«Traces of water» on Mars turned out to be a flow of sand, say scientists

© NASA / JPL/University of ArizonaУченые finally proved that the dark lines on Mars do not contain water«Traces of water» on Mars turned out to be a flow of sand, say scientists© NASA / JPL/University of Arizona

. Recently found dark streaks on the surface of Mars, regarded as the traces of flow of the thick brine, arose as a result of the flow of dry sand, and no moisture, say scientists in an article published in the journal Nature Geoscience.

«We found that these dark lines are never «flow» through gentle hillsides, and their length is very much depends on what angle were located sand particles against the surface of the planet. It seems that they are the product of a unique «waterless» process, characteristic only for Mars,» said Alfred McEwan of the University of Arizona in Tucson (USA).

In 2011, McEwan and his colleagues studied images taken by the HiRISE camera aboard the probe MRO. Some pictures of the steep slopes and the edges of the craters are dark band width of 0.5-5 meters, which appear and grow in summer and disappear in the Martian winter.

As suggested then, planetary scientists, these strips may be flows of very salty water. Such water remains liquid at summer temperatures on these slopes reaching 250 to 300 degrees Kelvin, or about minus 23 to plus 26 degrees Celsius. In September last year, after re-examination of images from MRO, planetary scientists have confirmed that these traces are indeed left with salty streams of boiling water. While scientists don’t know what is its source – the atmosphere or underground deposits of ice.

Over the past year, several groups of scientists have questioned the fact that dark lines do result from the flow of liquid water under the surface of Mars – it is possible that they result from the absorption of water from the Martian atmosphere salts on the surface of the slopes, where there are these lines.

In his new work McEwan and his colleagues have refuted their own initial findings, and found that water, in principle, not involved in the birth of similar lines, examining new data on the structure of dark lines collected using the instruments of the MRO in recent years.

Some of these shots, as told by McEwan, was received by the HiRISE camera in three dimensions, which allowed scientists for the first time to study how the size and shape of the dark lines, which may depend on the terrain. In total, NASA scientists were able to study approximately 150 dark lines that have arisen on the ten slopes of craters and hills in different parts of Mars.

These observations revealed one thing in common all have similar structures, the opening of which made the McEwan and his colleagues immediately to abandon the idea of «water» origin of dark lines.

It turned out that all these lines were present only on a fairly steep slope whose angle of inclination was 27 degrees or more. As soon as the line reached the more gently sloping areas, they immediately stopped, which should not happen if they were generated by streams of water. Both clearly shows that they are the product of the movement of the dry Martian sand and dust.

This idea, as McEwan admits, a good explanation of how such structures can be formed on Mars even in the absence of liquid water on its surface, but it does not reveal why the dark lines periodically appear and disappear on the planet’s surface during the onset of warm and cold seasons of the year.

As the scientist suggests, «trigger» their formation can indeed be associated with water and salt reserves, absorbing the moisture vapor at the onset of the Martian spring, but the first definite answer to this question can be obtained only when the Rovers or the marsonautes will begin a direct study of these dark lines.

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