17 avril 2016

Pluton


La mission New Horizon est passé tout près de Pluton il y a quelques mois et nous a permis d'apprendre beaucoup à propos de la planète naine. En fait, ce n'est pas euphémisme que d'affirmer que les scientifiques ont été médusé.

Extraits de l'article du NYT:

(...) “You’d expect to see a boring cratered ball”

(...) Instead, New Horizons photographed a dazzling variety of landscapes, from soaring mountains to flat plains. Pluto is proving to be far more diverse and quite different from Triton. “The big surprise is that Pluto turned out so surprising” 

(...) Nitrogen might also flow deep enough to be warmed by the interior and then erupt back at the surface — producing what scientists are surmising might be an ice volcano.

They are studying a mountain named Wright Mons that rises two miles, spans 90 miles across and has a hole at the center. “It’s not like any feature we’ve seen anywhere else in the solar system,”

(...) The most striking feature on Charon is the 600-mile long gash, longer than the Grand Canyon. (...) the gash was probably formed early in Charon’s history when the surface cracked and material from the still-warm interior oozed out.

“Charon burst at the seams,” he said.

The four small moons of Pluto turned out to be brighter and smaller than expected and spin quickly. Their axes are also tipped sideways, a configuration that defies easy explanation.

(...) Another finding indicates that the upper atmosphere of Pluto is much colder, meaning that nitrogen escapes at a rate of about a hundredth of what had been expected.



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