Still, the planet has appeared to retain some of that moisture.
"Our results may point to more habitable conditions on Mars that previously thought," said Mary Beth Wilhelm, one of the paper's co-authors, at the NASA press conference. She added that scientists will need to learn more about the briny water.
"It is very likely, I think, that there is life somewhere in the crust of Mars" said Alfred McEwen of the University of Arizona, who also worked on the study. He added that that life is likely microbial.
Wilhelm noted that in addition to supporting Martian life, water may be an important resource for human exploration and activity on the planet, by making it easier and less expensive to travel to the Red Planet.
Grunsfeld said Mars has other resources that may make it possible to grow plants, including nitrogen and carbon dioxide. Would-be farmers could build greenhouses on the planet that could grow plants—even food for inhabitants.
He said that today's announcement gives more reason to send astrobiologists and other scientists to answer the question of whether there is life on the planet.
"We can answer that question by sending rovers and by sending people," Grunsfeld said.