Terra Sirenum

This region receives very little sunlight in Southern Winter, and the bluish areas consist of frost. At the latitude of this image, frost is most likely composed of water because the temperature is not low enough for CO2 condensation. The reddish regions are locations where frost has been removed, most likely by sublimation. The dark, unfrosted regions (for example, in the channel of the gully on the far right) represent the most recent activity in the gullies and are possibly a result of seasonal melting.