Further evidence of the existence of water beneath the Martian south pole ice cap has been discovered by a team of researchers led by the University of Cambridge. As on Earth, the so-called Red Planet has thick ice sheets at its north and south poles, with a combined volume that is roughly equal to that of the Greenland Ice Sheet. Earth’s ice caps rest on water-filled channels and even large subglacial lakes. In contrast, the polar ice caps of Mars have long been thought to be completely frozen to their underlying layers due to the cold Martian climate.
In 2018, however, that assumption was challenged by data collected by the European Space Agency’s Mars Express satellite, which is equipped with an ice-penetrating radar system dubbed “MARSIS”.
The scans revealed an area at the base of Mars’ southern ice cap that strongly reflects radar signals and which scientists initially interpreted as an area of liquid ice.
Later studies, however, muddied the picture – showing that various types of dry material found elsewhere on Mars are also capable of producing similar reflectance signals.
Additionally, to remain liquid, the hypothetical water mass needs an additional and as yet undetected heat source, such as a higher level of geothermal heat currently expected on present-day Mars.
As a result, scientists were waiting for another source of independent evidence to confirm or refute the hypothesis that liquid water exists below the South Pole.
In their study, University of Cambridge glaciologist Professor Neil Arnold and his colleagues used a space laser altimeter to map the three-dimensional shape of the upper surface of Mars’ southern polar cap.
They found that the subtle patterns of ice topography matched those predicted by computer models of how a body of water below the ice cap would affect the overlying mass.
On Earth, subglacial lakes are known to reduce friction between ice sheets and the underlying bed, thereby altering the rate at which ice flows under gravity.
This, in turn, serves to influence the surface topography of the ice sheet, usually by creating a depression in the ice surface above the lake, followed by a raised section downstream.
In their Martian data, the team identified a six-to-nine-mile undulation of the surface of the southern ice sheet that included a several-foot-deep depression and corresponding uplift.
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Paper co-author and planetary scientist Dr Frances Butcher of the University of Sheffield said: ‘This study gives the best indication yet that there is liquid water on Mars today. today, because it means that two of the main 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 that doesn’t necessarily mean life exists on Mars.
“To be liquid at such cold temperatures, the water under the South Pole might need to be really salty, which would make it difficult for any microbial life to inhabit it.
“However, it gives hope that there were more habitable environments in the past when the climate was less unforgiving.”
Professor Arnold added: “The quality of data from Mars, orbiting satellites as well as landers, is such that we can use it to answer some really tough questions about conditions on – and even below – the surface of the planet. planet.
The techniques employed on Mars, he noted, are the same ones we use to study conditions here on Earth.
Professor Arnold concluded: “It’s exciting to use these techniques to discover things on planets other than our own.
The full results of the study have been published in the journal Nature Astronomy.