The mystery of the apparent underground lakes of Mars

Some strange signals captured by radar indicate the presence of cavities in the subsoil of a Martian area that would host lakes of liquid water, something that in theory is impossible in that area.

It all started in 2018, when scientists working with data from the ESA (European Space Agency) Mars Express orbiter announced a surprising discovery: signals from a radar instrument reflected off the South Pole of the Red Planet seemed to reveal a lake of water. liquid in the subsoil.

Since then, several more detections of such points have been announced.

In a new study, published in the academic journal Geophysical Research Letters, two scientists from NASA’s Jet Propulsion Laboratory (JPL) in the United States have discovered dozens of similar radar reflections in the South Pole area after analyzing one more set. extensive data from Mars Express, but many are in areas that should be too cold for water to remain liquid.

“We’re not sure if these signals are from liquid water or not, but they seem to be much more widespread than the original study found,” explains Jeffrey Plaut of JPL, one of the principal investigators of the MARSIS instrument (Mars Advanced Radar for Subsurface. and Ionospheric Sounding) of the orbiter, built jointly by the Italian Space Agency and JPL. “Either liquid water is common under the south pole of Mars or these signs indicate other things.”

Plaut and Aditya Khuller, from JPL and now at Arizona State University in the United States, currently do not have firm hypotheses about what the signals denote. The points where there are supposedly liquid water lakes span between 10 and 20 kilometers and are in a relatively small sector of the Martian South Pole.

Khuller and Plaut broadened the search for similar radar reflections, examining 44,000 measurements spread over 15 years of MARSIS data over the entire south polar region of Mars.

The new analysis revealed dozens of additional bright radar reflections in a much greater depth and area range than before. In some places, they were less than a kilometer and a half from the surface, where temperatures are estimated to be more than 60 degrees Celsius below zero – so cold that the water would freeze even if it contains salty minerals known as perchlorates, which can lower the freezing point of the water to a lower temperature.

The colored dots represent locations where ESA’s Mars Express orbiter has detected bright radar reflections on the south polar cap of Mars. These reflections seem to denote liquid underground water, something that is theoretically impossible in that region. They may be something else, but for now there are no ideas about what it can be. (Image: ESA / NASA JPL / Caltech)

In a 2019 study, the heat required to melt subsurface ice in this region was calculated, and the conclusion was that only recent subsurface volcanism could explain a presence of liquid water below the South Pole. However, there are no signs of recent volcanism at the south pole.

If they are not underground lakes, what are they then? This question is for now an enigma. (Source: NCYT from Amazings)

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