Why Charon’s North Pole is Red

Admin | Published 2016-09-16 10:28
  New Horizons first spotted a dark red area on Pluto’s largest moon last June 2015. A year later, after all the analysis from data gathered, the mission scientists believe they have solved the riddle. Charon’s polar red color is caused from Pluto itself – methane gas escapes from the dwarf planet and becomes ‘captured’ by the moon’s gravitational pull and then freezes on icy surface at Charon’s North Pole, Sci-News reports. This is then followed by a chemical process with UV light from the sun that transforms methane into heavy hydrocarbons and then eventually into tholins – reddish organic materials.
“Who would have thought that Pluto is a graffiti artist, spray-painting its companion with a reddish stain that covers an area the size of New Mexico? Every time we explore, we find surprises. Nature is amazingly inventive in using the basic laws of physics and chemistry to create spectacular landscapes,” said New Horizons project scientist Dr. Will Grundy, from Lowell Observatory.
Dr. Grundy and his collective team coming from Germany, France, and the US have combined analyses from the captured images of Charon combined with computer modelling on how ice would evolve on the moon’s poles. They had hoped that methane from Pluto’s was captured in Charon’s pole and slowly molded into the reddish material, but had no support for the said theory. They excavated into the information to define whether circumstances on Charon could make this possible. The computer models show punishing weather at Charon’s poles, where continuous sunlight changes into continuous darkness in 100 year cycles. Surface temperatures when on the dark cycle dive to -430 degrees Fahrenheit (-257 Celsius), this is enough to freeze methane gas.
“The methane molecules bounce around on Charon’s surface until they either escape back into space or land on the cold pole, where they freeze solid, forming a thin coating of methane ice that lasts until sunlight comes back in the spring,” Dr. Grundy said. “But while the methane ice quickly sublimates away, the heavier hydrocarbons created from it remain on the surface.”
The models also show that during Charon’s bright cycle converts the solid methane into gas, which in the process would leave the heavy hydrocarbons on the surface. Sunlight has further irradiated the scraps into reddish tholins and after millions of years are now accumulated on Charon’s poles. New Horizons’ observations of Charon’s other pole, currently in winter darkness – and seen by New Horizons only by light reflecting from Pluto– confirmed that the same activity was occurring at both poles. The team’s will be available by this week on the journal Nature. https://www.youtube.com/watch?v=gFRjpTYxBXU  
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