISE image captions. We've imaged this spot 3 times in past years: ESP_020276_1180, ESP_019854_1180, and ESP_019287_1180.

The scene looks very similar in ESP_019854_1180 because that was almost exactly one Mars year ago, at the same season, but it looks different in the other two images. Sometimes such seasonal monitoring shows more differences in appearance in subsequent years at almost the exact same time of year, just as seasonal changes on Earth vary from year to year.

Written by: Alfred McEwen  (10 October 2012)
Acquisition date
08 September 2012

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
250.4 km (155.6 miles)

Original image scale range
50.1 cm/pixel (with 2 x 2 binning) so objects ~150 cm across are resolved

Map projected scale
50 cm/pixel and North is up

Map projection

Emission angle

Phase angle

Solar incidence angle
80°, with the Sun about 10° above the horizon

Solar longitude
168.5°, Northern Summer

For non-map projected images
North azimuth:  98°
Sub-solar azimuth:  36.9°
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   (176MB)

IRB color
map-projected   (101MB)

Black and white
map-projected  (65MB)
non-map           (113MB)

IRB color
map projected  (25MB)
non-map           (111MB)

Merged IRB
map projected  (188MB)

Merged RGB
map-projected  (168MB)

RGB color
non map           (99MB)
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’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.