Scientists Discover Evidence of the First Large Body of Liquid Water on Mars
A mosaic image of the region where the presumed water is. Blue represents water. Image: USGS Astrogeology Science Center, Arizona State University, INAF

Researchers have announced they may have discovered what might be a significant reservoir of liquid water below the surface of Mars. The “lake” measures 20km across and is located about 1.5km below Mars’ southern polar ice cap.

For decades Mars has teased scientists with whispers of water’s existence. Valleys and basins and streams long dried out indicate the planet’s watery past. The accumulation of condensation on surface landers as well as the discovery of substantial subterranean ice deposits propose water continues to linger in its gaseous and solid states. However liquid water has turned out to be considerably more hard-to-find. Evidence thus far implies it flows seasonally, descending steep slopes in transient trickles each Martian summer. The search for a big, enduring reservoir of wet, possibly life-giving H20 has turned up nothing. Until now.

Dark streaks on Mars’ Garni Crater known as recurring slope lineae. NASA and other scientists believe these are created by flowing salty water. Image: NASA / JPL-Caltech / Univ. of Arizona

In a paper regarding the breakthrough discovery published in the journal Science, the team of scientists in Italy reports using electromagnetic radar on the European Space Agency’s Mars Express spacecraft to probe a region around the southern pole of Mars. The radar, known as Mars Advanced Radar for Subsurface and Ionosphere Sounding, or MARSIS, echoed back more over an area of 20 km. After ruling out all other possible explanations, the researchers figured this 20 kilometer stretch must be some kind of subterranean reservoir of liquid water, at about 100 cm deep.

“I’ve run out of ideas on how to explain this in a way that isn’t water,” explains Roberto Orosei, a researcher at Italy’s National Institute for Astrophysics and lead of the team that found the formation. “We’ve tried to exhaust every possible alternative, and we think we’ve done it.”

“I can’t absolutely prove it’s water, but I sure can’t think of anything else that looks like this thing does other than liquid water,” says Richard Zurek, chief scientist for the Mars Program Office at NASA’s Jet Propulsion Laboratory, who was unaffiliated with the study. “Maybe that has to do with a shortage of imagination on my part,” he adds, “but it probably has to do with a shortage of data, too.” More radar observations, he says, could give rise to explanations scientists haven’t even thought of yet—and more questions, too.

Not that there is a shortage of unanswered questions. It is still unknown how the water stays liquid at temperatures way below 0° Celsius. The water in this specific case may be mixed with magnesium, calcium, and sodium salts, all of which are present in Martian rock, which would make it thick (and poisonous to humans)—and explain how it can exist in liquid form at temperatures around -67.7°C. But we don’t know for sure.

These discoveries still need to be confirmed—ideally by an actual trip to Mars. Then again, currently, the world’s space powers are in fact forbidden to actually get near any Martian water, per the 1967 Outer Space Treaty, out of concerns for contaminating any life which might be there with our human presence.