The mission Rosetta of the European Space Agency (ESA) is more alive than ever, despite the fact that in September 2016 he "committed suicide", making an uncontrolled landing in his kite, 67P / Churyumov-Gerasimenko (67P / CG). Then it is no longer operative. If in early October, the probe gave us a new image of his kite, now the satellite brings us a new discovery.

One of ESA's main goals was to study plasma, so they needed to make Rosetta see a Shockbow nearby Comet 67P. However, although the researchers have looked, they have not been able to find it. In space missions, these situations can occur: you expect to find a phenomenon to study it, but you do not see it. Despite this, the mission was not considered a failure; on the contrary, the probe provided a lot of information about comets and space. However, according to a new data study, Rosetta hit the bow thruster, which was in its early stages and therefore went unnoticed at the outset, as explained by ESA in a press release.

For two years Rosetta patiently observed comet 67P "from different perspectives", points out the European agency, and although nobody noticed, it crossed the bow of the shock in several occasions. Thanks to this, the probe made "in situ measurements of this mysterious portion of space".


But what is this about the arc of shock? One of the best ways scientists have to study the plasma of the Solar System is comets. "Plasma is a hot, gaseous state of matter that includes charged particles and is in the Solar System in the form of a solar wind, a constant stream of particles that our star ejects into space," they explain from ESA. In the moment that the solar wind "passes near objects like planets or smaller bodies, first it reaches what is known like arc of impact", they point out. That is, this phenomenon "can be compared to the wave that forms around the bow of a ship while sailing in uncomfortable waters," says the European agency.

67P is not the only comment in which an arc of shock was seen. Around Halley was also able to climb. "Plasma phenomena they vary as the medium interacts with the surrounding environment and changes the size, the shape and nature of structures as shock arcs over time, "they explain.

Closer to the core than expected

Between 2014 and 2016, the Rosetta mission searched for signs of this phenomenon and "ventured more than 1,500 kilometers away from the comet's center in search of the comet's large-scale boundaries" and initially it seemed that all the effort had been useless. But in reviewing the data, they finally found it.

"We were looking for a typical arc of shock in the area where one might expect, far from the nucleus of the comet but found nothing, we came to the conclusion that Rosetta could not detect it, "explains Herbert Gunell of the Royal Institute of Space Aeronautics of Belgium and the University of UmeƄ (Sweden), one of the two scientists who led the study. "However, it seems the probe detected a bow shock, but was in its early stages. During a new analysis of the data, we found some 50 times closer to the comet's nucleus than expected in a case like 67P. He also moved in a way we did not expect, which is why we did not see him at first. "

Exist two main dates in the observation of the arc of shock by Rosetta. The first data are from March 7, 2015, 67P was twice as far from the Sun as Earth and as it was heading for the star, "the Rosetta data showed signs that a shock arc was beginning to form," point of the space agency. The following data is from February 24, 2016, when the comet was far from our star.

And now is when the researchers realized that "this limit was asymmetric and wider shock arcs than fully developed which were observed in other comets, "according to ESA.

"Rosetta has been the first phase to capture such an early stage in development of an arc of shock around a comet ", emphasizes Charlotte Goetz, of the Institute of Geophysics and Extraterrestrial Physics of Braunschweig (Germany) and co-author of the study. The formation arc detected in the 2015 data evolved to reach its complete development when the comet approached the Sun and increased its activity; however, we could not see this in the Rosetta data because, at that time, the probe was very close to 67P to detect the arc adult. When Rosetta picked it up again in 2016, the comet was moving away from the Sun, so the arc detected at that point was in the same state, although instead of being formed it was dissolving"he adds.

What is Rosetta?

The mission of ESA was sent in 2004 to Comet 67P with the intention of observing "its interior, studying the gas and the dust that surrounded it, and exploring your plasma environment"according to ESA.

To perform this work, the probe up to 11 scientific instruments (among them a set of instruments made up of five different sensors to study the plasma surrounding the comet) all to achieve a greater knowledge about the comets and also about the origin of the Solar System. Herbert, Charlotte and their teammates explored the data collected by the Rosetta Plasma Consortium and "They combined the data with a plasma model simulate the comet's interactions with the solar wind and determine the properties of the arc of shock, "concludes ESA.