Mars was volcanically active “extremely recently”

Claims for a subterranean lake imply the presence of magma, geophysicists say. Andrew Masterson reports.

Mars, showing the southern polar ice cap.

Mars, showing the southern polar ice cap.


There has to have been significant volcanic activity on Mars within recent geologic time if reports of liquid water beneath the planet’s south pole are correct, a pair of geophysicists suggest.

Writing in the journal Geophysical Research Letters, Michael Sori and Ali Bramson from the Lunar and Planetary Laboratory at the University of Arizona, US, argue that a recent claim for the presence of water deep beneath the Martian ice cap can only be valid if an assertion of causal volcanic activity is also accepted.

The water claim, based on Mars Express radar evidence, was published in the journal Science in August 2018.

Researchers led by Roberto Orosei from Italy’s Instituto Nazionale di Astrofisica said they had detected a 20-kilometre-wide liquid water lake underneath the solid ice of the Planum Australe, the Martian south pole.

The water was kept liquid, they suggested, “by dissolved salts and the pressure of the ice above”.

In the latest work, Sori and Bramson neither confirm nor dispute the claim for liquid water, but they question the explanation for its continued existence, saying “no concentration of salt is sufficient to melt ice” under the conditions existing at the Martian pole.

Instead, they say, a significant subterranean heat source would be required to bring about an ice-melt of that magnitude.

The easiest explanation for the existence such a heat, they say, is the advent of a subsurface magma chamber in the past few hundreds of thousands of years.

“Thus,” the researchers conclude, “if the liquid water interpretation of the observations is correct, magmatism on Mars may have been active extremely recently.”

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