On Mars what was thought to be water, is sand after all

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It was a recent study that came to state that the already detected dark features that appear seasonally on the slopes of Mars are actually the result of sand and dust flows, not water in the subsurface of the red planet, as was believed.

These dark features on Mars that in the year 2015 made NASA claim to be the fruit of the water flow in the subsurface of the planet are ultimately the result of mixed sand and dust flows, a new study published this week in the journal Nature Geoscience.

Called RSL, as recurring slope lines, these effects caused researchers to believe that there was water flowing underground in Mars. But in fact, the flow that gives rise to these traits, has other characteristics that link to the behavior of the displacement of sand dust in dunes, not water, say the researchers responsible for the research.

The team responsible for this study, with representatives from the US Geological Survey, the Planetary Science Institute, the University of Arizona and the University of Durham, England, obtained results through observations made by the high-resolution camera of the Mars Reconnaissance Orbiter.

The RSL, already discovered in 2011, appear seasonally on the slopes of Mars (more specifically in the Ecuadorian zone, in the northern plains and in the southern latitudes), but no one knows the real reason. These traits emerge every year around the warmer time of the red planet, and they increase and darken until they disappear with the arrival of winter. This seasonality and already known time, led to believe that it was water flowing, however, scientists did not understand the reason to only appear on the steepest slopes.

The scientists responsible for the study began to analyze 10 locations where the RSL were, and in this way, they learned that the traces, regardless of the slope, ended at similar points. That is, if it were a liquid substance, the traces would vary on slopes of different lengths. The study also indicates that these behave like grains of sand in dunes, and sit at the same “angle of rest”. “It cannot be a coincidence,” said Alfred McEwen, one of the team’s investigators.

This is not to say that there is no water on Mars, it is known that the poles of Mars contain large amounts of ice, as well as the subsurface. There are also salts capable of absorbing water vapor from the atmosphere, often even forming liquid.

These same salts of hydrates were one of the reasons that led scientists to believe that water could actually be involved in the formation of RSL. They may even be, says the latest study.

That is, the presence of water vapor and the hydration of the salts can trigger the formation of RSL. However, we still do not know why traces appear on some slopes and in others not. Already liquid existence on the surface is unlikely, say the scientists strongly.

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