Pluto is an eerie valley world with landscapes and views that look strikingly similar to those of Earth – until you take a closer look.
NASA's New Horizons mission, which flew onto the dwarf planet in July 2015, found that Pluto has huge mountains, but rather water ice than rocks; wide levels of frozen nitrogen and other exotic materials; and blue sky through a thin atmosphere that contains no significant oxygen.
And now a new study shows another extraterrestrial parallel: Pluto has a vast dune system, but the grains that make up the windswept hills are not sand. [Destination Pluto: NASA’s New Horizons Mission in Pictures]
The new discovery "shows us that Pluto's atmosphere and surface interact in a way that geologically / geomorphologically changes the surface," said study leader Matt Telfer, a lecturer in physical geography at the University of Plymouth in England.
"This is exciting, not only because it (again) shows the dynamics of these small, cold, dark, distant worlds, but also for its conclusions for very early solar system bodies," said Telfer Space.com via email.
Where Mountains Hit the Plains
Telfer and his colleagues analyzed the images captured by New Horizons during their epic flyby. They noticed within Sputnik Planitia a complex of ridges, a 620-mile-wide (1
The ridges curl in a 47-mile-wide (75 km) splinter on the western edge of Sputnik Planitia, where the plain joins the 5 km long Al-Idrisi Montes Mountains. The newly identified features are very similar to the wind-sculpted dunes, and that's exactly what they are, according to the study team.
"We are safe," Telfer said. "It's actually the relatively simple stuff, like its location, orientation (undisturbed by glacier movement, as opposed to the sublimation pits elsewhere), orientation (including neighboring orthogonal wind strips), and changes in regional orientation and distances that nail it perfectly Flair for dunes and does not match what we would see for sublimation pits. "
" Sublimation pits "are places where sunlight sublimes relatively large amounts of icy material or passes directly from the solid phase to the atmosphere. New Horizons images have revealed thousands of such depression over Sputnik Planitia, and a series of aligned pits was the most appropriate alternative explanation for the dune features that Telfer and his colleagues wrote in the new study, which was published online today (May 31 ) in the journal Science.
Sublimation is an important part of dune history, the researchers found. They carried out modeling work suggesting that Pluto's winds were strong enough to produce the Sputnik-Planitia dune system – as long as the grains being blown were already in the air. The sublimation is the only way to achieve this, with the grains being aerated by the rising gas, according to the study team.
The wind-driven grains are probably frozen methane produced in the nearby mountain range. But nitrogen stinging is another option, the authors wrote.
The lack of craters that sputters Sputnik Planitia shows that the surface of the ice surface has recently been characterized by geological activity. And the dunes are probably young too; The study team believes that they have formed within the last 500,000 years. [Pluto’s Heart: A Cosmic Valentine in Photos]
A Surprising Find
Dune systems seem to be widespread throughout the solar system. Such features have been confirmed, for example, on Earth, Mars, Venus, and Saturn's Giant Moon Titan, and may even exist on Comet 67P / Churyumov-Gerasimenko, which was studied near the European Rosetta mission from 2014 to 2016.
However, the discovery of the dunes on Pluto was unexpected given the very thin air of the dwarf planet.
"What makes this discovery surprising is that the sediment, despite Pluto's weak atmosphere, can be mobilized with a surface pressure (1 Pa) is a factor of 100,000 times lower than that on Earth," wrote Alexander Hayes, an assistant professor of Astronomy at Cornell University, who was not involved in the new study, in an accompanying "Perspectives" piece in the same issue of Science.
Telfer expressed similar feelings: "It was hard to see how the wind can affect anything until you do the math."
The new study is far from the last word on Pluto's dunes, emphasized Hayes, who also directs Cornell's Spacecraft Planetary Imaging Facility
"Nature tends to look at a number of relatively few forms and generic patterns using a variety of processes, "he wrote. "There is still a lot of work to do to understand the dunes on Pluto, but above all, it has to be shown how high the dunes are, when they are most active, if they change and if entrainment can take place without lofts."
Incidentally, the work of New Horizons is far from complete. The probe is now preparing for a flyby of a small object called the 2014 MU69, which is about 1.6 billion kilometers beyond Pluto. This close encounter, which will take place on January 1, 2019, is at the heart of the expanded mission of New Horizons.