Scientists have found more evidence that liquid water exists beneath the ice cap at Mars’ south pole, which could mean the planet is geothermally active.
2018 has the European Mars Express Orbiter found that the surface of the ice cap covers the South Pole Mars sinks and rises, suggesting liquid water may be lurking beneath. But not all scientists were convinced at the time. Mars is extremely cold, and for subglacial water to exist in liquid form on the planet, there would need to be a source of heat, such as geothermal heat. At the time of the discovery of the Mars ExpressAs a result, some scientists thought that the strange radar signal measured by the spacecraft might be explained by something else, such as some kind of dry material beneath the ice caps.
But recently, an international team of scientists led by researchers from the University of Cambridge used a different technique to study the ice sheet-covered region known as Ultimis Scopili and concluded that the presence of liquid water is actually the most likely explanation .
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Using spacecraft laser altimeter measurements from NASA’s Mars Global Surveyor satellite to map the topography, or shape, of the ice cap’s upper surface, the researchers discovered subtle patterns of elevation changes that agreed with computer model predictions that a body of water beneath the ice cap would affect its surface.
“The combination of the new topographical evidence, the results of our computer model and the radar data makes it much more likely that at least one area of subglacial liquid water exists on Mars today,” said Neil Arnold, a professor of geography at Cambridge University in one expression (opens in new tab).
Scientists were aware that Mars has thick water ice caps at both poles Earth. But they believed that unlike our planet’s ice caps, which have water-filled channels and subglacial lakes beneath them, the Red Planet’s ice caps were frozen to their base, or bottom, due to the planet’s frigid climate. The shape of Mars Ice Caps was chosen as an independent line of evidence to confirm the radar results because scientists on Earth have observed that the shape of an overlying ice sheet is influenced by the body of water below.
This is because the water in subglacial lakes reduces the friction between an ice sheet and its subsurface, allowing the ice to flow faster under the influence of gravity. On the surface of the ice sheet, this change in velocity is reflected in a dip in its surface, followed by a rise in the ice surface further down the ice flow.
Examining the surface topography in the same area where Mars Express made its radar measurements, the team found a surface ripple 6.2 to 9.3 miles (10 to 15 kilometers) long.
This feature consisted of a depression in the ice surface followed by a corresponding raised area, both of which differed by several meters from the level of the surrounding ice cap area. That size and shape are similar to those of ripples in ice sheets over subglacial lakes on Earth, the researchers said in the statement
To test this correlation and determine whether the surface ripple of the Martian ice cap could be the result of subglacial water, the team ran simulations of ice flow fitted to specific conditions on Mars.
They added an area of reduced surface friction to their computer model of a Martian ice sheet, where water would allow ice flow 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 the observed features of the actual South Pole ice cap on Mars.
A combination of the results of this simulation, the new topographic observations of the ice cap and the 2018 radar results indicate the existence of subglacial water beneath the South Pole ice cap, with deeper implications for the Red Planet’s geology.
The team believe their results suggest that the geothermal heat needed to explain the subglacial waters may come from magmatic activity that occurred relatively recently in the subsurface of Mars.
“Mars must still be geothermally active to keep the water beneath the ice cap liquid,” Arnold added. “The quality of the data coming back from Mars, both from orbital satellites and from the landers, is such that we can use it to answer really tough questions about conditions on and even below the planet’s surface.
“It’s exciting to use these techniques to find out things about planets other than our own.”
The team’s research is published in the journal natural astronomy (opens in new tab).
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