If liquid water does exist under the polar ice cap south of Mars, it must be due to volcanic activity, a new study suggests.
The researchers behind the new work argued that there must be an underground heat source to melt the ice under an ice floe – although they have not sought to know if this liquid water (or volcanic heat, in this case) did exist. March.
The new study follows a controversial finding published in the journal Science last July, in which an orbiter from the European Space Agency, Mars Express, stained signs of what could be a liquid mud or a liquid water lake under the polar ice. At the time, the idea was that a high concentration of salt could prevent the water from freezing despite the cold temperatures of Mars. What is strange about this discovery is that NASA's Mars Reconnaissance Orbiter saw no lake, while radar vision entering the ground of this craft should theoretically be able to spot a such characteristic.[[[[Photos: Views of the Red Planet since the Mars Express in Europe]
According to the new study, if water is actually present, a magma chamber must be formed over the past one hundred thousand years under the Martian surface in order to melt the water ; salt would not do the business. (The scientists also pointed out that if the water did not exist, the magmatic activity would also be absent.)
"Different people can evolve differently, and we are really interested in the reaction of the community," said lead author Michael Sori, a research associate at the Lunar and Planetary Laboratory at the University of Arizona. , said in a report of the American Geophysical Union (publisher of Geophysical Research Letters, the journal in which the new study was published).
If a volcanic activity occurs on Mars, scientists say that it is a strong sign that Mars is active – and a good omen to regain life on the red planet. (A new NASA mission called InSight is investigating the possibility of volcanic activity on the red planet, but has just deployed his seismometer shield and the results will be in months or years.) Life would require a source of water, a source of energy and a kind of protection against Mars bathing in radiation.
"We think that if there is a life, it will probably have to be protected from radiation in the subsoil," said Ali Bramson, another co-head of the journal and postdoctoral researcher at Lunar and Planetary Laboratory, in the same statement. . "If magmatic processes are still active today, they may have been more common in the recent past and could provide a more widespread basal melting, which could create a more favorable environment for liquid water and therefore maybe life. "
On Earth, it is common to see liquid water under ice caps, but scientists know why this happens: our planet produces enough internal heat to melt ice that rubs against the earth's crust. But Mars is much colder than Earth. it is farther from the sun and smaller than our planet, it therefore generates less internal heat. On Mars, it is unclear what phenomenon could melt its two polar ice caps, each of which is two kilometers thick.
The new study was based on the assumption that liquid water could exist under the Martian polar ice, and then model the amount of heat generated inside the planet to determine if there was enough salt at the bottom of the ice cap. glacier to melt the ice. Salt lowers the freezing point of water and has already been used in the modeling of Mars to explain that the dark streaks appearing on the crater walls came from liquid water. Some scientists say that salt has allowed salt water to flow into the crater, while others claim that the features represent dry dust flows.[[[[The South Pole of Mars Could Hide a Large Underground Lake]
In the new article, scientists have discovered that salt alone could not raise the water temperature high enough to melt ice if salt is tucked under the ice cap. So an additional heat source is needed – hence the volcanic idea. Perhaps, the newspaper suggested, the magma sank from inside Mars to the surface about 300,000 years ago. The magma did not burst, but gathered in a room just below the surface. Over the centuries, this magma chamber has progressively cooled and the evaporated heat has melted the ice at the bottom of the southern polar plate. This scenario continues.
Mars is home to many old volcanoes, including Olympus Mons, the largest volcano in the solar system. But there is there to no convincing evidence that these volcanoes are active. In fact, many scientists argue that volcanism on Mars could have stopped millions of years ago, according to the paper's statement.
Jack Holt, a global scientist at the University of Arizona, said the paper addressed one of the reasons why water could exist under the southern polar ice cap. However, Holt, who had spoken to the authors before submitting the new article for publication but did not participate in the research, added that more research was needed to refine the answer.
"I think it was a good idea to do this type of modeling and analysis, because you have to explain the water, if it's there, and so it's really an element crucial puzzle, "said Holt in his release. "The original paper [about the polar water find, in Science] just let him hang. There might be water there, but you have to explain it, and these guys have done a really good job saying what is required and that the salt is not sufficient. "
The new research is described in a document published yesterday (February 12) in the journal Geophysical Research Letters.
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