Thursday, June 2, 2016

Oxygen from the tchouri comet is older than our solar system – Sciences et Avenir

DISCOVER. In October 2015, a team of researchers highlighted the presence of molecular oxygen (O 2 ) in the coma of Comet 67P / Churyumov- Gerasimenko (aka “tchouri”). But one question remained: how come it is this oxygen there? Researchers offered two hypotheses: the first is that this oxygen come from the break water molecules (H 2 O) under the effect of solar radiation into several sub-compounds with oxygen famous ( O 2 ). The Herschel Space Telescope has already observed the thing on some moons of Jupiter (Europa, Ganymede and Callisto) and in the rings of Saturn. However, a hypothesis that seemed unlikely, especially because solar radiation affects only the top layer of the surface of the comet. Therefore, the amount of molecular oxygen produced by this process are minimal. However, this study reported a large amount of oxygen. The other hypothesis was this: that oxygen was present at the time of formation of the comet and was trapped in the ice at the time of the formation of tchouri. Now, in the universe, this compound is particularly rare. Certainly oxygen in the form of free atoms (O) is relatively common. It is even the third most abundant element in the universe after hydrogen (H) and helium (He). But in its molecular form (O 2 ) is another story. This molecule is was detected for the first time in the interstellar medium than in 2007!

The water in the comet tchouri remained in solid form since its formation

It seems that truth takes a bit of both . This is what has just shown a study published in The Astrophysical Journal Letters. French researchers from CNRS (Aix-Marseille University and Pierre and Marie Curie) will explain that oxygen tchouri be older than our solar system, and come from many of the interstellar medium. “ The oxygen was formed from water molecules broken by the bombing of galactic cosmic rays when they were in the form of ice grains located in the interstellar cloud that preceded the formation of the nebula protosolar “explains Olivier Mousis, researcher at the Astrophysics Laboratory of Marseille and co-author of the study. “ The oxygen molecules thus formed are stabilized at their inclusion in the holes created in the ice water by the bombing of galactic cosmic rays. These ice grains would subsequently transported to the external parts protosolar of the nebula, and would agglomerated to form comets “tells the researcher

Corollary to this discovery. tchouri since still today releases oxygen when the ice that makes up the bottom under the effect of solar radiation, this means that the water in comet remained in solid form since its formation. “ Because if the ice had melted, the oxygen would be released. However, the release of this gas in the coma of Comet is closely correlated to the melting of the ice core tchouri “says Françoise Pauzat, researcher at the laboratory of Theoretical Chemistry, and also co-author of the article. Therefore, it can be inferred that not the temperature of the ice which consists tchouri is passed above 150 ° K (water ice sublimation temperature). Even if the comet was a warm-up during the formation of the protoplanetary disk. “ It was found that the molecular oxygen trapped deep in the heart of the ice very well kept and not easily dégazait ” specifies Françoise Pauzat.

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