Along the border of Sputnik Planum are what look like dark, windswept dunes, an unexpected surprise on a world that has too thin an atmosphere for wind, officials said.
"Seeing dunes on Pluto - if that is what they are - would be completely wild, because Pluto's atmosphere today is so thin," William B. McKinnon, a GGI deputy lead from Washington University, St. Louis, said in the statement. "Either Pluto had a thicker atmosphere in the past, or some process we haven't figured out is at work. It's a head-scratcher."
Researchers also received more data about Pluto's atmospheric haze. Imaged as Pluto blocked out the sun, this haze formed a glowing halo from the probe's perspective. There are more layers than the data initially suggested, and a soft atmospheric glow illuminates the planet's night side just before sunrise and after sunset.
"This bonus, twilight view is a wonderful gift that Pluto has handed to us," John Spencer, a GGI deputy lead also from the Southwest Research Institute in Colorado, said in the statement. "Now we can study geology in terrain that we never expected to see."