Dunes on Pluto made of tiny frozen grains of methane

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 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 located 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 already have 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 via email Thursday.

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 230 degrees Celsius (minus 400 degrees Fahrenheit) 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.