Liquid water may be lurking beneath the southern polar ice cap on Mars, according to fresh evidence reported in Nature Astronomy.

Dark streaks and other surface patterns on Martian slopes hint that the unforgiving dust world may have once supported lakes and oceans billions of years ago. The loss of its atmosphere is believed to have caused that surface liquid to be stripped away, leaving Mars dry and barren. That said, scientists believe there is still water on Mars albeit locked up in icy deposits, frozen within regions that are cold and dry.

Now tantalizing data collected by past and present orbiting spacecraft suggests there may still be liquid water flowing on the Red Planet. An international team of astronomers led by the University of Cambridge studied detailed maps of the Martian southern polar ice cap produced by the laser altimeter instrument on the now-defunct NASA's Mars Global Surveyor satellite, according to a paper [1]published on Thursday.

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They found an anomaly on the surface of the ice cap, where the ice has formed a "raised bench" and a nearby "topographic depression", 10-15 kilometre-long features that suggest liquid water flowing underneath. Next, they ran a computer model simulating surface features for ice sheets with water flowing below and found it produced similar structures found in the anomaly. The team believes Mars must still be geothermically active to produce the heat required to melt the ice cap.

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Previous radar measurements from NASA's Mars Express orbiter highlighted a particular bright spot, where an area beneath a chunk of ice in the same region was more reflective. Some astronomers thought the high reflectivity was a sign there was liquid water beneath the ice cap. Others, however, believed the same signal could be produced by other effects, such as conductive ice or minerals in the crust.

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This latest study provides more evidence for liquid water beyond the initial radar results. "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," Professor Neil Arnold, first author of the paper and an associate professor at the University of Cambridge's Scott Polar Research Institute, [9]said .

Similar surface features are present on Earth. The rise and fall of ice have been spotted over subglacial lakes, and the team believes these same patterns are on Mars, too, meaning there is liquid water hiding beneath its ice caps. Although the evidence may seem promising, scientists have not found any confirmation of liquid water on the Red Planet yet.

Frances Butcher, co-author of the paper and a planetary scientist at the University of Sheffield in England, said the study narrows down the conditions Mars must have in order for water to exist that scientists can look for.

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"Liquid water is an essential ingredient for life," she said, "although it does not necessarily mean that life exists on Mars. 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." ®

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[1] https://www.nature.com/articles/s41550-022-01782-0

[2] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/science&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2Yza@PhiljNSL8tqQBpwG0AAAAJc&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0

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[5] https://www.theregister.com/2022/09/16/perseverance_sample/

[6] https://www.theregister.com/2022/01/19/nasa_curiosity_carbon/

[7] https://www.theregister.com/2022/06/22/mars_express_orbiter_upgrade/

[8] https://www.theregister.com/2021/11/18/martian_fossil_mistakes/

[9] https://www.sheffield.ac.uk/news/new-evidence-liquid-water-beneath-south-polar-ice-cap-mars

[10] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/science&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44Yza@PhiljNSL8tqQBpwG0AAAAJc&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0

[11] https://whitepapers.theregister.com/