Pluto's icy heart rules its atmosphere

Pluto's icy heart rules its atmosphere
Pluto's icy heart rules its atmosphere

Scientists have found that the famous heart-shaped structure of frozen nitrogen on Pluto's surface controls the direction of the winds and the weather on this dwarf planet. The results of the study are published in the Journal of Geophysical Research: Planets.

A large bright area with a diameter of 2,300 kilometers in the shape of a heart on the surface of Pluto, called the Tombo region, became famous after the publication of photographs taken in 2015 by the interplanetary station New Horizons. New research by American and French scientists shows that Pluto's "ice heart" plays a critical role in controlling atmospheric circulation.

Pluto's thin atmosphere is made up of nitrogen gas with small amounts of carbon monoxide and methane. During the day, the solid nitrogen of the Tombaugh region evaporates, and at night the nitrogen vapor condenses and ice forms again. The authors of the study compare each such cycle with a heartbeat, and their sequence with the planet's heartbeat, which controls the movement of nitrogen flows in the atmosphere, which carry heat, moisture and ice particles. Scientists came to this conclusion after building a model of Pluto's nitrogen cycle, created on the basis of data collected by the New Horizons spacecraft.

The left (southern) half of the "heart" is a deep basin filled with nitrogen ice, the right (northern) half is a region of high mountains with nitrogen glaciers. From the right high-altitude area, nitrogen evaporates, and from the left it condenses, which creates the movement of air masses. Due to this phenomenon, at an altitude of more than four kilometers above the surface, winds blow in the westerly direction for most of the year, while the rotation of the planet occurs in the easterly direction. It is the nitrogen cycle that determines the unique retrograde rotation of the atmosphere in the direction opposite to the direction of rotation of the planet itself.

The atmospheric mass transfer model also explains the landscape zoning of Pluto's surface, in the northern and northwestern regions of which, due to the constant influx of warm humid air, the ice cover is constantly breaking down and dark flat surfaces are formed.

"This confirms the fact that Pluto's atmosphere, even if its density is very low, and winds can strike the surface," said Tanguy Bertrand, research director, astrophysicist and planetary scientist at NASA's Ames Research Center, in a press release from the American Geophysical Union. "Before the New Horizons mission, everyone thought Pluto was completely flat. But in reality, things are different. There are many different types of landscape, and we are trying to understand how they are formed."

In addition to high-altitude westerly winds, scientists have identified strong near-surface air currents in Pluto's atmosphere along the western edge of the "ice heart". At the same time, high cliffs bordering the area from the north keep these flows inside the basin, where they circulate, gaining strength.

"This region is as important to Pluto's climate as the ocean is to Earth's climate. If you remove part of the 'heart' of a dwarf planet, the movement of currents in its thin atmosphere will change dramatically," says Bertrand.

The scientist notes that the very fact of creating a model that explains the weather on a distant planet is remarkable: "Understanding how Pluto's atmosphere behaves provides us with the opportunity to compare this distant ice world with Earth, revealing both common features and differences."

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