Evidence has proven that water did exist on Mars in the past. However, whether the planet could have ever supported life is still uncertain. NASA’s rover Opportunity has not found any signs of life since landing in January, but the hard evidence of past water makes future study all the more important. “In everything we know about life on Earth, there is no known example without liquid water. That’s the reason the search for water was so important at Mars,” Cornell University’s Steve Squyres, the principal science investigator for the Mars rover mission, said.

Researchers are still unsure how widespread water was or how long it was there. “One of the questions we don’t have an answer for is how the water was situated. Was it sort of little localized puddles or continuous over kilometers?” Squyres said.

He continued to say that the water may have oozed out of the ground but been covered by ice, thus being unexposed to the atmosphere. Yet recent research has determined that liquid water did flow on Mars’ surface due to etched ripples in stone discovered by Opportunity.

Evaporated Martian water left behind mineral deposits that include substances like hematite and jarosite. These indicate a wet, salty, acidic waterscape. “[Mars water] must have been very acidic to support the formation of minerals like jarosite, at least as acidic as tomato juice,” Jeff Kargel, a researcher with the U.S. Geological Survey in Flagstaff, Ariz., said. On Earth, such acidic waters exist, such as the wine-colored Rio Tinto basin in Spain. “The stuff is just teeming with life but the organisms there didn’t develop first in that environment… they evolved to inhabit it,” Squyres said of Rio Tinto water. Scientists are working to discover whether similar life could have originated in the water environment of Mars past.