London:
An international team of researchers has found new evidence for the possible existence of liquid water under Mars’ Antarctic Ice Sheet.
The results, published in the journal Nature Astronomy, provide the first independent line of evidence, using data other than radar, that there is liquid water beneath Mars’ south pole.
The researchers, led by the University of Cambridge with involvement from the University of Sheffield, used spacecraft laser altimeter measurements of the shape of the ice sheet’s upper surface to identify subtle patterns in height.
They then showed that these patterns matched computer model predictions for how a body of water beneath the ice sheet would affect the surface.
This rainbow-colored map shows underground water ice on Mars. Cool colors represent less than a foot (30 centimeters) below the surface; warm colors are more than 60 centimeters deep.
Their results are consistent with previous ice-penetrating radar measurements originally interpreted to show a potential region of liquid water beneath the ice.
There has been debate over the interpretation of liquid water based on the radar data alone, with some studies suggesting that the radar signal is not due to liquid water.
“This study gives the best indication so far that there is liquid water on Mars today, because it means that two of the most important pieces of evidence we would look for when looking for subglacial lakes on Earth have now been found on Mars,” he said. Frances. Butcher, second author of the University of Sheffield study.
“Liquid water is an essential ingredient for life, although it doesn’t necessarily mean that life exists on Mars,” Butcher said.
To be liquid at such cold temperatures, the researchers noted that the water under the South Pole might have to be really salty, which would make it difficult for any microbial life to inhabit it.
It does, however, give hope that there were more habitable environments in the past when the climate was less brutal, they said.
Like Earth, Mars has thick water ice sheets at both poles, roughly equal in volume to the Greenland ice sheet.
Unlike Earth’s ice sheets, which are covered by water-filled channels and even large subglacial lakes, until recently, the polar ice caps on Mars were thought to be frozen to their bottom due to the cold climate on Mars.
In 2018, evidence from the European Space Agency’s Mars Express satellite challenged this assumption.
The satellite has an ice-penetrating radar called MARSIS, which can see through the southern ice sheet of Mars. It revealed an area at the base of the ice that strongly reflected the radar signal, which was interpreted as an area of liquid water under the ice sheet.
However, later studies suggested that other types of dry materials, found elsewhere on Mars, could produce similar reflection patterns if they exist beneath the ice sheet.
Given the cold climate conditions, liquid water under the ice sheet would require an additional source of heat, such as geothermal heat from within the planet, at levels higher than expected for present-day Mars.
“The combination of the new topographical evidence, the results of our computer models and the radar data makes it much more likely that at least one area of subglacial liquid water exists on Mars today and that Mars still needs to be geothermal to absorb the water beneath the Earth.” ice cap fluid,” said Professor Neil Arnold of the Scott Polar Research Institute in Cambridge, who led the study.
On Earth, subglacial lakes influence the shape of the overlying ice sheet – the surface topography. The water in subglacial lakes lowers the friction between the ice sheet and its bottom, affecting the speed of the ice flow under gravity.
This in turn affects the shape of the ice sheet surface above the lake, often creating a depression in the ice surface followed by a raised area that flows further down.
The team, including researchers from the University of Nantes, University College, Dublin and the Open University, used a range of techniques to examine data from NASA’s Mars Global Surveyor satellite of the surface topography of the portion of the Antarctic ice sheet of Mars where the radar signal was detected. recognized.
Their analysis revealed a surface wave of 10 to 15 kilometers consisting of a depression and a corresponding raised area, both of which are several meters away from the surrounding ice surface.
This is comparable in scale to undulations over subglacial lakes here on Earth. The team then tested whether the observed undulation on the ice surface could be explained by liquid water at the bottom.
They performed computer model simulations of ice flow, adapted to specific conditions on Mars. They then introduced a patch of reduced bed friction into the simulated ice sheet bed where water, if any, would cause the ice to slide and accelerate.
The researchers also varied the amount of geothermal heat that comes from within the planet. These experiments generated undulations on the simulated ice surface that were similar in size and shape to those the team observed on the real ice sheet surface.
The similarity between the topographic undulation produced by the model and the spacecraft’s actual observations, along with the previous ice-penetrating radar evidence, suggests a buildup of liquid water beneath Mars’ Antarctic ice sheet, the researchers said.
This magmatic activity occurred relatively recently in the Martian subsurface to allow for the enhanced geothermal heating needed to keep the water in a liquid state, she added.
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