Astronomy Picture of the Day: Radar images collected from Mars appear to show salty water bodies below the planet’s southern ice cap.

 

Water once flowed freely on the Red Planet’s surface, but it is not stable today. Discovering liquid water buried underground is essential for understanding the evolution of Mars.

Bright radar reflections from the south pole of Mars point to the existence of subglacial lakes, according to researchers in Italy. These lakes may remain liquid because of extremely high concentrations of toxic perchlorate salts.
Proving that there is liquid water on Mars would be momentous because it raises the possibility of life surviving on the planet. This was a major motivation for sending the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS), which has been orbiting onboard the Mars Express spacecraft since 2005, bombarding the surface with radar pulses and collecting the reflections.
“The MARSIS radar sounder was designed in Italy and built by a collaboration between NASA-JPL and the Italian Space Agency,” says Elena Pettinelli at Roma Tre University, who led the team analysing a region of the Mars southern ice cap, called Ultimi Scopuli. Italian research groups have vast experience in radar development, signal processing and applied electromagnetics, Pettinelli explains.
Similar radio echo sounding methods are used on Earth to search for liquid water beneath Antarctica and Greenland, although the challenges are very different.
“On Earth, we can use high resolution radar from low-flying aircrafts, so it is relatively easy to follow the shape of the bedrock below the ice and identify depressions where water might collect,” explains Pettinelli. “But MARSIS data does not allow us to define the basal topography because the spacecraft orbits at altitudes above 250 kilometres. Nevertheless, we can still use some methodologies applied on Earth to discriminate between wet and dry subglacial areas, based on the features of the reflected signal.”

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