Between May 2012 and December 2015, the Mars Advanced Radar for Subsurface and Ionosphere Sounding (or "MARSIS" for short) surveyed the region of Mars known as the Planum Australe, a 200-kilometer area on the planet's southern polar plain, which is composed of water ice, Carbon dioxide ice, and admixed dust.
MARSIS surveyed Mars' Planum Australe region between May 2012 and December 2015 and utilized radar pulses, sending them through the surface and the polar ice caps, ultimately measuring how the radio waves came back.
"If it does turn out that liquid water is the only explanation for the radar signal", she said, "it would be an exciting result, as the subsurface can also provide shielding from the harmful radiation of space, which would be needed if there is any life on Mars given the present lack of a thick atmosphere and magnetic field to protect the surface like we have on Earth".
The lake is about 12 miles across and may not be potable, as the researchers predict it must be extremely salty to stay liquid in the -10 and -30 Celsius temperatures.
Since 1964, the United States has launched more than 20 robotic spacecraft to the red planet at a cost of more than $20 billion in an evolving campaign to map out the red planet's surface, determine the role of water in its history and to search for signs of past habitability and the organic building blocks of life, Harwood reported. Further evaluation of the bright feature indicated an interface between the ice and a stable body of liquid water.
Orosei and colleagues used a radar instrument called MARSIS aboard the Mars Express spacecraft to make their discovery.
Liquid water is hiding beneath Mars' south pole glaciers, researchers reviewing radar data have confirmed.
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Over the last ten years, different Mars missions have found increasingly more evidence of water on Mars, including large sheets of ice under the surface and salty mud flows on the surface.
He said: "Magnesium, calcium, and sodium could be dissolved in the water to form a brine". Similarly, if the Martian lake holds life forms, they're likely to be holdovers from an ancient time when Mars was more habitable.
Together with the pressure of the overlying ice, this lowers the melting point, allowing the lake to remain liquid, as happens on Earth, according to the study. Researchers are keenly interested in such reservoirs since they are reminiscent of subglacial lakes in Antarctica, which are teeming with microbial life.
The Mars Advanced Radar for Subsurface and Ionosphere Sounding instrument, or MARSIS, was developed and built by the Italians for the Mars Express mission, which entered orbit around Mars in 2003.
Richard Zurek, the chief scientist in the Mars program office at NASA's Jet Propulsion Laboratory in Pasadena, California, said the complex, nearly chaotic structure of the ice caps could affect the radar signals in unexpected ways. The bright horizontal feature at the top represents the icy surface of Mars in this region.
"This took us long years of data analysis and struggles to find a good method to be sure that what we were observing was unambiguously liquid water", said study co-author Enrico Flamini, chief scientist at the Italian Space Agency.
Authors of the Science paper, "Radar Evidence of Subglacial Liquid Water on Mars", include Orosei, Flamini and Cicchetti, plus S.E. Lauro, E. Pettinelli, M. Coradini, B. Cosciotti, F. Di Paolo, E. Mattei, M. Pajola, F. Soldovieri, M. Cartacci, F. Cassenti, A. Frigeri, S. Giuppi, R. Martufi, A. Masdea, G. Mitri, C. Nenna, R. Noschese, M. Restano and R. Seu.