The Mystery of Martian Water, Part 2


    To be continued. Start .

    In 2005, a new modern spacecraft, Mars Reconnaissance Orbiter, entered the orbit of Mars. A HiRise high-resolution camera, a CRISM hyperspectrometer, a Sharad radar are installed on board ...

    A HiRise camera records the surface of Mars with a resolution of up to 26 cm per pixel. Such a high resolution promised to bring the exploration of the Red Planet to a new level, and the expectations of scientists were justified. A truly sensational observation was the Martian "streams", which are visible on the slopes of craters in the middle latitudes.



    For several years, scientists have been arguing about what they see, but despite all doubts, I had to admit that water leaves these traces. Liquid. At the same time, low pressure on Mars, with rare exceptions, does not allow water to be in a liquid state at zero degrees or plus temperature. The paradox was resolved with the help of salt - brine, i.e. water saturated with salts may remain liquid at minus Celsius. When spring comes, and the daytime temperature rises to -10 -5 degrees Celsius, then the brine thaws, and gradually impregnates the soil sliding down the slope, and makes it darker. Wet streaks gradually extend to the bottom of the crater, until the summer sun dries them. A similar process was observed in the deserts of Antarctica, which became an additional confirmation of the water hypothesis.

    MRO was able to examine water where it was not expected - in the middle latitudes of the northern hemisphere. Scientists have long been thinking about the cause of the significant difference in the relief of Mars - the Southern Upland is all in the mountains and craters, and the Northern Lowland is smooth.



    The most cautious researchers suggested that in the north we observe a lava sea, like the moon. Optimists timidly expressed the hope that there was an ocean in the north of Mars, which lapped the landscape, at the same time acting as a "pillow" for falling asteroids and keeping the surface from cratering. There was a lot of indirect evidence of the ocean, but, as we recall, Viking, which sat down in those places, found no signs of the sea.

    Help optimists came from the sky. Observation of the surface of Mars from the MRO satellite helped to detect fresh meteorite craters. Recent traces of meteor strikes in the northern lowlands turned out to be unusual. Something piercingly white appeared under a layer of red soil.



    And this white disappeared in the open air for several weeks.



    As far as we know, dust hides traces on Mars much more slowly - over months or years. Therefore, there was no other explanation than water ice. Excavations of Viking turned out to be not deep enough, Burrowing 20 centimeters deeper, they might have been able to get to Martian ice.



    Finally, in 2008, the Phoenix lander module landed in the north of the Red Planet at the polar latitudes. Where, according to Mars Odyssey, up to 60% of the water should be in the surface layer. Phoenix flew for water, he was prepared to search for water and he found it.



    A specially equipped bucket, more powerful than that of Viking, was able to clean off a shallow layer of dust and detect white ice. Under sunlight, the ice began to evaporate, and disappeared in a few days, but Phoenix managed to analyze both the soil and water. There were no signs of life or organics, but the question of the presence of water on Mars was closed once and for all - there is.

    But research did not stop there. Further observations from satellites revealed some regions of Mars, far from the poles, but with clear signs of glaciers. Such glaciers are observed, for example, in the east of the Hellas valley.



    It is believed that in some periods of the life of Mars, its axis shifted to 45 degrees, as a result of which, for some time, the south geographical pole shifted to Hellas . Changing the axis tilt led to serious climate change. The polar cap began to evaporate actively, and snow fell at the new pole, due to which the accumulation of glaciers began.



    But after some time, the poles of Mars returned to their places and the cataclysms calmed down. According to the existing assumption, this could happen in a relatively recent time - about 20 million years ago. When the atmosphere was already thin enough and there was no question of any seas and oceans, the warm and humid period ended one and a half to two billion years earlier.

    The Curiosity rover, landing in the crater of Gale, near the equator, did not find ice. But he first discovered river pebbles.



    And he managed to determine that in the surface soil contains from 3 to 6% of water bound at the chemical level. Moreover, the Russian DAN device made it possible to determine even the layered nature of the soil. In some areas, the upper layer was “dry” - from 3%, and the lower (within 60 cm, on which the DAN “punches”) “wet” - up to 5%. And somewhere it was the other way around - from above 5%, and in depth - 3%.

    SAM gas chromatograph showed that heating the soil to 400 degrees Celsius allows you to evaporate water and other gases useful to humans: oxygen, nitrogen, carbon dioxide. But heating above already contributes to the release of sulfur and chlorine compounds, which no longer contribute to life. In one sample, the SAM device was able to determine even 6% of the water, and nitrates and organic matter were also found there .

    Already in 2015, the results of two studies on water were published. The first was conducted from orbit using the radars of the Mars Express and MRO satellites. This time they were able to evaluate the deposits in the glaciers in the middle latitudes.



    Satellite sensing of mid-latitude glaciers showed that these water reserves will allow one meter to fill ideally smooth Mars into the hypothetical ocean. Thanks to previous radar research, it was possible to calculate that having melted the northern and southern polar caps, it is possible to fill an ideally smooth planet the size of Mars with water another 22 meters deep. Now it remains only to estimate the reserves of the northern ocean.

    The second study was conducted using the Curiosity rover. Combining the results of observations of the REMS climate station, the data on the content of chemical elements and compounds in the soil from SAM, and the readings on the concentration of hydrogen from DAN, came to interesting conclusions.



    It turned out that in autumn and spring, at night, the relative humidity of Martian air can reach 100%. And the perchlorates contained in the soil tend to absorb water from the atmosphere. Those. at some point, the salt in the soil will turn into a liquid brine, and exactly what the MRO satellite observed from space will happen - streams will flow. Curiosity does not observe this - after all, the equator is rather dry, but there should be more moisture towards the middle latitudes.

    Among other things, Curiosity observations answer the question of what is the source of seasonal “streams” observed from the satellite. It has been hypothesized that it could be permafrost or glaciers, but now it is clear that they are not required.

    Moisture arising in the night answers the question of whether microscopic life on Mars is currently possible. It turns out, possible. Not just maintaining life in a state of coma, which is possible in open space, but namely active life: reproduction, metabolism, even evolution is possible. Of course, it is unlikely that there will be local inhabitants, but then we can begin to look for or bring out terrestrial extremophiles with whom we could populate Mars, preparing it for terraforming.

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