Monday, September 28, 2015

Water still flows on Mars – Le Figaro

A Nasa probe has found indirect evidence that saline water flows on the flanks of the reliefs of the red planet.

Mars is no longer the death and desert world once thought about since his overview by Mariner 4 in 1965, trumpeted Monday night Nasa at a major press conference. Analyses conducted by the Mars Reconnaissance Orbiter (MRO), the US space agency, just brought the first indirect evidence that water in liquid, still flowing regularly on the surface of the red planet. Flows made possible craters on sides by a high concentration of salts, which can lower the water melting temperature.

Traces of flows on Mars slopes had already been discovered in 1997, but has since realized that they were caused by dry ice and not by any liquid. The studied flows today are very different: they are smaller, do not dig the slopes on which they descend, and above all, they appear and disappear in summer in winter, showing that the phenomenon is not only active at the moment, but also sensitive to temperature variations. Which suggests the action of a liquid, rather than any other process, whether the wind or mere superficial landslides.

 Traces of xe9 & #; coulement on the slopes of crat XE8 & #; re Garni

Traces flow on the slopes of the crater Garni Photo Credits:

Since the discovery of these seasonal flows in 2011 by Alfred McEwen of the team at the University of Tucson (Arizona), on images with very high resolution MRO, most experts believed that the liquid in question had to be water, but without having no proof. And in particular, the spectrometer MRO does not detect the spectral signature of water in these regions. “The problem is that these dark flows that appear in summer on warm slopes of the craters are up to 5 meters wide, the gold CRISM spectrometer we work with has a resolution of 18 m wide, says Marion Massé , post-doctoral researcher at the Laboratory of Planetology and Geodynamics of Nantes, and one author of the study published Monday afternoon in the journal Nature Geoscience . It is therefore theoretically very difficult to say whether what we see is real or due to an artifact. My colleague Lujendra Ohja has solved this problem by observing the same point at different times, which can detect seasonal variations. “

As a dehumidifier

” It’s in this way that Martian summer, during the period of activity flows, it detects hydrated salts, perchlorates, which then disappear in winter, “says Marion Massé. Indirect evidence that very salty water, brine, flows at these locations. “It’s a very interesting observation, because the presence of salt explains how water can be liquid on Mars, where the atmospheric pressure is much too low,” says Nicolas Mangold, a specialist in Martian geology and planetary science laboratory Geodynamics of Nantes. Furthermore, the detection of perchlorate is far from absurd because these salts have already been detected directly in the soil of Mars, the Curiosity rover, but also the Phoenix lander of NASA. “

But finding water in liquid form is also arise many questions. In particular, where this water come from? The favorite hypothesis Lujendra Ohja and co-authors is to appeal to a phenomenon of decay: the salt content in soils absorb moisture from the atmosphere, as do the white pellets that are used in a dehumidifier, and begins to flow in the form of salt water when saturated.

“The priority target for future missions”

“It’s very interesting, welcomes Nicolas Thomas, spatial imaging specialist at the University of Bern (Switzerland), these areas of seasonal flows have clearly become priority targets for the next Mars missions. “

However, despite the enthusiasm of NASA suggesting that this type of moist environment could host primitive life forms, the idea seems very far-fetched. Because the salts in question contain chlorine, a potent antibacterial agent. What “clean” immediately all life attempting to emerge.


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