Mineral Deposits Suggest Flowing Water on Mars

The tireless rover Opportunity discovers one of the most promising signs yet showing that there was once water on Mars.

The Mars rover Opportunity has stumbled upon yet another discovery on the red planet: gypsum, a mineral that is almost surefire proof that there was flowing water on our planetary neighbour. For the past seven years, Opportunity has been slowly rolling over Mars' rocky terrain, collecting mineral samples and taking photos. The golf cart-sized explorer was only supposed to work for about four months on the planet, but has exceeded all expectations of its longevity. And now its gypsum discovery in a crater called Endeavor adds further evidence to claims that the planet was once warmer, wetter, and habitable. Via Digital Journal:

According to [Opportunity's chief investigator Steve] Squyres and his colleague Raymond Arvidson of Washington University, the crater Endeavor was formed about 3.5 billion years ago after a space object crashed onto the surface. The groundwater that arose from the impact transformed calcium and sulfur in the crust of the planet into gypsum. NASA's Mars Reconnaissance Orbiter has also detected gypsum on the far northern areas of the planet.

The gypsum discovery arose during Opportunity's exploration of a rock formation known as Tisdale 2 that has large traces of zinc and bromine, both of which are often deposited by warm running water. Whether there's water still flowing beneath the planet's surface is unknown, but with these discoveries, it's almost certain that the planet, at some point, boasted life-sustaining H2O.