A lake of actual water has been discovered on Mars

Doug Carpenter
July 26, 2018

"If these researchers are right, this is the first time we've found evidence of a large water body on Mars", said Cassie Stuurman, a geophysicist at the University of Texas who found signs of an enormous Martian ice deposit in 2016.

The Mars Express spacecraft discovered the body of water beneath the southern ice cap. And again, the liquid involved would be far saltier than Earth's oceans (and the salts are likely perchlorates, which aren't as common on Earth).

Among the most famous missions were Viking 1 and 2, which landed on Mars in 1975 and were tasked primarily with looking for life on Mars.

The location's radar profile resembled that of subglacial lakes found beneath Earth's Antarctic and Greenland ice sheets. "Those are not ideal conditions for life to form", Siebach said. They have also detected water ice and seen drops of condensation on spacecraft. They found that the south polar region of Mars is made of many layers of ice and dust down to a depth of about 1.5 km. The lake is very likely warmed from below by geothermal heat, while at the same time is insulated from the cold at the surface by the ice itself.

It has always been suspected that the Red Planet is not as dry and arid as it looks.

"This took us long years of data analysis and struggles to find a good method to be sure that what we were observing was unambiguously liquid water", said study co-author Enrico Flamini, chief scientist at the Italian Space Agency during the research. "With no immediate means of sampling the water, the jury remains out as to the possibility of the newly-discovered lake harbouring life".

Mars may have been a watery and temperate place in the distant past, but it's been a giant dustball for many eons. The surface is scored by old gorges, canyons, beaches, ocean basins and giant volcanoes, whose eruptions could have kept things riled up on the planet.

Today, Mars is too cold and dry, and the carbon dioxide atmosphere is too thin, to allow for liquid water at the surface. The Mars water would have to have a similar make-up to actually be liquid.

The current findings, however, "cannot say anything more", Flamini said.

A back-of-the-envelope calculation indicated several hundred million cubic metres of water, equivalent to tens of billions of litres.

Using the Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument (MARSIS), radar pulses were sent below ground to inspect 200-kilometer wide patch from May 2012 to December 2015. Taking care not to damage the rest of the spacecraft, the team in charge of MARSIS took two years to deploy the radar's 130-foot-long booms.

These reflections "provide scientists with information about what lies beneath the surface". That's because the radar works best at night and when it's within 500 miles of the planet's surface. That reflection is particularly strong at interfaces with liquid water, and shows up as a distinctively bright spot in visualizations of the data.

What they believe to be a lake sits beneath the Red Planet's south polar ice cap, and is about 20km across. "You have a lot of interfaces that could do unusual things to radar signals", said Zurek, who was not involved with the research.

To be clear, there's no sign of any actual Martian microbes swimming around, and the environment is not obviously hospitable - the water at the base of the polar cap is estimated to be minus-90 degrees F, far below the typical freezing point of water. "That's the hard part".

After decades of trying to answer the question of whether Mars has liquid water, scientists appear to have found the answer, and the implications of their discovery could be huge. "It may exceed the salt content that any terrestrial organisms that we know of can survive in", he said.

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