On July 14th, NASA’s New Horizons spacecraft completed a mission nearly a decade in the making and made a flyby of Pluto. It revealed Pluto’s beating heart and icy veins; it’s moon Charon has a space Mordor. But just seven hours after this historic meeting, New Horizons was a million miles away on the dark side of the dwarf planet.
Lucky, it took a picture to say goodbye.
This lovely, back-lit picture was taken by New Horizons around midnight EDT on July 15th from 1.25 million miles (2 million kilometers) away. Not only is it beautiful, it’s informative. It shows Pluto’s “hazy” atmosphere extending 80 miles (130 kilometers) up from the surface. That’s several times higher than NASA scientists expected.
“My jaw was on the ground when I saw this first image of an alien atmosphere in the Kuiper Belt,” said New Horizons Principal Investigator Alan Stern of the Southwest Research Institute in a press release. “It reminds us that exploration brings us more than just incredible discoveries — it brings incredible beauty.”
The hazy look comes from the breakdown of methane in Pluto’s atmosphere. This breakdown allows for the formation of larger hydrocarbon gases — gases made of longer chains of hydrogen and carbon — that subsequently sink closer to Pluto’s surface and become frozen particles, which make up the layers of haze. When ultraviolet radiation from the Sun breaks down these hazes, tholins, or dark hydrocarbons, form and bestow the Plutonian land with a reddish color.
It was a surprise when Pluto’s hazes were found so far from the surface. So much so in fact that scientists aren’t quite sure what is going on; they will need new models of Pluto to explain it. Over the next year, New Horizons will send back the rest of the data it gathered flying by the king of the Kuiper Belt, and there are sure to be more surprises in store for us.