A Huge Lake Of Liquid Water Has Been Found On Mars

An ESA spacecraft detected a signal of water at the south pole. ESA/INAF/Davide Coero Bora

For decades we have searched for water on Mars, and we’ve found very little, either in the form of trickles on the surface or frozen as ice. But an incredible new discovery may change everything.

Reported in the journal Science, researchers led by Dr Roberto Orosei from the National Institute of Astrophysics (INAF) in Rome say they have found a vast reservoir of water beneath the south pole of Mars. So vast, in fact, that it looks similar to a subglacial lake on Earth – one where life could arise.

“This is potentially the first habitat we know of on Mars,” Dr Orosei told IFLScience. “It’s the first place where microorganisms like those that exist today on Earth could survive.”

The large reservoir of water was found by a radar instrument, the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument, on board ESA’s Mars Express spacecraft. The team used data collected by the spacecraft from May 2012 to December 2015.

The data showed that 1.5 kilometers (0.9 miles) below the surface, in a region called Planum Australe, there was a source of liquid water spanning about 20 kilometers (12 miles) across. The team do not know how deep this reservoir of water is, but note it is at least deeper than a few tens of centimeters, and possibly more.

It was detected by sending 29 sets of radar pulses under the surface, with reflections showing a radar signal almost identical to that from lakes of liquid water found beneath the ice of Antarctica and Greenland on Earth, heavily suggesting it is liquid water. However, the exact nature of the water at the moment is unclear.

The lake was discovered using radar pulses from the Mars Express spacecraft. USGS/ASU/ESA/INAF/Davide Coero Borga

“It’s very difficult to say what we’re really looking at,” Dr Anja Diez from the Norwegian Polar Institute in Tromsø, Norway, who wrote an accompanying perspective on the research, told IFLScience. “It could either be a thin layer of water, a large layer, or water in sediments.”

The team said they considered some other possibilities for the signal, including a layer of carbon dioxide ice or very low-temperature water ice. They suggest these are unlikely, however, because they would not have caused as a strong a reflection as seen in the data.

The characteristics of this suspected water are complicated by the conditions it is in. On Earth, subglacial lakes reach temperatures of about -60°C (-76°F). But the intense pressure of the ice above lowers the melting point of the water, to the point where it exists as a liquid in large freshwater lakes.

Under this region on Mars, however, it’s thought the temperatures drop to about -68°C (-90°F). In order for the water to remain liquid here, it is likely full of salts like magnesium, calcium, and sodium and thus briny, rather than like the freshwater lakes found under ice on Earth. We do have some briny lakes on Earth, though.

“Underneath the Antarctic ice sheet, water can be at its melting point because of the ice above,” said Dr Diez. “On Mars it’s a bit different, as really cold temperatures are expected under the ice. Water can only exist because it’s briny.”

The radar signal detected by the spacecraft. The water is shown in blue. ESA/INAF/Davide Coero Bora

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