Matt Damon‘s stranded astronaut in “The Martian” would still have been screwed despite the just-discovered presence of water on the red planet.

“You wouldn’t want to use as it as drinking water,” Leslie Tamppari, MRO Deputy Project Scientist at NASA’s Jet Propulsion Laboratory, told TheWrap. “The water is full of perchlorates that are actually toxic to humans.”

Perchlorate is a salt that helps keep the water in a liquid state in the planet’s very low temperatures. “I suppose for an astronaut if this was their only source of water, they could maybe scoop it up and with some process that I don’t know, break it up and extract the water source,” Tamppari said. “They would have to get the salts out — just like you don’t want to drink ocean water.”

 

On Monday, just days before the release of Ridley Scott‘s film, which stars Damon as an astronaut who must fend for himself on Mars after being accidentally left behind, NASA reported the discovery of flowing water on the planet.

In terms of movie publicity, the timing of the announcement was uncanny. “It’s a nice bit of serendipity,” Fox spokesman Chris Petrikin told TheWrap.

The discovery came too late for the filmmakers. On Monday, director Ridley Scott told the New York Times that had he known about water on Mars before production began, he would have changed the storyline with Damon’s character, Mark Watney, making his own water and producing crops.

“He’d’ve found the edge of a glacier, definitely,” Scott told the Times. “But then I would’ve lost a great sequence.”

 

But according to Tamppari, Damon’s character would have faced an added challenge of removing enough of the salt to make the water drinkable.

“I guess in principle, a human could extract the water from there,” said Tamppari, who read Andy Weir’s novel on which the film is based. “Watney certainly has nifty processes that he invented along the way or made use of to help himself, so maybe he would be clever enough to do this.”

On Monday, NASA confirmed that liquid water flows on the surface of Mars, which increases the possibility that life could sustain itself on the planet.

 

NASA also found hydrated magnesium perchlorates and sodium perchlorates on the planet, producing a salty brine instead of pure water, Tamppari said.

Since the average temperature on Mars is -67° F, the perchlorates lower the freezing point of the water and allow it to exist in liquid form. “It’s just like when you salt the roads for melting the ice so cars can drive better,” she said.

While scientists had known before this week that water existed on Mars, they had thought it existed only in the atmosphere in vapor form or in the north polar regions where it would be virtually impossible for human spacecraft to land.

 

Tamppari also gave full credit to the general authenticity of Weir’s book which is filled to the brim with other scientific references.

“There are some things that [Weir] takes literary license with,” she said. “You have to make a good story, but I think compared to some science fiction, he has done a really good job with making it as realistic as possible so we applaud him for that.”

“The Martian” hits theaters on Friday.

 

Read original story Matt Damon’s Astronaut in ‘The Martian’ Couldn’t Survive Despite Water on Mars, NASA Says At TheWrap