Southwest Research Institute scientists assembled data from NASA’s New Horizons mission with novel laboratory tests and exospheric modeling to disclose the likely configuration of the red cap on Pluto’s moon Charon and how it may have been created. This first-ever justification of Charon’s dynamic methane environment utilizing new experimental data delivers a fascinating peek into the origins of this moon’s red spot, as depicted in two recent papers.
“Before New Horizons, the best Hubble images of Pluto revealed only a fuzzy blob of reflected light,” announced SwRI’s Randy Gladstone, a member of the New Horizons science team. “In addition to all the fascinating features discovered on Pluto’s surface, the flyby revealed an unusual feature on Charon, a surprising red cap centered on its north pole.”
Shortly after the 2015 encounter, the New Horizons scientists suggested that a reddish “tholin-like” material at Charon’s pole could be synthesized by ultraviolet light breaking down methane molecules. These are seized after fleeing Pluto and then frozen onto the moon’s polar regions during their long winter nights. Tholins are sticky organic sediments formed by chemical reactions fueled by light; in this case, the Lyman-alpha ultraviolet gleam is dispersed by interplanetary hydrogen molecules.
“Our findings indicate that drastic seasonal surges in Charon’s thin atmosphere as well as light breaking down the condensing methane frost are key to understanding the origins of Charon’s red polar zone,” announced SwRI’s Dr. Ujjwal Raut, lead author of a paper titled “Charon’s Refractory Factory” in the journal Science Advances. “This is one of the most illustrative and stark examples of surface-atmospheric interactions so far observed at a planetary body.”