This HiRISE image is of a region east of the Hellas impact basin and south of Reull Vallis. Unexpectedly, HiRISE caught a dust devil blowing across the Martian surface in the southwest portion of the image.
Dust devils form when the temperature of the atmosphere near the ground is much warmer than that above. The hot air rises, and under ideal conditions, forms a vortex that sucks in more warm air. If the vortex is strong enough, it will raise dust off the surface, forming a dust devil.
Dust devils generally form in the afternoon because the sunlight needs sufficient time to warm the surface. When this image was taken, the local time was about 3:08 p.m. In addition to the main image, we show here a small version of the HiRISE image with an arrow showing the location of the dust devil. The third subimage shows the dust devil close up .
The bright material is the dust within the vortex, and a dark shadow cast by the dust devil is visible to the right. The diameter of this dust devil is about 200 meters, but at the surface it is probably much smaller. Based on the length of the shadow in this image, the dust devil is on the order of 500 meters tall.
Written by: Nathan Bridges (24 July 2007)
This is a stereo pair with ESP_012328_1375 .
More info and image formats at http://hirise.lpl.arizona.edu/PSP_004285_1375
Image: NASA/JPL/University of Arizona