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Billions of years ago, much of the northern Martian hemisphere would have been covered with a gigantic ocean.
NASA / GSFC
The water vapor in the Martian atmosphere continues to escape into space, prolonging the process by which planetary scientists suspect the planet of having lost the mighty ocean and the river systems that passed through it billions of years ago. years.
The current loss of water vapor, discovered by a team of researchers led by Dmitry Shaposhnikov of the Moscow Institute of Physics and Technology, took place through an unknown mechanism in the Earth's weather system.
The results are contained in an article published in the journal Geophysical Research Letters.
The lasting water loss of Mars – well documented by the Earth and probes in orbit – has long puzzled researchers.
The Martian atmosphere extends to about 160 kilometers from the surface. The middle of this gas envelope is extremely cold – cold enough to freeze rising water vapor and prevent its escape.
However, some escape from it to reach the upper layers, where the ultraviolet rays of the sun divide it into hydrogen and hydroxyl radicals, these irrevocably drifting in space.
The portion of vapor that does not reach the upper atmosphere – its trajectory halted by the cold middle layer – floats towards the North Pole of the planet, where it cools and descends to the surface.
With the help of computer analyzes, Shaposhnikov and his colleagues have now discovered how steam fulfills its Houdini role, thus revealing an entirely new water cycle.
The researchers discovered that the key was the elliptical orbit of Mars, which takes the equivalent of about two Earth years.
During the Martian summer in the southern hemisphere, the planet is about 42 million kilometers closer to the sun than during the same season in the north. This means that the southern summer is considerably warmer.
And this, suggest the researchers, opens a limited but sufficient window.
"In summer, in the southern hemisphere, water vapor can rise locally with warmer air masses and reach the upper atmosphere," says co-author Paul Hartogh of the US. Max Planck Institute for Solar Systems Research in Germany.
Indeed, the atmosphere temporarily works as a pump, making the frozen intermediate layer become permeable. The effect only occurs during the austral summer, twice a day and in very specific places.
The researchers also discovered that the huge dust storms that cover Mars every five decades or so fuel the process of loss by warming the atmosphere and accelerating the upward movement of water molecules.
"Apparently, the Martian atmosphere is more permeable to water vapor than that of the Earth," Hartogh concludes. "The new round of seasonal water that has been discovered is contributing massively to the continued water loss of Mars."
The Royal Institution of Australia has an educational resource based on this article.
You can access it here.
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