Solar System
Milan , December 11, 2014 – 11:44
The water on our planet can not be arrived at through primeval times ( above) to comets. This has been established scientists analyzing the data collected by the European probe Rosetta in orbit since last August around the comet 67 / P Churyumov-Gerasimenko in November and on which it landed (with difficulty) the lander Philae, now sleep waiting to reload solar batteries. The study, directed by Kathrin Altwegg, University of Bern, was published on December 10 Science .
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The images of Philae from the comet 67 / P
Deuterium
The researchers found that in the emitted gases from comet water molecules have a percentage triple deuterium than Earth’s oceans. Deuterium is an isotope of hydrogen: in its nucleus together with a proton is also a neutron. In practice, two deuterium atoms joined to an oxygen atom form a molecule of water a bit ‘more’ heavy ‘with respect to water normal . On our planet only 2-3 water molecules of 10 thousand are formed by deuterium. On the comet 67 / P three times more. The water deuterium is “a signature ‘precise that scientists use to try to figure out in which area of the nebula of gas and dust that gave rise to the solar system was formed the Earth, its evolution and where it came from all (or at least most) of the water there is on the planet today.
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Rosetta: the first photos of the departure of the lander Philae
The Late Heavy Bombardment
In fact, according to the theories the most reliable in the scientific community, the beginning of the formation of the Earth a little more than 4.5 billion years ago, the water could not be present due to the high temperatures. We arrived later, between 4.1 and 3.8 billion years ago during a period known as the Late Heavy Bombardment (LHB) characterized by a large number of impacts of meteorites, asteroids and comets not only on Earth but in all inner planets. But how did it get there? It was brought by comets or meteorites and asteroids? Since they are formed largely of water ice, comets were prime candidates. Comets come from two distinct areas of the Solar System: the more distant Oort Cloud (well beyond the orbit of Pluto) and the nearest Kuiper Belt just beyond the orbit of Neptune.
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Comet 67 / P: the latest images with extraordinary detail
New Study
In 2011, however, a study conducted by the infrared space telescope Herschel, found that the percentage of deuterium comet Hartley 2 (Kuiper Belt) was perfectly equal to those of Earth’s oceans. The hypothesis of the arrival of the water flow from comets closest shooting quota: the orbit of Hartley 2, in fact, not far exceeds that of Jupiter. But the new data collected by Rosetta made a clean sweep of this theory: even the comet 67 / P belongs to the Kuiper Belt, but the percentage of deuterium is too high, in fact: it is the highest ever found in the solar system.
Asteroids
Keep in field theory arrival brought water from asteroids, especially after recent studies (2012 and 2014) in which it was pointed out that the content of deuterium in the water of some types of meteorites and asteroids coincides exactly with the percentages of the Earth. Although some scientists believe it is too early to completely rule out the hypothesis of comets of the Kuiper Belt. All in all it was analyzed only two: Hartley and 67 / P. And the latter will await the results of the analysis carried out by Philae directly on the surface. In any case, is the first major scientific achievement scored by the Rosetta probe.
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Rosetta does a Selfie (and behind the comet appears)
December 11, 2014 | 11:44
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