Scientists find first persistent water source on Mars

Pablo Tucker
July 27, 2018

For decades now, we've been searching for water on Mars.

A team of scientists announced today that they had found a large body of liquid water beneath the southern ice caps of Mars.

The lake was discovered in the Planum Australe region using the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) instrument.

Today, there's little doubt that Mars once had liquid water on its surface at some point in its history.

Scientists find first persistent water source on Mars

"This subsurface anomaly on Mars has radar properties matching water, or water-rich sediments", lead study author Roberto Orosei, a principal investigator for the MARSIS experiment, said in an ESA news release.

MARSIS was created to find subsurface water by sending radar pulses that penetrate the surface and ice caps. This kind of lake stays liquid because the water mixes with salts like magnesium, calcium, and sodium to form a brine which lowers the water's freezing point.

In other words, the best Earth-based analogues for the newly discovered Martian lake are not just habitable, they are inhabited. We also have evidence that liquid water can still be found on the surface of Mars, from time to time.

Dr Brendan Burns, a microbiologist and astrobiologist from The University of New South Wales, says the find is intriguing evidence for the presence of life below the ice at the south pole on Mars.

Unlike many Mars discoveries, this particular revelation is all but definitive.

Scientists working on the European Space Agency's Mars Express mission said that a 19.3km wide underground liquid pool - not just the momentary damp spots seen in the past - had been detected by radar measurements near the Martian south pole. These showed a radar profile similar to those of subglacial lakes in Antarctica and Greenland.

For the past 12 years, a spacecraft-mounted radar called MARSIS has been sending radio waves down to Mars, which reflect back information about the make-up of the planet below. Much of that water was lost as Mars' protective atmosphere was stripped away, and tons of it are locked up in ice deposits. The blue triangle indicates an area of very high reflectivity, interpreted as being caused by the presence of a reservoir of water, about a mile below the surface. Although the team can not measure the thickness of the water layer, Orosei says it is much more than a thin film.

But it is quite likely that this body of water isn't a big lake.

The scientists who analyzed these radar echoes were careful to consider all the things that could have made the echoes they measured, including explanations that don't involve liquid water, and they were able to rule out most of those explanations. The weight of kilometres worth of ice above it could also be keeping the water in a liquid state, the researchers say.

In Lake Vostok's case, the frigid water serves as a refuge for species that probably got their start millions of years ago. In 2003, Mars and Earth were the closest in almost 60,000 years 55.7 million kilometres.

"They haven't seen the light of day for hundreds of thousands of years", he said. Now, if you were to figure out a way to dig down into this Martian lake, I don't think you would want to go for a swim.

"This is now our best, albeit slim chance of discovering life elsewhere in our Solar System until the more complex missions to Europa or Enceladus, the moons of Jupiter and Saturn we also believe have subterranean water sources". But Clifford holds out hope subsurface geothermal hotspots like those that power volcanoes and hot springs on Earth could sufficiently heat portions of the Martian underworld to allow liquid reservoirs to exist there without the need for life-sabotaging salt levels.

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