Buried �Lakes� on Mars May Just Be Frozen Clay

New research suggests that bright reflections detected by radar beneath Mars' south pole may not have been underground lakes, but clay deposits. Scientists have known for decades that water exists below the polar caps of Mars. Researchers using the MARSIS radar instrument on the European Space Agency's Mars Express spacecraft found evidence of a lake beneath the Red Planets south polar ice caps in 2018. In 2020, the researchers also discovered signs of a few super-salty lakes. Scientists noted that these lakes could have been remnants of water once found on the surface. According to Isaac Smith (a Toronto-based planetary scientist) and his coauthors, liquid water would need to be formed and maintained at this location on Mars. York and his team believe that radar reflections can be explained by clay minerals found in Mars' south polar region. There has been some doubt among the Mars community about the lake interpretation. But Smith said that no one had presented a plausible alternative. It's exciting to be able show that radar observations can be explained by something else and that the material is there where it should be. I love solving puzzles and Mars is full of them. Scientists focused on smectites minerals, which are clays whose chemical structure is more similar to that of volcanic rock than other clays. After interacting with water, eroded volcanic rock undergoes mild chemical changes to form smectites. They noted that these clays can store large amounts of water. Smectites are abundant on Mars and concentrated in the southern highlands. Smith stated that they are often found in the vicinity of volcanoes in Alaska and Central America on Earth. However, they can be found anywhere on Earth. The researchers chilled smectites in a laboratory to minus 45 degrees Fahrenheit (minus43 degrees Celsius), which is the same temperature as Mars. The researchers found that water-laden smectites can produce bright radar reflections, even when they are mixed with other materials. Smith and his colleagues also discovered evidence of smectites when they analyzed visible and near infrared data from Mars south pole. Smith and his colleagues suggested that smectites were formed at Mars' south pole during warm spells when water was present. These clays with water content were later submerged under water ice. Smith stated that looking backwards in history, we can see evidence of liquid water being present over a greater area than we expected. These clays are located at or below the south polar caps, so it must have been warm enough to support liquids long ago. The researchers concluded that smectites were a better explanation for the bright radar reflections observed there, rather than super-salty lake. Smith stated that science is a process and scientists are constantly seeking the truth. It doesn't mean it is wrong to publish 2018's first radar observations just because another material can do the same. This gave many people new ideas for experiments, modeling, and observations. These ideas can be applied to other Mars investigations, as they have been for me. Smith stated that in the future, he would like to do the measurements at colder temperatures with a wider range of clays. It is possible that other clays on Mars can make reflections as well, so it would be a good idea to continue the discussion. Today, July 29, the scientists presented their findings in Geophysical Review Letters. Copyright 2021 Space.com. A Future company. All rights reserved. This material cannot be broadcast, redistributed, rewritten, or published.