The Pluto-Charon system has no less harmony and mutual benefit than the Earth-Moon pair! Scientists have found that Pluto's atmosphere has not evaporated into space over the past few million years only due to the existence of Charon, periodically covering Pluto from the solar wind, which carries away gas molecules.
"The atmosphere of Charon is temporary, but while it is present, Charon turns into a kind of shield that protects Pluto's atmosphere from destruction and redirects most of the flow of the solar wind away from the dwarf planet," says Carol Party of Georgia Tech at Atlanta (USA).
When the New Horizons probe arrived in the Pluto system, Alan Stern, the mission leader, and his team were surprised to find that Pluto has a complex atmosphere. It contains clouds consisting of many complex molecules, sometimes it snows, winds blow and other processes take place. It turned out that Pluto's atmosphere is more like the complex air layers of the Earth or Titan than the simple gaseous envelopes of Pluto-like planets located at a great distance from the Sun.
Another big oddity discovered by New Horizons is the way Pluto interacts with the solar wind. As scientists from NASA noted, the flow of charged particles and plasma almost does not carry gas molecules from Pluto's atmosphere into outer space, since the dwarf planet almost does not interact with it for some reason unknown to scientists.
The answer to this riddle, as Pati and her colleague John Hale discovered, is the interaction of Charon's temporal atmosphere with the solar wind.
Studying the data that New Horizons received during its flight through the Pluto system, Pati and Hale drew attention to the fact that there are large craters on the surface of Charon, during the formation of which a large amount of water and nitrogen ice, which form the basis of the "rocks" of this moon of Pluto, should was to evaporate and form a temporary atmosphere.
This atmosphere, the scientists suggested, should have influenced how the solar wind passes through the Pluto system. Hale and Party tried to figure this out by building a computer model of Charon and Pluto. This model was based on data collected from studies of Titan and Ganymede, the moons of Saturn and Jupiter, as well as observations from New Horizons.
Calculations have shown that the appearance of even a very thin temporal atmosphere on Charon will greatly affect how it interacts with the solar wind. In the presence of an atmosphere, the satellite will play the role of a kind of "breakwater" that will deflect to the sides the flow of protons emitted by the Sun and prevent them from colliding with gas molecules in Pluto's atmosphere. Thus, the strength and density of the solar wind is almost halved, which greatly slows down the "leak" of Pluto's atmosphere into space.
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On the one hand, this explains why Pluto still has an atmosphere, despite the absence of a magnetic field, and on the other, the results of calculations by scientists turned out to be about 2.5 times lower than the real values of the solar wind speed and density of its particles. made on New Horizons.
Further analysis of the data and calculations will help to find out how this discrepancy arose. They will allow calculating the density and mass of Pluto's atmosphere in the early days of its life. The original composition of Pluto's atmosphere is extremely important to scientists, as it tells what the primary matter of the solar system was made of.
As astronomers have found out, both Pluto and Charon had their own oceans of liquid water.
