The UA Lunar and Planetary Lab has released a particularly beautiful new batch of HiRISE photos of the Martian surface this week. See them here.
Don't forget: The LPL is having a picnic on Mount Lemmon on Saturday, May 22. Details on how to make your reservations before the May 14 deadline here.
HiRISE team member Ken Herkenhoff tells us about the photograph:
Like Earth, Mars has seasonal polar caps that grow in the winter and retreat in the spring, but on Mars the seasonal caps are composed primarily of carbon dioxide (dry ice). Carbon dioxide is the major component of the Martian atmosphere, and a significant fraction
of the mass of the atmosphere is cycled through the seasonal caps every year.
This image shows sand dunes that are mostly covered by seasonal frost/ice in the northern spring. When the springtime sun shines on the ice, some of it penetrates to the base of the ice and warms the dark sand dune surface below. The warm sand evaporates the carbon dioxide ice from below, building gas pressure that apparently breaks the ice and carries sand to the surface as the pressure is released. The sand then cascades down the surface of the ice, forming the streaks seen in this image.