Pluto’s frozen nitrogen heart makes its atmosphere recede

Pluto has a heart-shaped frozen nitrogen patch, responsible for gusty winds that push in the opposite direction to the dwarf planet's rotation, say NASA scientists.

As the nitrogen within the heart-shaped ice region, called Tombaugh Regio, vaporizes in the north and turns to ice in the south, its movement triggers western winds.

The winds of Pluto above 2.5 miles blow westward, as opposed to the spin of the dwarf planet, in a "retro-rotation" for most of its year, which lasts about 248 Earth years.

The team used data from NASA's New Horizons spacecraft, which captured Pluto's observations in 2015, including Tombaugh Regio, which is located just north of the equator.

No planet in our Solar System has this unusual retro-rotation, and if the winds in Pluto push in a different direction, its spectacular landscape of valleys and icy mountains would look very different.

"This highlights the fact that Pluto's atmosphere and winds, even if the density of the atmosphere is very low, can affect the surface," said Tanguy Bertrand, astrophysicist and planetary scientist at NASA's Ames Research Center in California. and lead author of the study.

The findings point to the distinctions between the Earth and this dwarf planet 3.7 billion miles away from the Sun, whose status as a planet was degraded in 2006.

Nitrogen gas comprises most of Pluto's thin atmosphere, along with small amounts of carbon dioxide and methane.

During the Plutonian day, which lasts six days, nine hours and 36 minutes in the time of the Earth, a thin layer of this nitrogen is heated and becomes steam, and at night, the steam condenses and again forms ice.

Each sequence is like a "heartbeat", pumping nitrogen winds around the planet.

As the air strikes the surface, it transports heat, ice grains and mist particles to create suckers and plains of dark wind in the north and northwest regions.

The eastern "lobe" of Tombaugh Regio consists of highlands and nitrogen-rich glaciers, while its western side is a 620-mile ice sheet located in a 1.9-mile deep basin called Sputnik Planitia, which is key to this unusual rotation

"Sputnik Planitia can be as important for Pluto's climate as the ocean is for Earth's climate," Bertrand said.

"If you eliminate Sputnik Planitia, if you eliminate Pluto's heart, you will not have the same circulation."

The researchers found that a strong stream of air near the surface that moves rapidly along the western boundary of the Sputnik Plant basin was driven by atmospheric nitrogen that condenses on ice.

Pluto's atmosphere is mainly composed of nitrogen, with traces of methane and carbon monoxide, and temperatures can drop to -238 degrees Celsius. By 2030, scientists estimate that its atmosphere will freeze and condense.

The high cliffs of Sputnik Plantitia trap the cold air within the basin, where it circulates and strengthens as it passes through the western region.

The wind patterns that come from Tombaugh Regio can explain why it houses dark plains and wind streaks west of Sputnik Plantitia.

Winds can carry heat or can erode and darken ice when transporting and depositing mist particles.

The team extracted data from the New Horizons flyby in 2015 to represent Pluto's topography and its nitrogen ice sheets.

Then they simulated the nitrogen cycle with a weather forecast model to assess how the winds blew on the surface.

"Before New Horizons, everyone thought that Pluto was going to be a netball, completely flat, almost without diversity," Bertrand said.

‘But it is completely different. It has many different landscapes and we are trying to understand what is happening there. "

The legendary New Horizons interplanetary space probe was launched in 2006 and flew 7,800 miles above Pluto's surface, capturing detailed images of its surface.

The study has been published in Journal of Geophysical Research: Planets.

WHERE ARE THE NEW HORIZONS?

The spacecraft that gave us the first foreground views of Pluto now has a much smaller object in sight.

New Horizons is now able to fly past a recently discovered object less than 30 miles wide at the border of the solar system.

The close encounter with what is known as MU69 2014 would occur in 2019. It orbits about 1 billion miles (1.6 billion kilometers) beyond Pluto.

NASA and the New Horizons team chose MU69 2014 in August as the next potential New Horizons target, hence the nickname PT-1. Like Pluto, MU69 orbits around the sun in the frozen twilight zone known as the Kuiper Belt.

This illustration provided by NASA shows the New Horizons spacecraft. The probe surpassed Pluto in 2015 and heads to MU69 2014 for an attempted overflight in 2019 of the small icy world at the edge of the solar system.

It is believed that MU69 is 10 times larger and 1,000 times more massive than average comets, including the one currently being orbited by the European spacecraft Rosetta.

At the other extreme, MU69 is just 1 percent the size of Pluto and perhaps one tenth of the mass of the dwarf planet. So, the new goal is a good middle ground, according to scientists.

The spacecraft was recently approved for its extended mission, allowing it to continue its path to the deepest object in the Kuiper Belt.

New Horizons is expected to approach the old object on January 1, 2019.