Sandy Gas Jets Hypothesized on Mars.

What's causing seasonal dark spots on Mars? Every spring, strange dark spots appear near the Martian poles, and then vanish a few months later. These spots typically span 50 meters across and appear fan shaped. Recent observations made with THEMIS instrument onboard NASA's Mars Odyssey , currently orbiting Mars , found the spots to be as cold as the carbon dioxide (CO2) ice beneath them. Based on this evidence, a new hypothesis has been suggested where the spots are caused by explosive jets of sand-laden CO2. As a pole warms up in the spring, frozen CO2 on the surface thins, perforates, and begins to vent gaseous CO2 held underneath. Within this hypothesis , interspersed dark sand would explain the color of the spots, while the underlying frozen CO2 would explain the coolness of the spots. Pictured above , an artist depicts what it might be like to stand on Mars and witness the venting of these tremendous gas and dust jets.