While the general public has long thought of the Red Planet as dusty and dry, and even virtually without water, it turns out that is not the case. At a NASA press conference on Monday, the space agency announced that not only were there flowing rivers and even oceans on Mars many millennia ago, even today water can be found in some areas in appreciable quantities trapped in the Martian soil.
Astronomers and exo-planet researchers note this means there is still a chance, albeit a small one, there is some form of life on Mars.
“This is tremendously exciting,” James L. Green, the director of NASA’s planetary science division, said at a press conference Monday afternoon. “We haven’t been able to answer the question, ‘Does life exist beyond Earth?’ But following the water is a critical element of that. We now have, I think, great opportunities in the right locations on Mars to thoroughly investigate that.”
The excited tone of the NASA presser marks a clear a shift for NASA, where officials have in the past played down any idea that the dusty landscape of Mars could support life.
Liquid water on Mars today
In a planetary science research published this week in Nature Geoscience, geologists definitely identified molecules that can only occur with liquid water. The team identified chemical salts known as perchlorates on the surface of the Red Planet by analyzing images taken from orbit.
“That’s a direct detection of water in the form of hydration of salts,” explained Alfred S. McEwen, a member of the faculty in planetary geology at the University of Arizona, and the principal investigator of study of images from a high-resolution camera on NASA’s Mars Reconnaissance Orbiter. “There pretty much has to have been liquid water recently present to produce the hydrated salt.”
When he says “recently,” McEwen commented he meant “days, something of that order.”
Planetary scientists have long known that a good bit of water remains on Mars, but it was thought to almost all be frozen solid in the polar ice caps. A few tantalizing hints of water elsewhere on Mars have surfaced over the years, but no definitive proof until now.
That said, the modern moisture on Mars is quite modest, likely just small patches of damp soil in a few sheltered locations, and probably not much moving water or pools of standing water.
Where the water is coming from is not obvious. While it seems unlikely, it could be that the lower part of the Martian atmosphere is more humid than expected.
“We have very poor measurements of relative humidity near the surface,” McEwen noted.
Another, perhaps more likely, possibility is underground aquifers that are frozen during the winter, but melt in the summer allowing water to seep to the surface of Mars.
Brian Murphy, a professor of physics at Butler University, notes that finding out what happened to the water on Mars could offer clues to the Earth’s distant future. “There are two fates the earth could have in store for it over billions of years – either Venus or Mars. We could either see a runaway greenhouse effect (Venus), whereas Mars went into a deep freeze for some reason.”
Finding water means possibility of life on Mars
Obviously, liquid water is one of the essential ingredients for life anywhere (at least life as we know it), and the confirmation of its presence once again raises the question of life on Mars. Opinions about whether this confirmation of liquid water on Mars means life on the dry planet vary dramatically.
Christopher P. McKay, an astrobiologist at NASA’s Ames Research Center in Mountain View, Calif., argues that the recurring slope lineae are not really a promising place to look for life on Mars. In order for water to remain liquid in these conditions, it must be so salty that nothing could survive, he noted. “The short answer for habitability is it means nothing,” he continued.
He highlighted Don Juan Pond in the Antarctic, which remains liquid year round even in temperatures below zero due to high concentrations of calcium chloride salt, as an example. “You fly over it, and it looks like a beautiful swimming pool,” McKay said. “But the water has got nothing [alive in it].”
David E. Stillman, a scientist at the Southwest Research Institute’s space studies department in Boulder, Colo., doesn’t agree. He noted the water for the perchlorate streaks might be different in various areas. Maybe they only form only during the warmest times, creating the possibility that those waters might not be too salty for bacterial life.
“If it was too salty, they would be flowing year round,” Stillman explained. “We might be in that Goldilocks zone.”