Finger-print like pattern observed near al-Idrisi Montes mountain on Pluto. Photos of the area between the boundary of the Sputnik Planitia ice plain and one of Pluto's mountain ranges, however, proved those expectations wrong.
Co-author of the study, Jani Radebaugh from the Brigham Young University said in a statement that, "Dunes on Pluto, or any other body, tell us there is a significant enough atmosphere to move materials around, and that there are particles to move-in this case, frozen methane sand". They now plan to carry on investigating the dunes through computer simulations, which will in turn further enlighten them about how Pluto's winds shaped its geography. Quartz fragments commonly supply the sand for Earth dunes. "The way that they're recognizing the dunes on the surface is the same technique we've used to identify dunes on Mars". Dunes on Pluto aren't made of sand.
The dwarf planet Pluto (R) and its largest moon Charon are shown July 11, 2015 as NASA's New Horizons spacecraft was nearing its flyby. It's expected to zip past the Kuiper Belt object nicknamed Ultima Thule - orbiting 1 billion miles (1.6 billion kilometers) beyond Pluto - on January 1. This view is projected from a point 1,118 miles (1,800 km) above Pluto's equator, looking northeast over the dark, cratered Cthulhu Regio toward the bright, smooth expanse of icy plains called Sputnik Planitia.
"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 explain. The ice is a mixture of nitrogen, carbon monoxide and methane; according to the model, methane is still solid as nitrogen vaporises, and so grains of methane ice are thrown from the surface to be caught by the wind. The surface patterns recorded by New Horizons don't lie, though. The team suggests flecks of nitrogen ice from Sputnik Planitia itself are also an outside possibility.
Once airborne, the particles are pushed by winds that blow between 18 and 24 miles an hour. "Although nitrogen ice can not be ruled out". The upward force is what drives the piles of particles at the surface.
By analyzing the dunes and wind streaks and then combining the data with spectral and numerical modelling, the researchers found that sublimation - the process of turning solids to gas - creates sand-like grains of methane. In comparison with the pressure of Earth's atmosphere, the Pluto's atmosphere has got a lower surface pressure. The temperature gradients in the granular ice layer, caused by solar radiation, also play an important role in the onset of the saltation process.
Dr Eric Parteli, Lecturer in Computational Geosciences at the University of Cologne, said: "On Earth, you need a certain strength of wind to release sand particles into the air, but winds that are 20% weaker are then sufficient to maintain transport".