Liquid water has been found on Mars, according to a study published earlier Thursday in the peer-reviewed journal Nature Astronomy. Mars, like Earth, has thick water ice at both poles. But while Earth’s glaciers have water under them, those on Mars were long thought to be solid.
An international research team led by the University of Cambridge reports the first independent set of evidence for the existence of liquid water under Mars’ south polar ice cap. Using spacecraft laser altimeter measurements of the shape of its upper surface, the team identified subtle patterns in the ice cap’s height. These models matched computer model predictions of how a body of water below the ice cap would affect the surface.
Neil Arnold, professor and research leader at the Scott Polar Research Institute at Cambridge, said: “The combination of new topographic evidence, the results of our computer model, and radar data makes it much more likely that there is at least one subglacial area of liquid water on Mars today, and that it is under this ice sheet. “To keep the water in a liquid state, Mars still needs to be geothermally active,” he said.
Subglacial lakes have an impact on Earth’s surface topography. In other words, they affect the shape of the ice sheet that lies above the lake. Water in subglacial lakes reduces friction between the ice sheet and its bed, which affects the velocity of the ice flow under gravity and ultimately the shape of the ice sheet surface. The water often creates a depression in the ice sheet and a corresponding raised area further down the stream.
Evidence collected in 2018 from the European Space Agency’s Mars Express satellite, which has an ice-penetrating radar called MARSIS, revealed an area at the base of the Red Planet’s southern ice sheet that reflects the radar signal. This was interpreted as having liquid water underneath.
The team studied data from NASA’s Mars Global Surveyor satellite of the surface topography, where the radar signal was identified. Their findings showed surface fluctuations similar to those that occur in subglacial lakes on Earth.
The researchers then tested whether the fluctuation was due to the presence of liquid water under the ice. To do this, they ran computer model simulations of the ice flow on Mars, adjusted it to suit specific conditions on the planet, and then manipulated the geothermal heat from inside the planet. The simulated ice surface produced fluctuations similar in shape and size to those observed on the real ice sheet surface.
Overall, this evidence suggests that there is water under Mars’ south polar ice cap, which has been kept liquid by geothermal heating, which may be in a liquid state due to recent magmatic activity in the planet’s underground.
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