The alleged underground lake on Mars discovered in 2018 appears to be not what scientists believed.
The liquid water detected under the ice– covered south pole of Mars is probably just a dusty mirage, and is actually volcanic rock .
This is the conclusion of a new study of the red planet led by researchers from the University of Texas, in the United States, and published in the journal ‘Geophysical Research Letters ‘.
Scientists in 2018 thought they were seeing liquid water when they saw bright radar reflections under the polar ice cap. However, the new study has found that those reflections matched those from volcanic plains found all over the surface of the Red Planet.
The researchers believe that their conclusion, namely volcanic rock buried under the ice, is a more plausible explanation for the 2018 discovery, which was already in doubt after scientists calculated the unlikely conditions necessary to keep water in a liquid state in the cold and arid south pole of Mars .
“For water to stay so close to the surface, you need both a very salty environment and a strong locally generated heat source, but that doesn’t match what we know of this region,” explains study lead author Cyril Grima, a planetary scientist at the University of Texas Institute for Geophysics (UTIG).
The south polar mirage dissolved when Grima added an imaginary global ice cap via a radar map of Mars . The imaginary ice showed what the terrain of Mars would look like when viewed through a mile of ice, allowing scientists to compare features of the entire planet with those of the polar cap.
Grima observed bright reflections, like those seen at the south pole, but scattered across all latitudes. In all that could be confirmed, they coincided with the location of the volcanic plains.
On Earth, iron-rich lava flows can leave behind similarly radar-reflecting rocks. Other possibilities are mineral deposits in dry riverbeds. In any case, Grima says, finding out what they are could answer important questions about the history of Mars .
But there is water on the planet
Although there may be no liquid water trapped under the south polar cap, there is plenty of water ice on Mars , even in the thick polar caps. In fact, the new study points to a wetter past for Mars .
Isaac Smith, a Mars geophysicist at the University of York, thinks the bright radar signatures are a kind of clay that forms when rock erodes in water . In 2021, Smith, who was not part of either study, found that terrestrial clays reflected radar brightly, much like the bright spots in the 2018 south pole study.
“I think the beauty of the Grima find is that while it shoots down the idea that there could be liquid water under the planet’s south pole today, it also gives us really precise places to go looking for evidence of ancient lakes and streambeds. rivers and test hypotheses about the broader drying of the Martian climate over billions of years,” he adds.
Grima’s map is based on three years of data from MARSIS, a radar instrument launched in 2005 aboard the European Space Agency’s Mars Express that has amassed a huge amount of information about Mars.Grima and his co-author, Jérémie Mouginot, a researcher at the Institute of Environmental Geosciences in Grenoble, France, plan to dig deeper into the data to see what else MARSIS can reveal about Mars.
For Smith, the study is a sobering lesson in the scientific process that is as relevant to Earth as it is to Mars.
“Science isn’t foolproof on the first try,” says Smith, who is an alumnus of UT Austin’s Jackson School of Geosciences. “That’s especially true in planetary science, where we look in places no one has ever been and depend of instruments that detect everything from a distance”.
Grima and Smith are now working on proposed missions to find water on Mars with radar, both as a resource for future human landing sites and to search for signs of past life. (EuropePress)