Three years ago, NASA's New Horizons spacecraft flew past the dwarf planet Pluto and its largest moon, Charon, taking high-resolution images and gathering much information. Astronomers call this pair a double planet and argue about its origin. RIA Novosti tells what is now known about Pluto.
Until recently, there was so little data about this celestial body that it was rarely mentioned even in science fiction. Opened in 1930. Long considered the ninth planet of the solar system, the most distant from the star. One year on Pluto equals 248 Earth years. The orbit is strongly inclined and intersects with the orbit of Neptune, but so that collision is impossible. There are five moons orbiting around Pluto.
Over time, it turned out that Pluto's mass is too small to be considered a real planet. Due to its unusual orbit, it was assumed that in the past it was a satellite of Neptune. This hypothesis is now not considered. Nevertheless, since 2006, Pluto has been officially assigned the status of a dwarf planet.
Icy on top, hot inside
Pluto belongs to the Kuiper Belt, a collection of icy bodies that were thrown to the outskirts of the solar system during its formation. In July 2015, NASA's New Horizons space station reached Pluto. The device flew past the planet at a distance of 12.5 thousand kilometers. Collected information for nine days. His mission did not end there: at the beginning of 2019, the station will begin to study the Kuiper belt.
The information provided by New Horizons surprised scientists. Pluto was found to have an atmosphere - though very rarefied. There is still quite violent geological activity, although the planet is completely icy. For comparison, our Moon, located much closer to the Sun, has no atmosphere, nothing happens in its interior. Based on the data obtained, scientists have made some conclusions about the internal structure of the dwarf planet and its largest satellite, Charon.
Pluto and Charon revolve around a common center of mass outside of them. Therefore, astronomers prefer to talk about a double planet - Pluto - Charon. This pair was formed more than four billion years ago from relatively small planetesimals - the embryos of planets consisting of stones, ice, dust.
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According to the prevailing hypothesis, at an early stage, a large space body crashed into Protopluton, literally squeezing out the ammonia ocean from it and creating a gravitational anomaly in place of the crater. As a result, the protoplanet turned over and changed its orbit. Four small ice satellites were gradually formed from the formed dust cloud.
By the way, modeling the history of the Pluto - Charon pair led scientists to the idea that Proto-Earth had several satellites at an early stage. According to the main hypothesis, the impact of the meteorite knocked out enough material from Proto-Earth to form the Moon in orbit. And smaller bodies simply flew out of the gravity force and are now somewhere at a distance of no closer than 800 thousand kilometers, if, of course, they survived the formation of the solar system.
Pluto may well still hide a syrupy salty poisonous liquid, mainly from ammonia, under a multi-kilometer layer of ice.
The ocean is evidenced by vast lowlands located 2.5 kilometers below the average surface of Pluto. It is called the Sputnik plain. The gravitational anomaly and the shape of the tectonic depression indicate that under the ice there is a liquid body, which does not allow ammonia to freeze, as well as the energy of radioactive decay from the stone core. Another sign of the ocean is the radially diverging faults that cut across the plain. However, scientists emphasize that all this evidence is circumstantial.
The structure of the dwarf planet Pluto.
Restless bowels
Pluto's rocky core is shrouded in a mantle of water ice about three hundred kilometers thick, and a glacier of nitrogen, carbon monoxide and ammonia covers the planet from above.
Astronomers were amazed at the diversity of the dwarf planet's surface relief. Sputnik's plain is divided into polygonal cells by cracks a kilometer deep. There are many pits and bumps everywhere, possibly icebergs of water ice that have emerged from the mantle. The absence of pronounced impact craters indicates that the surface was formed by geological standards recently - no later than ten million years ago. All in all, Pluto has about five thousand meteorite craters.
Near the plain there are mountainous regions with five kilometers of peaks. Most likely, this is the result of cryovolcanism - when liquid ammonia, water or methane flows out of the bowels instead of hot lava. There is no such thing on Earth. Cryovolcanism is observed on satellites of other planets - Triton, Enceladus and, probably, on Titan.
The area of Tartarus Dorsae with a surface like a razor cut remains a mystery to scientists. Moreover, the sections stretch for hundreds of meters and kilometers, the depth is also kilometers.
A world of ice and methane dunes
A monstrous cold reigns on Pluto: the temperature is only 30-40 Kelvin above absolute zero, about minus 234 degrees Celsius. Slightly warmer at the North Pole, which has been facing the Sun for several decades on Earth.
Pluto's frozen surface is losing volatile components, mainly nitrogen and carbon monoxide. Probably, due to sublimation, pits and "razor cuts" were formed in the ice.
Pluto's atmosphere is extremely thin - just a slight haze. It is dominated by nitrogen molecules, methane, and a little water vapor. There is no free oxygen. So there is no need to even talk about traces of life in this frozen world.
But on the planet there are dunes, and hence the wind. This is the conclusion reached by a large international group of scientists. Studying the relief of the Sputnik plain, they saw ripples and decided to formulate the conditions under which such geological forms could form.
There are many sand dunes on Earth, they are on Mars, Venus, Titan. They need a wind capable of carrying large masses of particles, a material for the particles from which dunes are formed, and the actual place where they would anchor. It looks like all of this is on Pluto. The dunes are made from methane ice crystals.
Tatiana Pichugina