The uncertainty of science: A re-analysis of the ground-penetrating radar data that suggested there was a liquid water lake under the Martian south pole has found that it might not be liquid water at all, but either “clays, metal-bearing minerals, or saline ice.”
The abstract can be read here.
The radar data, obtained by the European orbiter Mars Express, definitely shows a layer of bright reflection suggesting a layer of something different below the icecap. The research team decided to find out if other things besides liquid water could cause the difference.
They were able to determine what level of electric conductivity the material below the ice would need to have to match the observed signal from MARSIS. Then, they identified materials that are both conductive and present on Mars including clays, metal-bearing minerals and saline ice. “Salty ice or conductive minerals at the base of the ice sheet are less flashy, but are more in line with the extremely cold temperatures at Mars’ poles,” Bierson said.
While not explicitly excluding a liquid brine, the results open new potential explanations for the observed strong radar reflections, some of which do not require liquid brine beneath the Martian south polar ice cap.
Nothing is proven, one way or another. This research has simply underlined the uncertainty of the liquid water claim. We simply do not know what caused the bright radar reflection. All we know for certainty is that it is there.
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