Pluto is proving to be a lot weirder than anyone ever imagined. The dwarf planet at the edge of our solar system is now thought to have winds and dunes on its surface, and there's a new theory that it was made from the collision of a billion comets.
The new findings from scientists working on NASA's New Horizons mission and ESA's Rosetta spacecraft are another twist in the tale of this distant body, once called a planet, then demoted to dwarf planet, and now being dubbed by some a "supercomet".
The core of the comet idea is that the amount of nitrogen inside the huge glacier that sprawls across Pluto is consistent with the amount that would be expected if it had been formed by the collision and agglomeration of a billion bodies like 67P/Churyumov–Gerasimenko, the famous duck-shaped comet that was orbited by Rosetta and landed on by Philae.
The researchers at SwRI in Texas aren't ruling out other theories for the formation of Pluto, which sits far out at the edge of the solar system in the Kuiper Belt. It could have been made from lumps of ice with a chemical composition closer to that of our Sun.
Meanwhile, British researcher Matt Telfer from the University of Plymouth has published a paper about what appear to be dunes on a plain on Pluto called Sputnik Planitia.
To have dunes means this dwarf planet must also have an atmosphere dense enough for winds to push grains of frozen methane particles into ridges.
The research is yet another moment to reflect on just how surprisingly diverse Pluto has been revealed to be. Until the New Horizons spacecraft flew past it in 2015, humanity had very little knowledge about this body, and many were expecting a rather dull, icy asteroid. What they got was an icy world with a giant heart-shaped plain and water-ice mountains, and hints of geological activity deep below the surface.
The dunes are something else that Pluto would have in common with comet 67/P, which stunned scientists with its combination of rippled dusty flanks and sharp-edged cliffs. In 2014 and 2015 ESA's Rosetta followed the comet around the Sun and witnessed active jets of material flying from its surface.