The cause of the release on the comet Churyumov-Gerasimenko became a landslide – N + 1

Burst on a comet that occurred on February 19

ESA / Rosetta / MPS for OSIRIS Team MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA

The spacecraft “Rosetta” accidentally recorded all the details of the release of which has occurred on the comet Churyumov-Gerasimenko. In observations were active almost all major machine tools, which allowed even to establish a possible cause of the release – the landslide. This is the detailed observation of the comet emissions ever recorded. The study is published in the journal Monthly Notices of the Royal Astronomical Society , briefly about it informs blog European Space Agency

Emissions of substances on comets -. Almost unpredictable process quickens in perihelion the orbit of a celestial body. As seen from Earth such phenomena lead to an abrupt increase in the brightness of the comet’s coma, but to observe their details can be only with the help of satellites. In particular, these emissions are fixed the “Rosetta” during a joint trip to the comet Churyumov-Gerasimenko. Astronomers speculate that the emissions occur when sunlight falls on the land, which has long been in the shadow.

Most emission activity was in the summer of 2015, when the comet was at perihelion. Scientists have for the safety of the unit took “Rosetta” on long distances (up to 400 kilometers), which reduced the detailed observations. In particular, it prevented explore particles emitted by the comet. The new emissions occurred after six months from the date of perihelion – February 19, 2016. At this time, the unit studied comet at a distance of 35 kilometers. By a lucky chance to watch the process managed at once with the help of nine instruments on board the “Rosetta».

Changes to the “Rosetta instrument readings “: brightness, the number of detected particles per minute and gas density

E. Grun et al. / MNRAS, 2016

The first signs of emission instruments recorded at 12:40 Moscow time – a wide-angle camera OSIRIS filmed jump brightness of the comet. The data is then supplemented by a camera with a narrow angle of view. Spectrograph ALICE found a sixfold increase in the brightness of the reflected ultraviolet light and infrared instrument MIRO – increase the brightness temperature of the surrounding gas on the comet 30 degrees.

The next leap “noticed” devices that analyze the gases and particles emitted by the comet. So, GIADA gathered more than 200 particles of three hours of observations, although the average rate fixation of large dust particles is 3-10 pieces per day. Scientists estimate velocity of the particles was about 24 kilometers per hour, and the average size – of 180 microns. To notice the stream of particles could also cameras “Rosetta” and instruments of orientation by the stars. The density of the gas surrounding the device increased by 1.5-2.5 times.

Light Change near the release point. Grayed out, the lighter, the later comet fragment was lit up.

E. Grun et al. / MNRAS, 2016

Landscape near the release point. The points marked earlier release point (August 2015)

E. Grun et al. / MNRAS, 2016

On to determine the exact source of emissions based on the pictures and the analysis of mission specialists data – it was slope “hill” in the field of Atum. Interestingly, approximately the same area are connected two other emission observed in August 2015. The authors note that most likely caused the incident has become a landslide, exposing domestic breed. Probably, it is connected with thermal stresses inside a comet caused by non-uniform illumination.

One of the evidence in favor of the hypothesis of a landslide – the large width of the ejection cone. According to scientists, if it was the source of the flow of material from the comet’s bowels, then he should have been much longer. It is hoped that the data collected will help to understand the nature and the characteristics of not only the February release, but earlier. As a result of these studies, scientists can better understand the internal structure of the comet.

«Rosetta» went into orbit around the comet Churyumov-Gerasimenko in August 2014. One of the tasks of the mission was to send descent “Fila” apparatus on the surface of the celestial body. However, the landing did not work fixing probe system and after a few “jumps” the unit was in the shaded area of ​​the comet. This reduced his scientific mission to 2.5 days, after which the “Fila” disconnected. Although the unit several times to re-get in touch now conditions on the comet will not allow him to work – because of the great distance from the sun dipped below the critical temperature. For details on the mission, “Fila” can be read in our material.

The orbiter “Rosetta” for two years a comet studied in detail who the celestial body and found in it, krypton, xenon, argon and oxygen, nitrogen and many other substances. It is expected that on September 30, the mission team manageable pit “Rosetta” comet with.

Vladimir Korolev