It is a discovery that should give food for thought to the Mars missions for years. A team of researchers, mostly French, just established that Mars had probably suffered, there are 3 to 3.5 billion years, a large tilting likely to upset both its geography and terrain. So the planet, covered today by robots Curiosity and Opportunity, would not have much to do with what it was at the time when life could have appeared. In question, a huge building called Tharsis volcanic dome, now corresponding to a large plateau 5000 kilometers in diameter, 12 km thick and … 1 billion billion tons!
When its formation, the volcano would eventually reach a critical mass so that it would have rotated the superficial layers of Mars – crust and mantle – around its nucleus, to find a new equilibrium position. In other words, if one is attached, for example, the location of the poles of the planet, they now correspond at all to the same area before the famous failover. A bit like having rotated the flesh of an apricot around its core.
Rivers strangely located
But how are researchers reached such a conclusion? By observing the distribution, in anarchic appearance of the Martian rivers that the idea has made its way into the mind of a planetary scientist Sylvain Bouley laboratory Geosciences Paris Sud, coauthor of the study about to be published in the journal Nature . “When you put them on a world map, they look to be scattered everywhere, but if you hand the card shape, they are significantly in a circular band,” says the specialist in planetary geomorphology. However, a circular band might make sense if it corresponded to certain latitudes, and therefore a climate in which the presence of liquid water in a given period. But today this is absolutely not the case, since if circular band there, it is parallel to the equator anything.
“In contrast, by adjusting the planet 20 to 25 degrees are obtained corresponding roughly rivers to the tropical south of Mars, “notes the researcher. This could have been a vague intuition. Except that in computing, theoretically, the position that would have been one of the poles of Mars if the Tharsis dome did not exist (yet), in a study published in 2010, a university researcher Arizona, Isamu Matsuyama, got exactly the same failover. And that’s not all, since this shift also offers a plausible explanation for the presence trail, north of Tharsis, reservoir circular ice, collected so far as an anomaly, but whose position perfectly corresponds to the zone where researchers are now old north pole of Mars.
a new map of Mars
from here Isamu Matsuyama been associated with the work of the team to recalculate the shape of the planet as it was before the changeover. Because the rotation of a planet on itself around a given axis, with considerable effects on morphology, its reliefs. “For example, there is still a bead having a higher altitude than the poles, in the equatorial zone of a planet,” says Sylvain Bouley. The result of such a shift inevitably arises a new face of the Red Planet, the Mars old, one where water has flowed, which was home to lakes, one where life was most likely to exist.
Mars map from which he will now have to learn to think, especially as this new topography obviously has important implications on the primitive Earth’s climate. “Currently, we have difficulty understanding how temperatures in the surface of Mars could be high enough to allow the existence of rivers and lakes, yet we observe the traces,” says planetary scientist François Forget it. But from the new Mars map and climate models of the Dynamic Meteorology Laboratory which it belongs, the researcher, co-author of the study multifaceted, has already found that precipitation occurred “quite precisely in the areas where rivers, dried up today, once had their source. ” “To say that the mystery is solved”, there is not that François Forget will not cross.
Still, the discovery of a determining event in the history of Mars is likely to up many obstacles to understanding a planet currently at the heart of attention.
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