Mars may seem dead and motionless, frozen in arid cold on its surface, but there are still a few things going on if you bother to dig. Since arriving in 2018, the InSight mission’s SEIS seismometer has detected multiple tremors, most originating in the same region, Elysium Planitia. A study published in Nature Astronomy thinks I’ve identified the source of this underground din.
“We found a huge plume below the surface of Elysium Planitiasays the main author, Adrien Broquet. This is an area where heated rocks rise and cause magma to leak out. » The French researcher from the University of Tucson, Arizona, conducted his investigation using InSight data showing that this region was abnormally agitated.
He discovered, through orbital observations, that Elysium Planitia exhibited a gravitational irregularity. Something underneath is not just a scab. He then deduced that it was a mantle plume, a set of rocks 4,000 kilometers in diameter heated somewhere between the planet’s core and its mantle.
Magmatic rise
This phenomenon, already observed on Earth, but also on Venus, occurs in localized areas: the rock is heated to such an extent that it becomes a lighter magma than the rest of the mantle and, mechanically, rises to the surface as an air bubble rises from the water. The consequences of such a mechanism, which occurs over millions of years, are clearly visible on Mars. The surface of Elysium Planitia is streaked with very deep crevasses, called Cerberus Fossae, proof that the planet has cracked under the effect of this magmatic rise. The area has a dome shape raised a few kilometers above the surrounding area.
“Between these signs, and the data from InSight and the orbiters, we had a whole bundle of clues, says Adrien Broquet. And it’s a real surprise because we didn’t expect such an activity at all. » It must be said that the geological history of Mars is, in theory, much calmer. Volcanism, very present four billion years ago, would have quickly subsided. So where does this panache come from? Mystery.
“It is possible that Mars still has heat in storenuance Nicolas Mangold, geologist at the Laboratory of Planetology and Geosciences, who did not participate in the study. Without plate tectonics, there is only a rigid surface that prevents heat from properly evacuating, so volcanic activity can continue. » Many questions remain about the origin of such a magmatic pocket and its evolution.
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