Nasa's Mars rover Opportunity has found slivers of a bright material that looks very much like it is gypsum (calcium sulphate).
If confirmed, it would be the most unambiguous signal of water activity yet found on Mars by this mission, which manages to keep on rolling.
Creaking and arthritic it may be, but after nearly eight years, the rover is still delivering remarkable science.
Lead scientist Steve Squyres? said the find was "so cool".
Waaay cool! To read more, click here.