Methane ice dunes: the surface of Pluto Pluto reveals great surprises

The discovery fills a portrait of Pluto as a dynamic and changing body, one that could shed light on the mysterious objects that lie beyond its distant orbit

With just a single flyby, the New Horizons spacecraft NASA has already revealed that Pluto is a small active world with mountains and an atmosphere. Now there is another feature strikingly similar to Earth: the dunes.

The discovery, published in the journal Science, completes a portrait of Pluto as a dynamic and changing body, which could shed light on the mysterious objects that lie beyond its remoteness. orbit.

"I think this gives us better evidence than almost everything we've seen so far that this is a small, dynamic world," said lead author Matt Telfer, a planetary scientist at Plymouth University in England. "It is not a cold and icy stain in the confines of our solar system."

Pluto is so distant that it takes 248 years to orbit around the Sun; It is not less than 2.8 billion miles from our star. Before New Horizons flew by the degraded dwarf planet in 2015, little was known about this small, icy and dimly lit world.

"Prior to NASA's New Horizons mission, Pluto's surface was shrouded in mystery," Alexander Hayes of Cornell University, who was not involved in the document, wrote in a commentary. "No one knew what to expect from their surface and most scientists avoided detailed speculation, except to say that the only thing we should expect is to be surprised."

New Horizons changed all that, Telfer said. Before the mission's flyby, the best images (from the NASA Hubble Space Telescope) were blurry and pixelated. But the images of the ship revealed the varied terrain of the dwarf planet with extraordinary details.

"Suddenly we had this avalanche of data that came back in the months after the flight that revealed mountains, which revealed glaciers, that revealed a truly dynamic landscape – it's not really what was expected," Telfer said.

Pluto's giant heart-shaped nitrogen glacier was crowned as the largest glacier known in our solar system. It had an atmosphere, increasingly thin, but still nuanced and that seemed to be stuck to the dwarf planet better than scientists had predicted. Pluto could even have an ocean of ice hidden in it today.

Encouraged, Telfer began looking for more signs of geological activity on Pluto, that is, the dunes, formed when the wind moves the solid grains in regular patterns similar to those of a turtle. The dunes are found on Earth, Mars, Venus, Saturn's moon Titan (where they are made of hydrocarbons) and perhaps even Comet 67P / Churyumov-Gerasimenko. Telfer and some colleagues exchanged messages when they found promising candidates, but eventually turned out to be blots, except one.

These parallel ridges lay near high mountains and seemed to form perpendicular to the marks left by the wind "Exactly what would be expected in the formation of dunes," said Telfer.

But how could the fine atmosphere of Pluto, whose surface pressure is approximately 100,000 times smaller than that of Earth, move these grains? The scientists realized that when the sun hit the surface, raising the temperature slightly, the frozen nitrogen would sublimate: it would pbad directly from a solid state to a vapor. Those sudden puffs of nitrogen would shoot the methane grains still frozen in the air like popcorn in a microwave, allowing the wind to move these grains transported through the air.

The findings may cause researchers to reevaluate their expectations of similar activity in other worlds, Hayes said.

"If an extremely dim atmosphere like Pluto can withstand the generation of wind-driven sediment shapes, what kind of wind activity could we see in places like Io (a moon of Jupiter) or Triton?" He wrote. .

The discovery could also offer a clue to what New Horizons might find while exploring the Kuiper Belt, a ring of frozen debris that extends beyond Neptune's orbit (Pluto is the largest known member belt). The spacecraft is on its way to fly by Kuiper Belt Object 2014 MU69, where it could learn more about these mysterious inhabitants from the confines of our solar system.

Meanwhile, many questions remain unanswered about Pluto's methane dunes, Hayes said.

"The most notable thing is that it is not yet known how high the dunes are, when they are more active, if they change and if a trapping without elevation can occur," he wrote.

New Horizons may have pbaded through Pluto, but the theoretical work, anchored by what scientists have now learned about the dwarf planet, could shed more light on these mysterious surface features, Telfer said.


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