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It’s one of the most intriguing questions in science: Could life exist on Mars today?
Now comes an answer: Yes, quite possibly.

Scientists’ confirmation that — for the first time — liquid water flows on the surface of Mars adds to speculation that life, if it ever arose there, could persist now. “This is tremendously exciting,” said James L. Green, the director of NASA’s planetary science division. “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.”

That marks a shift in tone for NASA, where officials have repeatedly played down the notion that the dusty and desolate landscape of Mars could be inhabited today. But now NASA officials are talking about sending a spacecraft in the 2020s, perhaps with experiments to directly look for life. Here’s a look at what the discovery means and what’s next for NASA’s Mars mission.

How they found a fingerprint
Scientists got their first tantalizing hint of the liquid in 2011, when a camera aboard the Mars Reconnaissance Orbiter spied mysterious dark streaks that lengthened as the planet warmed in the late spring and summer, then shrank in fall and winter. Scientists dubbed them “recurring slope lineae,” or RSL.

Geologists had a hunch that the streaks were caused by flows of water that were able to liquefy during warmer seasons. To see if their hypothesis had any merit, they examined data from an instrument aboard the Mars Reconnaissance Orbiter. The Compact Reconnaissance Imaging Spectrometer for Mars, or CRISM, can analyze chemicals on the surface by studying the telltale signature of dark bands in a sample of reflected sunlight.

The researchers focused on four spots where the RSL were widest and discovered a strong fingerprint for hydrated salts. Bethany Ehlmann, a planetary geologist at California Institute of Technology, said, “If there’s liquid water even today, that says that there was probably liquid water for all of the last 4.5 billion years, just like there was on Earth.”

Salt and the possibility of life
The atmosphere on Mars is cold and thin. That means pretty much any pure water on the surface would either freeze or evaporate, depending on the temperature. But if that water contained salts, it would be more stable in liquid form.

Scientists using observations from the Mars Reconnaissance Orbiter said they’ve found powerful evidence that briny water routinely flows on the Martian surface. This water source is so salty that it would likely be too harsh for life as we know it, scientists said. But the revelation strengthens the potential for life on our rust-hued neighbor — not just during its wetter past but also its arid present, experts said.

“It suggests that it would be possible for there to be life today on Mars,” said John Grunsfeld, associate administrator of NASA’s Science Mission Directorate.

Researchers haven’t spied the water directly. Instead, they detected hydrated salts that serve as a smoking gun for liquid water. “This is the first time we’ve found flowing water on a planet that’s not ours,” said study lead author Lujendra Ojha, a planetary scientist and Ph.D. candidate at Georgia Tech.

Mysteries and the next frontier
Where the water comes from remains a mystery, scientists said. It’s possible that the briny flows could come from melted ice, but many of these spots are too close to the equator for water to stay frozen.

Scientists may learn more when NASA’s InSight spacecraft arrives in September 2016. Its mission is to probe the temperature beneath the surface and learn more about the planet’s interior structure. That could help define how habitable the subsurface really is.

NASA’s next rover is scheduled to launch in 2020, but it will not be sterilized enough to kill microbes. That will put limits on the mission since NASA doesn’t want to contaminate Mars with microbial hitchhikers from Earth.

The findings also give hope that there may be natural resources that future astronauts — potentially in the 2030s — could mine to drink, to provide oxygen to breathe and to help create rocket fuel. “All of the scientific discoveries that we’re making … are giving us a much better view that Mars has resources that are useful to future travelers,” Grunsfeld said.

Los Angeles Times, New York Times