From: Planetary Science Institute
Posted: Friday, July 27, 2018
The announcement of the presence of liquid water beneath the surface of Martian poles validates research published by PSI Senior Scientist Stephen Clifford back in 1987.
A paper published in the June 25 issue of Science says that data collected, by the MARSIS orbital radar sounder on the European Space Agency’s Mars Express spacecraft, points to a lake of liquid water buried about one mile beneath the layers of ice and dust that comprise the south polar cap of Mars.
The potential existence of such subglacial reservoirs of liquid water on Mars – which could have offered a habitable haven for native life on Mars – was first discussed by Clifford in a paper entitled “Polar Basal Melting on Mars,” which was published in the Journal of Geophysical Research on August 10, 1987.
“I believe that the evidence the paper’s authors have presented for the presence of liquid water at the base of the south polar layered deposits, at this location, is highly persuasive. It’s a finding that should be closely examined by the rest of the radar community to be sure we can rule out other alternative explanations – something I think the authors have already made an excellent effort at doing,” Clifford said.
Whatever the extent of polar basal melting now on Mars, it was almost certainly greater in the past, Clifford said. Geologic evidence suggests that the south polar layered deposits covered an area approximately twice as large 3 billion years ago as they do today; thus, there was much more ice to melt. The geothermal heat flux of Mars (which results from the decay of naturally occurring radioactive elements in its crust) is also thought to have been as much as two to three times higher at that time – which would have reduced the necessary thickness of polar ice for basal melting.
On Earth, microorganisms have been found in the subglacial lakes of Antarctica that have existed in isolation from the external Antarctic environment for 35 million years or more and, since many of the 400 subglacial lakes that have been identified so far appear to be hydraulically connected, it is reasonable to conclude that microbial life may exist nearly everywhere beneath the Antarctic ice, Clifford said.
The discovery of life in a subglacial lake on Mars would have enormous significance for our understanding of the prevalence of life in our Solar System. Ice-covered oceans are believed to exist on Europa, Ganymede, Enceladus, Titan, Triton, and several other bodies in the Solar System. On Earth, wherever we find liquid water, we also find life – so the discovery of geologically persistent liquid water on so many planetary bodies raises the possibility that life may be abundant throughout the Solar System.
“The work I did 30 years ago was basically a theoretical exercise that considered what we then knew about the extensive network of subglacial lakes and channels that exist at the base of the Antarctic and Greenland ice sheets and examined its potential relevance to the Martian polar caps,” Clifford said. “It is certainly gratifying that the MARSIS radar team has now found evidence that demonstrates that this early theoretical work has some connection to reality.”
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