Before and after images from Mars Reconnaissance Orbiter have discovered the formation of a new gully on Mars sometime between November 2010 and May 2013.

Before and after images from Mars Reconnaissance Orbiter have discovered the formation of a new gully on Mars sometime between November 2010 and May 2013.

The winding gully seems to have poured out from an existing ribbon channel in a crater in Mars’ Terra Sirenum region. The leading hypothesis on how the gully formed is that debris flowed downslope from an alcove and eroded a new channel. Though it looks water-carved, the gully is much more likely to have been formed when carbon dioxide frost accumulated on the slope and grew heavy enough to avalanche down and drag material down with it.