The white stuff on Mars sublimated, meaning it can’t be salt and pretty much must be ice. Congrats to the Mars Phoenix team (and whoever picked their landing site). Surely this goes down as one of the best animated GIFs for many years.
These images were acquired by NASA’s Phoenix Mars Lander’s Surface Stereo Imager on the 21st and 25th days of the mission, or Sols 20 and 24 (June 15 and 18, 2008).
These images show sublimation of ice in the trench informally called “Dodo-Goldilocks” over the course of four days. In the lower left corner, lumps disappear, similar to the process of evaporation.