21 juin 2017

La radioactivité et la vie extra-terrestre?

Voici une nouvelle théorie fort intrigante:

A new study published in the Astrophysical Journal Letters examines whether radioactive decay could support life on ocean worlds like Jupiter’s moon Europa.

In the icy planetary bodies around the Solar System, radiation emitted by long-lived radionuclides contained in rocky cores could break up water molecules and support hydrogen-eating microorganisms.

To address this possibility, the study’s authors modeled a natural water-cracking process called radiolysis, and applied the model to several known or suspected ocean worlds: Enceladus, Ceres, Europa, Titania, Oberon, Pluto, and Charon.

(...) Ocean water permeating the porous rock of the core could be exposed to ionizing radiation and undergo radiolysis, producing molecular hydrogen and reactive oxygen compounds.

“Microbial communities sustained by H2 have been found in extreme environments on Earth,” Bouquet said.

“These include a groundwater sample found nearly 2 miles (3.2 km) deep in a South African gold mine and at hydrothermal vents on the ocean floor.”

(...) While hydrothermal activity can produce considerable quantities of hydrogen, in porous rocks often found under seafloors, radiolysis could produce copious amounts as well.

Radiolysis may also contribute to the potential habitability of ocean worlds in another way.

In addition to molecular hydrogen, it produces oxygen compounds that can react with certain minerals in the core to create sulfates, a food source for some kinds of microorganisms.

“Radiolysis in an ocean world’s outer core could be fundamental in supporting life,” Bouquet said.

“Because mixtures of water and rock are everywhere in the outer solar system, this insight increases the odds of abundant habitable real estate out there.”

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