How dunes form on Pluto decoded

Scientists have discovered dunes on Pluto that are likely to have been formed of methane ice grains released into its rarefied atmosphere.

Detailed images of the dwarf planet's surface, captured in July 2015 by NASA's New Horizons spacecraft, showed that on the boundary of the Sputnik Planitia ice plain, and pushed up against a major mountain range, there is a series of dunes spread across an area less than 75 kilometres across.

Scientists from the University of Plymouth in the UK, University of Cologne in Germany and Brigham Young University in the US conducted spatial analysis of the dunes and nearby wind streaks on the planet's surface, as well as spectral and numerical modeling.

They believe that sublimation - which converts solid nitrogen directly into a gas - results in sand-sized grains of methane being released into the environment.

These are then transported by Pluto's moderate winds (which can reach between 30 and 40 kilometres per hour), with the border of the ice plain and mountain range providing the perfect location for such regular surface formations to appear.

The scientists also believe the undisturbed morphology of the dunes and their relationship with the underlying glacial ice suggests the features are likely to have been formed within the last 500,000 years, and possibly much more recently.

"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 minus 230 degree Celsius, we still get dunes forming, said Matt Telfer, from the University of Plymouth.

"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. It is another piece of the jigsaw in making sense of this diverse and remote body, and gives us a more fundamental understanding of the geological processes which are influencing it," said Telfer, lead author of the study published in the journal Science.

The researchers now plan to continue their investigations into the history of Pluto's dunes through computer simulations, which will enable them to expand knowledge of the role wind has played in Pluto's wider geology.