Rosetta witness to a brutal start on the comet – Le Figaro

COMPUTER GRAPHICS – Before the closest approach to the Sun, on the night of Wednesday to Thursday, Rosetta has already captured spectacular jets of gas emitted from the nucleus of the comet

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While the comet 67P Tchourioumov-Gerasimenko approached its perihelion, the closest point to the Sun, the European probe Rosetta is witnessing its growing business. With the strengthening of the solar flux strikes the irregular surface of the core, increasingly large amounts of gas and dust are ejected in space. On July 29, including Rosetta captured the most brutal start to date, visible as a high gloss jet from the ground. The probe was 186 km from the comet, but its high resolution camera has perfectly captured the moment when the jet was issued. On a first image taken at 1:06 p.m. UTC no particular activity was visible in the specific area in question, the “neck” of the comet, between the “head” and “body.” A little less than twenty minutes later, at 1:24 p.m., the rash is clearly visible. In the final image, at 1:42 p.m., the phenomenon is barely visible as a weak stream.

The scientists in charge of the OSIRIS camera finds that the speed of the jet was at least 10 meters per second (36 km / h), and perhaps much more. Usually, to see the gas jets, researchers are forced to overexpose their photos, making it completely saturated ring. But this time, “the jet was brighter than the core,” comments Carsten Güttler, member of the OSIRIS team at the Max Planck Institute in Göttingen, Germany.

Pictures taken at 18 minute intervals by Rosetta on July 29 Copyright: ESA / Rosetta / MPS for OSIRIS Team MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA

The eruption is even more interesting because it comes from a region of the southern hemisphere that just being exposed to the Sun After literally years in the shadows. This region, which has not been “disturbed” by the activity of particular interest to mission scientists. Another surprise, the gas jet of 29 July was powerful enough to push the limits of the magnetic field marked in contact with the solar wind, fast particles emitted continuously by our star. “The ROSINA instrument allowed us to see that the ejection also clearly changed the composition of the gases that surround the core,” enthuses Nicolas Altobelli, deputy scientific director of the Rosetta mission to the European Space Agency (ESA) . The sensor detects an excess of carbon dioxide, methane and hydrogen sulfide as compared to measurements made two days before, while the water vapor content remained constant. “We will monitor the evolution of the coma (gas envelope around the nucleus) with great interest,” says the French scientist.