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Billions of years ago, Mars had a lot of water and even rivers and oceans. However, all that water has been lost and even today the planet loses hydrogen in space.
Some scientists have identified a water cycle that could explain how Mars has become so "dehydrated" while the Earth has managed to preserve its reserves.
Mars has a medium atmospheric layer, like the Earth, which should hold back the rise of the gas, causing it to pass to ice and return to the planet's surface.
Scientists have used computer simulations to discover a previously unknown mechanism that pierces that protective layer.
Every two Earth years, the summer hits the southern hemisphere of Mars, when water vapor rises from the atmosphere below to the upper one. From there, the winds carry most of the rare gas to the North Pole, where they sink once more, but some of it escapes into space.
The Martian orbit of the Sun is much more elliptical than ours and when it is summer in the southern hemisphere, the planet is closer to its star, which means that it is much warmer than a summer of # 39; northern hemisphere.
"When it is summer in the southern hemisphere, at certain times of the day the water vapor can rise locally with warmer air masses and reach the upper atmosphere", said Dr. Paul Hartogh of the Moscow Institute of Physics and Technology (MPS) in a statement.
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Another problem is the vast dust storms that run through the entire planet and repeatedly afflict Mars at intervals of several years. The last such storms occurred in 2007 and 2018 and were documented by space probes in orbit around Mars.
"The amount of dust that swirls in the atmosphere during such a storm facilitates the transport of water vapor in high layers of air," says Alexander Medvedev of MPS.
Dust particles can absorb sunlight and heat up, raising temperatures in the atmosphere by as much as 30 degrees.
"Our model shows with unprecedented precision the dust in the atmosphere influences the micro-physical processes involved in the transformation of ice into water vapor," explains Dmitry Shaposhnikov of MPS, first author of the new study, which was a collaboration between the Moscow Institute of Physics and Technology and the Max Planck Institute for Solar System Research (MPS) in Germany.
The research was published in Geophysical Research Letters.
"The new seasonal water cycle that has been found contributes massively to the continuing loss of water from Mars," said Paul Hartogh of MPS, summarizing the results of the new study.
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