British scientists say they have found evidence which “gives the best indication yet that there is liquid water on Mars”.
Their study is the first independent lead using data, apart from radar, that such water lies beneath the red planet’s south polar ice cap.
But the experts have also cautioned that it “does not necessarily mean that life exists on Mars“.
As with the situation on Earth, Mars has ice caps at both poles, which contain a combined volume of water ice similar to the Greenland Ice Sheet.
Earth’s ice sheets are underlain by water-filled channels and grand subglacial lakes.
And until now, it was believed that Mars’ sheets were frozen down to their beds because of the cold climate on the planet.
However the scientists said their evidence “makes it much more likely that at least one area of subglacial liquid water exists on Mars” and that the planet “must still be geothermally active in order to keep the water beneath the ice cap liquid”.
The international team, including experts from Cambridge University, Sheffield University, the Open University, Nantes University and University College Dublin, used spacecraft laser-altimeter measurements of the shape of the ice cap’s upper surface to identify patterns in its height.
They then showed that these patterns match computer model predictions for how water beneath the ice cap would affect the surface.
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Dr Frances Butcher, from the University of Sheffield, said: “This study gives the best indication yet that there is liquid water on Mars today because it means that two of the key pieces of evidence we would look for when searching for subglacial lakes on Earth have now been found on Mars.
“Liquid water is an essential ingredient for life, although it does not necessarily mean that life exists on Mars.”
NASA’s Perseverance rover on Mars in August 2021. Pic: NASA/JPL-Caltech
Dr Butcher added: “In order to be liquid at such cold temperatures, the water beneath the south pole might need to be really salty, which would make it difficult for any microbial life to inhabit it.
“However, it does give hope that there were more habitable environments in the past when the climate was less unforgiving.”
Professor Neil Arnold, from Cambridge’s Scott Polar Research Institute, said: “The combination of the new topographic evidence, our computer model results and the radar data make it much more likely that at least one area of subglacial liquid water exists on Mars today, and that Mars must still be geothermally active in order to keep the water beneath the ice cap liquid.”
The results were reported in the journal Nature Astronomy.