On August 6, 2014, the European Rosetta spacecraft finally reached the orbit of comet 67P / Churyumov-Gerasimenko. During this time, he often managed to very closely collide with her environment and sometimes get interesting close-up shots. But in the period when 67P is at the closest point of its orbit around the Sun, scientists of this mission begin to get a long-term perspective on how the Sun and the solar wind act on the ice interplanetary tramp.
In the course of its rotation around the Sun with a comet will begin to occur many different changes. The most obvious is the evolution of comet's tail growth. This is inevitable, since solar radiation heats the comet's ice strongly, with the formation of jets of steam and dust. But there is one nuance: the comet is built into the heliosphere of the Sun, so it also depends on the dynamics of the constant flow of the solar wind.
This process with the solar wind can be traced thanks to new research received from the Rosette team.
Everyone knows that there is ice on the surface of the comet. The mission was able to detect a certain amount of water ions in the comet's tail, which sharply increases as it approaches the Sun. Between August 2014 and March 2015, Rosetta’s special tool, a plasma consortium for analyzing the ionic composition, was able to detect a 10,000-fold increase in the velocity of solar wind ions in water. Water ions (these are H2O molecules devoid of one electron) arise in a comet's coma. This is the name of the atmosphere that surrounds the comet's core. The heat received from the Sun causes the core of the sublimation of the ice surface in the core. Coma is gradually filled with these molecules, and they are ionized by the ultraviolet light of the sun.
After going through this process in a coma, the molecules are greatly influenced by the electrical properties of sunlight. While the solar wind is becoming more intense, the comet is getting closer to the sun. At this time, the ions "feel" a great acceleration of sunlight and are simply thrown from the coma into space. Some of them also crash back into the surface of the nucleus.
In addition, these particles, originating directly from the solar wind, knocking into the core, can cause a sputtering effect. That is, explosive materials come out of the nucleus and move away into the comet's tail. These particles leave a spectroscopic imprint. So Rosetta gets this signal and can even measure it.
Using a mass spectrometer double focusing, Rosette was able to detect this atomization of atoms and discover a huge number of elements present in the ion tail of the comet. According to the information received, the elements include sodium, silicon, potassium and calcium. Interestingly, such elements can be found in carbonaceous chondrites (this is a rare class of meteorites). However, the abundance of comets exceeds meteorites, so some more work is needed to explain these differences. Scientists suggest that the speed of the comet will decrease when approaching the sun. After all, the comet will heat up, more gases will be ejected from the nucleus, and coma will increase. This can affect the deflection of solar wind particles, protecting them from colliding with the core.
Already managed to notice the deviation of protons at 45 degrees using the sensor. This is the first evidence of the interaction of the comet and the environment of the Sun.