Scientists have discovered new evidence that liquid water exists under the ice cap at Mars’ south pole and it could mean the planet is geothermally active.
In 2018, the European Union Mars-Express orbiter discovered that the surface of the ice sheet covering the south pole of March dips and rises, suggesting liquid water may be lurking below. But not all scientists were convinced at the time. Mars is extremely cold, and for subglacial water to exist on the planet in liquid form, there would need to be a heat source, such as geothermal energy. At the time of the discovery of Mars Expresssome scientists therefore thought that the strange radar signal measured by the spacecraft could be explained by something else, for example some kind of dry material under the ice caps.
But recently, an international team of scientists led by researchers from the University of Cambridge investigated the region covered in ice cap, known as Ultimis Scopili, using a different technique and concluded that the presence of Liquid water is, indeed, the most likely explanation.
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Using laser altimeter measurements from NASA’s Mars Global Surveyor satellite spacecraft to map the topography, or shape, of the ice sheet’s upper surface, the researchers detected subtle patterns of differences in height that matched the computer model’s predictions of how a body of water beneath the ice cap would affect its surface.
“The combination of new topographical evidence, results from our computer model and radar data makes it much more likely that at least one area of subglacial liquid water exists on Mars today,” said Neil Arnold, professor of geography at Cambridge University. in a statement (opens in a new tab).
Scientists know that Mars has thick ice caps at both poles, just like Earth. But they believed that unlike our planet’s ice caps which have water-filled channels and subglacial lakes below, the Red Planet’s ice caps were frozen to their base or bed due to the climate. cold of the planet. The shape of martian ice caps was selected as an independent piece of evidence to confirm the radar results because on Earth, scientists have observed that the shape of an overlying ice cap is influenced by the mass of water below.
This is because the water in subglacial lakes reduces the friction between an ice cap and its bed, allowing the ice to flow faster under the influence of gravity. At the surface of the ice sheet, this change in velocity results in a trough in its surface followed by a rise in the surface of the ice further downstream of the ice flow.
Examining the surface topography of the same area where Mars Express made its radar measurements, the team found a surface undulation 6.2 to 9.3 miles long (10 to 15 kilometers).
This feature consisted of a depression in the ice surface followed by a corresponding raised area, both deviating from the level of the surrounding ice sheet by several meters. This scale and shape resemble those of the undulations of ice caps above subglacial lakes found on Earth, the researchers said in the release.
To test this correlation and determine whether the surface undulation of the Martian ice sheet could be the result of subglacial water, the team performed ice flow simulations tailored to specific conditions on Mars.
They introduced into their computer model of a Martian ice sheet an area of reduced bed friction where water would allow the flow of ice to accelerate. The researchers also adjusted the amount of geothermal heat in the simulation.
These simulations resulted in ripples in the computer-modeled ice surface that were similar in size and shape to observed features of the actual south polar ice cap on Mars.
A combination of the results of this simulation, new topographic observations of the ice sheet, and radar results from 2018 indicate the existence of subglacial water beneath the southern polar ice cap, with deeper implications for the geology of the Red Planet. .
The team believe their results indicate that the geothermal heat needed to account for subglacial water may come from magmatic activity that occurred relatively recently in Mars’ subsurface.
“Mars still needs to be geothermally active in order to keep the water under the ice sheet liquid,” 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 planet’s surface.
“It’s exciting to use these techniques to discover things on planets other than our own.”
The team’s research is published in the journal natural astronomy (opens in a new tab).
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