The Fun of Change Detection
The Fun of Change Detection
ESP_021733_1275  Science Theme: Aeolian Processes
Seeing evidence that material has recently moved on the Martian surface is an in-your-face reminder that Mars is a dynamic, changing planet, so I am always excited when I get the chance to search pairs of HiRISE monitoring images for changes that have occurred on the Martian surface.

This particular image shows dunes in the Southern Hemisphere of Mars, and when I saw that it was part of a series of monitoring images, I had to take a closer look. It turns out that HiRISE has now snapped pictures of these dunes for three Mars years in a row, to check for changes that have occurred over that time.

I compared the image from the second Mars year to the most recent one. The observations were taken with different lighting conditions, so it can be tricky to compare the images and say with certainty whether there have been measurable changes. However, this cutout shows unmistakable differences. The new image shows gullies on the dune that were clearly not present in the earlier image, which means that there was activity in this location sometime between when the two images were taken!

Written by: Anjani Polit  (20 April 2011)
Acquisition date
16 March 2011

Local Mars time

Latitude (centered)

Longitude (East)

Spacecraft altitude
251.7 km (156.4 miles)

Original image scale range
50.6 cm/pixel (with 2 x 2 binning) so objects ~152 cm across are resolved

Map projected scale
50 cm/pixel and North is up

Map projection

Emission angle

Phase angle

Solar incidence angle
46°, with the Sun about 44° above the horizon

Solar longitude
255.8°, Northern Autumn

For non-map projected images
North azimuth:  97°
Sub-solar azimuth:  24.3°
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   (227MB)

IRB color
map-projected   (117MB)

Black and white
map-projected  (111MB)
non-map           (129MB)

IRB color
map projected  (44MB)
non-map           (134MB)

Merged IRB
map projected  (208MB)

Merged RGB
map-projected  (197MB)

RGB color
non map           (133MB)
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.