Mystery solved! Red patch on Pluto's largest moon Charon caused by trapped gas

Photo Credit: NASA/JHUAPL/SwRI

New Delhi: The US space agency NASA has released a high-resolution and enhanced color view of Pluto's largest moon, Charon which was captured by New Horizons spacecraft just before closest approach on July 14, 2015.

In June 2015, when the cameras on NASA's approaching New Horizons spacecraft first spotted the large reddish patch on Charon.

According to NASA, scientists think that Charon’s polar coloring comes from Pluto itself – as methane may have leaked out from Pluto's atmosphere and been trapped at Charon's pole as the moon passes through the stream of methane.

The New Horizons team has also dug into the data to determine whether conditions on the Texas-sized moon (with a diameter of 753 miles or 1,212 kilometers) could allow the capture and processing of methane gas, as per reports.

“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,” said Will Grundy, a New Horizons co-investigator from Lowell Observatory in Flagstaff, Arizona, and lead author of the paper. But while the methane ice quickly sublimates away, the heavier hydrocarbons created from it remain on the surface.

The models also suggested that in Charon’s springtime the returning sunlight triggers conversion of the frozen methane back into gas. But while the methane ice quickly sublimates away, the heavier hydrocarbons created from this evaporative process remain on the surface.

Sunlight further irradiates those leftovers into reddish material – called tholins – that has slowly accumulated on Charon’s poles over millions of years. New Horizons’ observations of Charon’s other pole, currently in winter darkness – and seen by New Horizons only by light reflecting from Pluto, or “Pluto-shine” – confirmed that the same activity was occurring at both poles.

“This study solves one of the greatest mysteries we found on Charon, Pluto’s giant moon,” said Alan Stern, New Horizons principal investigator from the Southwest Research Institute, and a study co-author. “And it opens up the possibility that other small planets in the Kuiper Belt with moons may create similar, or even more extensive ‘atmospheric transfer’ features on their moons.”