During the Martian winter a layer of carbon dioxide ice (dry ice) forms a seasonal cap over the polar region. In the spring–when the sun starts to warm the ice and the surface below–gas escapes from beneath the ice layer, carrying dust with it.
The dust is deposited on top of the ice in fans, with an orientation determined by the prevailing wind direction. In this region, the gas flows along radial channels, so that when it emerges we see a circular set of dust fans. These inspire the “starburst” description.
Written by: Candy Hansen (25 February 2009)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_011341_0980
Image: NASA/JPL/University of Arizona