Image copyright NASA / JHUAPL / SWRI Image caption The data from New Horizons revealed Pluto to be geologically diverse and dynamic

Scientists say they have found evidence of dunes of frozen methane on Pluto.

The research, which is published in the journal Science, suggests that the distant world is more dynamic than previously thought.

Pluto's atmosphere was believed to be too thin to create the features familiar in deserts on Earth.

The findings come from analysis of the startling images sent back by Nasa's New Horizons mission, which flew close to Pluto in July 2015.

After an epic trek through the Solar System that took nearly a decade, New Horizons sped by at a speed of 58,536 km/h (36,373 mph), gathering data as it passed.

In their study, the researchers explain how they studied pictures of a plain known as Sputnik Planitia, parts of which are covered with what look like fields of dunes.

They are lying close to a range of mountains of water ice 5km high.

The scientists conclude that the dunes are 0.4-1km apart and that they are made up of particles of methane ice between 200-300 micrometers in diameter - roughly the size of grains of sand.

Image copyright NASA / JHUAPL / SWRI Image caption Dunes can be seen in the bottom half of this picture of Pluto's Sputnik Planitia region

The paper's lead author is Dr Matt Telfer, a physical geographer at the University of Plymouth. He told BBC News: "We can't see individual grains but what we are able to identify dunes, and characterise their basic physical parameters, and the density of the atmosphere that they've been formed under.

"And we can measure some basic things like how far apart they are spaced, and have an estimate at least of the wind speeds that are forming them.

"We can feed all that back into a physical model and from that deduce what the size of the grains must be."

To be able to form, dunes need an atmosphere dense enough to make wind transport possible, a supply of dry particles, and a mechanism that lifts particles off the ground.

At first sight, none of those conditions seem to be met on Pluto.

But Dr Telfer and his colleagues calculate that the dunes may be in one of the windiest areas of the Pluto with wind speeds reaching up to 10m/sec - enough to keep particles moving.

Image copyright NASA / JHUAPL / SWRI Image caption Pluto's atmosphere was thought to be too thin to create dunes through the action of wind alone

Image copyright NASA / JHUAPL / SWRI Image caption Pluto's strange "snakeskin terrain" may represent not dunes, but blades of ice

The wind is generated as air flows downhill from the neighbouring mountains and also as frozen material sublimates - or turns directly into gas.

They believe that the dunes are composed of grains of methane, and maybe of nitrogen as well, and that a "reservoir" of methane may exist in the snowpack of the mountains.

As for the process of "lofting" the grains off the ground, the paper suggests that the driver could be a slight warming from the distant Sun, raising the temperature above the frost point of nitrogen: -230C.

With that warming of the ice below the surface, methane crystals should enable nitrogen ice to sublimate - and that would allow the methane crystals to be wafted into the atmosphere.

Dr Telfer says the analysis provides a new insight to Pluto and also changes our view of it.

"It's really exciting just to be able to look at this world and recognise that it's not just a frozen icy blob in the outer reaches of the Solar System but really we're seeing a dynamic world still changing, still forming today," he said.

Image copyright NASA/JHUAPL/SwRI/Steve Gribben Image caption Artwork: New Horizons will fly past the Kuiper Belt object 2014 MU69 in January 2019

That sentiment is echoed in an article accompanying the Science paper by Prof Alexander Hayes, an astronomer at Cornell University in Ithaca, US.

He quotes the late Sir Patrick Moore, the famous BBC Sky at Night presenter, describing Pluto in 1955 as "…plunged in everlasting dusk, silent, barren, and touched with the chill of death…" and says that that perspective has to shift.

Prof Hayes says we now know Pluto to be "a geologically diverse and dynamic world driven by internal heat, extreme seasons and sublimating ices".

He adds that it's not the frontier of the Solar System as Patrick Moore suggested, but the "gateway" to the unexplored realm of the Kuiper Belt.

And it may be that dunes themselves are emerging as a fascinating new feature of space exploration.

Image copyright NASA / JHUAPL / SWRI

Pluto now joins Earth, Mars, Venus, Saturn's moon Titan and even the comet 67P - which a European Space Agency (Esa) mission landed on - as homes to dunes.

And Prof Monica Grady of the Open University told me that the discovery raises fascinating questions about whether there are dunes on worlds in other star systems too.

"It makes you realise that you have to open your mind to the idea that familiar objects on different planetary bodies must have formed in their own ways," she said.

"What it does is lead you to thinking about what's there beyond the Solar System, because we can't see their surfaces at the moment but we will do and then we'll probably see familiar things - we'll see dunes and they'll remind us of the dunes of Pluto or the dunes on Earth but they'll have formed in a different way."

New Horizons is now approaching another object in the Kuiper Belt, known as 2014 MU69. The spacecraft will be brought out of hibernation next week and a fly-past is scheduled for Jan 1 2019.

Follow David on Twitter.</s>Sand dunes are found all over Earth: along the shores of lakes or oceans, deserts like the Sahara in Africa, and even underwater. Robotic space probes have also found dunes on Venus, Mars, and Saturn's giant moon Titan.

Now researchers think they have found dunes on Pluto, which presents a huge (and fun) mystery. How can dunes form on a world where the atmosphere is a bare wisp, not enough to create the kind of winds responsible for making dunes elsewhere in the Solar System?

As described in a new paper published in Science, these possible dunes might be made when methane ice crystals get lofted into Pluto's thin atmosphere and pushed ever so slightly by the winds.

The most famous feature on Pluto is its "heart", more formally known as Sputnik Planitia. This region is remarkably smooth compared with the mountains surrounding it, but when researchers examined the high-resolution images taken by the New Horizons spacecraft in 2015, they found wrinkles.

In other words, Pluto's possible dunes don't seem to come from the same processes that make dunes elsewhere in the Solar System ... with one possible exception. Scientists looking images of Comet 67P/Churyumov-Gerasimenko found something that looks like dunes. Comet 67P has no real atmosphere, but it does have jets of material that occasionally shoot away from the surface.

That's similar to what the authors of the new paper propose for Pluto. Sputnik Planitia is made of ice, but not water ice: it's mostly nitrogen, with some carbon monoxide and methane thrown in. The hypothesis: when the Sun shines on Pluto's heart, the methane ice sublimates (melting directly from solid to gas, without turning into a liquid first), throwing small plumes into the atmosphere. The tiny amount of wind then is enough to push the methane crystals into dunes when they fall back down to the surface.

To be fair, the wrinkles on Pluto's heart might not be dunes: they might be created by some other process (though the authors take care to rule out some other possibilities, like erosion). The dune hypothesis is a fun one, however, not least because it reinforces the idea that dunes pretty much form on any object with a solid surface with grains that can be piled up. What we don't know yet would settle the issue: how tall these dunes are, whether they move around, or if they formed ages ago and froze that way.

Whether or not we call Pluto a planet is by far the least interesting thing about it. After all, this tiny iceball seems to be geologically active, with potential volcanoes, moving glaciers, and now methane-ice dunes. The little odd world on the edge of the explored Solar System has turned out to be mysterious in the most fun way possible for scientists.</s>Scientists have discovered dunes on Pluto made of tiny frozen grains of methane.

Scientists have discovered dunes on Pluto made of tiny frozen grains of methane.

A British-led team announced the findings on Thursday in the journal Science. Researchers said the dunes appear to be made mostly of icy specks of methane the size of sand, with some frozen nitrogen likely mixed in.

Thought to be relatively recent, the parallel rows of dunes are in Pluto’s heart-shaped region at the base of mountains as tall as the Alps and formed from giant blocks of ice with frosty methane snowcaps. These plains in the left lobe of Pluto’s “heart” are known as Sputnik Planitia.

Scientists were surprised to find dunes given Pluto’s thin, weak atmosphere. They suggest nitrogen ice coating the surface of Sputnik Planitia transformed into gas that lifted methane particles into the air. Pluto’s gentle winds then carried and deposited the grains. Dunes have already been found on Mars, Venus, Saturn’s moon, Titan and even a comet. But Pluto’s are the only ones known to consist of methane.

“Pretty much nowhere else we know of is cold enough!” the study’s lead author, Matt Telfer of Plymouth University in England, said. We are back! To start your Tuesday off right, check out this super cool image of haze layers above Pluto’s limb taken by the Ralph/Multispectral Visible Imaging Camera (MVIC) on the #NewHorizons spacecraft! https://t.co/G15Ltcy7Gh pic.twitter.com/L1fu00xWND — NASA New Horizons (@NASANewHorizons) January 23, 2018 He noted there are dunes on the scorching surface of Venus under a dense atmosphere and out in the distant reaches of the solar system at minus 230C (minus 400F) under a thin atmosphere.

“These are not just balls of ice far out in space,” he said, adding that frozen worlds on the fringes of our solar system, like the dwarf planet Pluto, might have been active early on.

“It’s a little bit lower density than sand we’re used to holding on the Earth,” Brigham Young University’s Jani Radebaugh, a co-author, explained by phone. “So it would feel lighter in your hand, but it would still be granular and would kind of flow off of your hand, and your feet would kind of crunch them as you’re walking along. It would just kind of feel a lot like you’re on another sand dune on the Earth.”

“Much work is left to do to understand dunes on Pluto,” Cornell University’s Alexander Hayes wrote in a companion article. “Most notably, it remains to be shown how high the dunes are, when they are most active, whether they change” and whether particles can be swept into dunes without rising into the air. Nonetheless, he described the Telfer team’s argument for uplifted methane granules as convincing.

Launched in 2006, New Horizons was the first spacecraft ever to visit Pluto, passing within 7,770m (12,500km). It is now heading towards an even more distant world in our solar system’s so-called Kuiper Belt, or Twilight Zone. It’s expected to zip past the Kuiper Belt object nicknamed Ultima Thule — orbiting a billion miles (1.6 billion km) beyond Pluto — on January 1.</s>CAPE CANAVERAL, Fla. (AP) - Scientists have discovered dunes on Pluto made of tiny frozen grains of methane.

The pale gray and white ridges were revealed by NASA's New Horizons spacecraft during its 2015 flyby. A British-led team announced the findings Thursday in the journal Science.

Researchers say the dunes appear to be made mostly of icy specks of methane the size of sand. Thought to be relatively recent, the dunes are located in Pluto's heart-shaped region at the base of mountains with methane snowcaps.

This July 2015 image made by the New Horizons spacecraft shows dunes, small ripples at bottom right, on Pluto's Sputnik Planitia ice plain. At upper left are a series of mountains. Researchers say the dunes appear to be made mostly of icy specks of methane the size of sand. Thought to be relatively recent, the dunes are located in Pluto's heart-shaped region at the base of water ice-block mountains with methane snowcaps. (NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute via AP)

Scientists were surprised to find dunes given Pluto's thin, weak atmosphere. They suggest surface nitrogen ice transformed into gas that lifted methane particles. Pluto's gentle winds then carried and deposited the grains.

Dunes already have been found on Mars, Venus, Saturn's moon, Titan, and even a comet.</s>Pluto got taken off the list of the solar system’s planets a few years ago, but that does not make it any less of an interesting body for astronomers to study. And scientists sifting through data gathered by NASA’s New Horizons spacecraft have now found the dwarf planet is home to surface dunes, made of methane.

Other than Earth, dunes are known to form on several other terrestrial bodies in the solar system, including Mars and Venus, Saturn’s largest moon Titan, as well as on the comet 67P. Unlike the sand dunes on Earth, though, these formations on Pluto are made up solid methane, or grains of methane ice. Based on the data that New Horizons captured during its 2015 flyby of Pluto, scientists surmised the methane grains are released into the dwarf planet’s thin and rarefied atmosphere when solid nitrogen gets converted directly into gas (a process called sublimation).

A detailed look at images of Pluto showed researchers the methane dunes spread across an area that forms the boundary between the icy plain called Sputnik Planitia (one of the largest features on Pluto) and a major mountain range that lies next to it. The area where the dunes are is about 75 kilometers (47 miles) across.

“We knew that every solar system body with an atmosphere and a solid rocky surface has dunes on it, but we didn't know what we'd find on Pluto. It turns out that even though there is so little atmosphere, and the surface temperature is around -230 degrees Celsius, we still get dunes forming. The New Horizons data has given us a new level of detail, but we had to work hard to explain how it was possible to get the supply of sediment, a non-cohesive surface and wind you need for dunes,” Matt Telfer, from the University of Plymouth in the United Kingdom and lead author of the paper describing the formations, said in a statement Thursday.

The dunes were seen as hundreds of ridges in New Horizons’ images, appearing parallel to the mountain range in the western portion of the plain, but changing orientation and becoming spread out as they moved eastward. Wind streaks, six in all, were also seen in the images, and they showed a similar pattern to the ridges. The dunes likely formed in the last 500,000 years, maybe a lot more recently.

The methane grains that make up the dune likely come from the mountain range, but they could also be nitrogen ice instead, according to the authors of the study. Even as the winds on Pluto reach maximum speeds of 30 to 40 kilometers an hour, they are sufficient, given the low surface pressure (100,000 times less than Earth) and weak gravity, for the dunes to form.

Simply titled “Dunes on Pluto,” the paper appeared online Thursday in the journal Science. An additional perspective was published too, titled “Dunes across the solar system.”</s>CAPE CANAVERAL, Fla. - Scientists have discovered dunes on Pluto made of tiny frozen grains of methane.

The pale grey and white ridges were revealed by NASA's New Horizons spacecraft during its 2015 flyby. A British-led team announced the findings Thursday in the journal Science.

Researchers say the dunes appear to be made mostly of icy specks of methane the size of sand. Thought to be relatively recent, the dunes are located in Pluto's heart-shaped region at the base of mountains with methane snowcaps.

Scientists were surprised to find dunes given Pluto's thin, weak atmosphere. They suggest surface nitrogen ice transformed into gas that lifted methane particles. Pluto's gentle winds then carried and deposited the grains.

Dunes already have been found on Mars, Venus, Saturn's moon, Titan, and even a comet.</s>Scientists have discovered dunes on Pluto made of tiny frozen grains of methane. The pale gray and white ridges were revealed by Nasa’s New Horizons spacecraft during its 2015 flyby. A British-led team announced the findings on Thursday in the journal Science. Researchers said the dunes appear to be made mostly of icy specks of methane the size of sand, with some frozen nitrogen likely mixed in.

Thought to be relatively recent, the parallel rows of dunes are in Pluto’s heart-shaped region at the base of mountains as tall as the Alps and formed from giant blocks of ice with frosty methane snowcaps. These plains in the left lobe of Pluto’s “heart” are known as Sputnik Planitia. Scientists were surprised to find dunes given Pluto’s thin, weak atmosphere. They suggest nitrogen ice coating the surface of Sputnik Planitia transformed into gas that lifted methane particles into the air. Pluto’s gentle winds then carried and deposited the grains. Dunes have already been found on Mars, Venus, Saturn’s moon, Titan and even a comet. But Pluto’s are the only ones known to consist of methane. “Pretty much nowhere else we know of is cold enough!” the study’s lead author, Matt Telfer of Plymouth University in England, said.

He noted there are dunes on the scorching surface of Venus under a dense atmosphere and out in the distant reaches of the solar system at minus 230C (minus 400F) under a thin atmosphere. “These are not just balls of ice far out in space,” he said, adding that frozen worlds on the fringes of our solar system, like the dwarf planet Pluto, might have been active early on. Researchers liken the dunes to those at White Sands, New Mexico, or California’s Death Valley. “It’s a little bit lower density than sand we’re used to holding on the Earth,” Brigham Young University’s Jani Radebaugh, a co-author, explained by phone. “So it would feel lighter in your hand, but it would still be granular and would kind of flow off of your hand, and your feet would kind of crunch them as you’re walking along. It would just kind of feel a lot like you’re on another sand dune on the Earth.” The team has yet to determine the height of the dunes; Mr Telfer guesses they’re at least tens of metres tall.</s>Scientists have discovered dunes on Pluto made of tiny frozen grains of methane.

The pale gray and white ridges were revealed by Nasa’s New Horizons spacecraft during its 2015 flyby.

A British-led team announced the findings on Thursday in the journal Science.

Researchers said the dunes appear to be made mostly of icy specks of methane the size of sand, with some frozen nitrogen likely mixed in.

Thought to be relatively recent, the parallel rows of dunes are in Pluto’s heart-shaped region at the base of mountains as tall as the Alps and formed from giant blocks of ice with frosty methane snowcaps.

These plains in the left lobe of Pluto’s “heart” are known as Sputnik Planitia.

Scientists were surprised to find dunes given Pluto’s thin, weak atmosphere. They suggest nitrogen ice coating the surface of Sputnik Planitia transformed into gas that lifted methane particles into the air. Pluto’s gentle winds then carried and deposited the grains.

Dunes have already been found on Mars, Venus, Saturn’s moon, Titan and even a comet. But Pluto’s are the only ones known to consist of methane.

“Pretty much nowhere else we know of is cold enough!” the study’s lead author, Matt Telfer of Plymouth University in England, said.

He noted there are dunes on the scorching surface of Venus under a dense atmosphere and out in the distant reaches of the solar system at minus 230C (minus 400F) under a thin atmosphere.

“These are not just balls of ice far out in space,” he said, adding that frozen worlds on the fringes of our solar system, like the dwarf planet Pluto, might have been active early on.

Researchers liken the dunes to those at White Sands, New Mexico, or California’s Death Valley.

“It’s a little bit lower density than sand we’re used to holding on the Earth,” Brigham Young University’s Jani Radebaugh, a co-author, explained by phone.

“So it would feel lighter in your hand, but it would still be granular and would kind of flow off of your hand, and your feet would kind of crunch them as you’re walking along. It would just kind of feel a lot like you’re on another sand dune on the Earth.”

The team has yet to determine the height of the dunes; Mr Telfer guesses they’re at least tens of metres tall.

“Much work is left to do to understand dunes on Pluto,” Cornell University’s Alexander Hayes wrote in a companion article.

“Most notably, it remains to be shown how high the dunes are, when they are most active, whether they change” and whether particles can be swept into dunes without rising into the air.

Nonetheless, he described the Telfer team’s argument for uplifted methane granules as convincing.

Launched in 2006, New Horizons was the first spacecraft ever to visit Pluto, passing within 7,770m (12,500km).

It is now heading towards an even more distant world in our solar system’s so-called Kuiper Belt, or Twilight Zone.

It’s expected to zip past the Kuiper Belt object nicknamed Ultima Thule — orbiting a billion miles (1.6 billion km) beyond Pluto — on January 1.

Flight controllers at Johns Hopkins University’s Applied Physics Laboratory in Laurel, Maryland, will rouse New Horizons from a five-month electronic hibernation next week.</s>Scientists say they have found evidence of dunes of frozen methane on Pluto , suggesting that the distant world is more dynamic than previously thought. The research has been published in the journal Science . BBC reports:"The methane grains could have been lofted into the atmosphere by the melting of surrounding nitrogen ice or blown down from nearby mountains," the researchers write in the journal Science. "Understanding how dunes form under Pluto conditions will help with interpreting similar features found elsewhere in the solar system."</s>Scientists have discovered dunes on Pluto made of tiny frozen grains of methane.

The pale grey and white ridges were revealed by NASA's New Horizons spacecraft during its 2015 flyby.

A British-led team announced the findings on Thursday in the journal Science.

Researchers say the dunes appear to be made mostly of icy specks of methane the size of sand, with some frozen nitrogen likely mixed in.

Thought to be relatively recent, the parallel rows of dunes are in Pluto's heart-shaped region at the base of mountains as tall as the Alps and formed from giant blocks of ice with frosty methane snow caps.

These plains in the left lobe of Pluto's "heart" are known as Sputnik Planitia.

Scientists were surprised to find dunes given Pluto's thin, weak atmosphere.

They suggest nitrogen ice coating the surface of Sputnik Planitia transformed into gas that lifted methane particles into the air.

Pluto's gentle winds then carried and deposited the grains.

Dunes have already been found on Mars, Venus, Saturn's moon, Titan and even a comet. Pluto's are the only ones known to consist of methane.

The study's lead author, Matt Telfer of Plymouth University in the UK, noted there were dunes on the scorching surface of Venus under a dense atmosphere and in the distant reaches of the solar system at minus 230C under a thin atmosphere.

Researchers liken the dunes to those at White Sands, New Mexico, or California's Death Valley.

The team has yet to determine the height of the dunes. Telfer guesses they are at least tens of metres tall.

Launched in 2006, New Horizons was the first spacecraft ever to visit Pluto, passing within 12,500km.

It's now heading towards an object in the Kuiper Belt nicknamed Ultima Thule, about 1.6 billion kilometres beyond Pluto, on January 1.
Pluto, the eponymous member of the plutino group, is discovered to have dunes of methane ice.