Weird Red Spot on Pluto's Moon Charon Caused by Traveling Atmosphere

Pluto may be sharing its atmosphere with its largest moon, Charon, creating the visually striking red spot at the satellite's north pole. New research suggests that conditions on the two worlds over the past few billion years would allow Pluto's traveling atmosphere to freeze out on the frigid moon Charon, while radiation would quickly transform the methane and nitrogen ices to a sticky residue known as tholins. "Methane is volatile enough that it can only stick to the surface during the long, c