A new explanation for Pluto's moon Charon's reddish north pole

Purdue University researchers have proposed a novel idea to explain why Pluto's moon Charon has a reddish north pole. Stephanie Menten, Michael Sori, and Ali Bramson present their analysis of the reddish surfaces of various ice objects in the Kuiper Belt and how they can connect to Charon's reddish pole in a report published in the journal Nature Communications. A previous study has revealed that many ice objects in the Kuiper belt are partially or completely coated in reddish brown material. A previous study has also revealed that the substance is a kind of tholin compound, which is generated when organic molecules are exposed to radiation. However, this has raised the question of where the organic chemicals may have originated. The researchers hypothesize that it is caused by methane emitted by cryovolcanoes in this new endeavor.

To put their idea to the test, the researchers looked to Pluto's moon Charon, which has tholin covering its north pole. A previous study implies that gases escaping from Pluto are to blame for the reddish pole. However, a previous study has revealed that the moon was previously covered in a liquid ocean containing a variety of elements, including methane. The methane would have been trapped in the ice as the water froze, according to the researchers. They also remark that when the water grew pressured, fissures occurred, resulting in rare explosions. They believe that such cryovolcanic eruptions may have produced some methane gas. And if part of the methane gas made it all the way to the north pole, it would have frozen and plummeted to the ground. If it dropped to the surface, it would have been exposed to millions of years of solar radiation, turning it crimson.

The researchers developed models of methane molecules drifting around in the Charon atmosphere, calculating how much methane may have escaped and how much might have made it to the north pole under such a scenario. They discovered that around 1000 billion metric tons of the gas may have made it to the northern pole, which would have been more than enough to form a crimson cap.

Journal Information: Stephanie M. Menten et al, Endogenically sourced volatiles on Charon and other Kuiper belt objects, Nature Communications (2022). DOI: 10.1038/s41467-022-31846-8