The existence of haze in Pluto’s atmosphere was confirmed by the New Horizons space probe in July 2015. This envelope of haze appears in the form of dozens of thin bluish layers distributed from the surface up to 500 kilometers away. altitude. Today, scientists provide observational evidence for a bimodal distribution.
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[EN VIDÉO] July 14, 2015: first images of the surface of Pluto For the second anniversary of the historic flyby of Pluto by the New Horizons probe, NASA has offered a realistic and spectacular ride above the distant dwarf planet. Discover its landscapes shaped by the impacts and also its internal activity as if you were there. A breathtaking journey above an unexplored world at the edge of the Solar System.
Pluto has a thin atmosphere with a pressure on the surface of only one Pascal (100,000 times less than on Earth). It consists mainly of nitrogen molecules with ~0.5% methane. The photons solar ultraviolet dissociate the molecules of methane and trigger rich chemical reactions organic. The little ones hydrocarbons react with each other as well as with thenitrogen to form more complex organic compounds and ultimately particles solid which constitute the mist. The mist of Pluto was discovered by the New Horizons probe during its overview in 2015. It appears in the form of dozens of thin bluish layers distributed from the surface up to 500 kilometers in altitude.
It has been shown that this haze is very important for the heating and cooling of the atmosphere and the condensation from gas. These processes are highly dependent on particle size.
Pluto’s haze is revealed to have two types of particles
A team of scientists, led by a CNRS postdoctoral researcher at the Laboratoire de meteorology dynamic, reports observational evidence for a “bimodal” distribution of air haze Pluto, using observations from the diffusion obtained for different angles by the instruments on board new horizons. It is revealed that the haze from Pluto has two types of particles: small spherical particles with radii of a few tens of nanometers and micron-sized fluffy aggregates.
Formation process and distribution
This discovery provides key insights into the processes exotic formation of organic mist. Analysis of the bimodal distribution indicates a rapid change near the ~0.5 Pa pressure level, which has also been proposed to be the level of the detached haze layer on Saturn’s moon Titan even more shrouded in organic mist than Pluto. Around this pressure level, the small spheres that sediment downwards collide and stick together, and begin to form fluffy, porous aggregates. The number of aggregates increases rapidly due to their much larger cross section than that of the spheres of mass equivalent. This transition state is frozen when the haze particles reach the surface of Pluto. No other process is needed to form such a bimodal distribution.
Pluto’s bimodal haze distribution has implications for all frozen worlds and motivates new analyzes of haze observations over Titan and Triton (a moon of Neptune which also has a thin nitrogen atmosphere).
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