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Les super-Terres pourraient nous ressembler!

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Plusieurs planètes appelées "super-Terres" ont été identifiées récemment dans notre galaxie. Il s'agit de planètes dont la taille et la masse sont supérieures à celles de notre planète, mais inférieures à celles de nos géantes gazeuses. Plusieurs se questionnent à propos de ces étranges planètes. Ressemblent-elles davantage à notre Terre ou leur surface est-elle exclusivement recouverte d'océans? Un récente étude tente de répondre à cette fascinante question:

Massive terrestrial exoplanets – planets outside our solar system – called “super-Earths,” are known to be common in our Milky Way galaxy. New research from a Northwestern University astrophysicist and a University of Chicago geophysicist suggests a super-Earth is more likely to have an Earth-like climate than has been previously thought.

The new model challenges the conventional wisdom which says super-Earths would be very unlike Earth, that each would be a waterworld, with its surface completely covered in water. The new research concludes that, instead, most super-Earths store most of their water in the mantle and thus will have both oceans and exposed continents, enabling a stable climate such as Earth’s.

(...) Water is constantly traded back and forth between the ocean and the rocky mantle because of plate tectonics, Cowan and Abbot say. The division of water between ocean and mantle is controlled by seafloor pressure, which is proportional to gravity. As the size of the super-Earths increase, gravity and seafloor pressure also go up.

The ability of super-Earths to maintain exposed continents is important for planetary climate. On planets with exposed continents, like Earth, the deep carbon cycle is mediated by surface temperatures, which produces a stabilizing feedback.

Bottom line: New research from Northwestern University and University of Chicago suggests that super-Earths -massive terrestrial planets outside our solar system – have oceans and continents and are more likely to have an Earth-like climate than has been previously thought.


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