Geology of Charon

In 2007, observations by the Gemini Observatory of patches of ammonia hydrates and water crystals on the surface of Charon suggested the presence of active cryogeysers.

Photometric mapping of Charon's surface shows a latitudinal trend in albedo, with a bright equator band and darker poles.

[7] The north polar region is dominated by a very large dark area informally dubbed "Mordor" by the New Horizons team.

Different time periods were labelled Ozian (older than 4 billion years, exposed in a region titled Oz Terra).

According to the hot start model, Charon accreted rapidly (within ~104 years) from the circumplanetary disc, resulting from a highly-disruptive giant impact scenario.

This rapid time scale prevents the heat from accretion from radiating away during the formation process, leading to the partial melting of Charon's outer layers.

A liquid subsurface ocean forms during or soon after Charon's accretion and persists for approximately 2 billion years before freezing, possibly driving cryovolcanic resurfacing of Vulcan Planitia.

Radiogenic heat from Charon's core could then melt a second subsurface ocean composed of a eutectic water-ammonia mixture before it too freezes, possibly driving the formation of Kubrick Mons and other similar features.

These freezing cycles could increase Charon's size by >20 km, leading to the formation of the complex tectonic features observed in Serenity Chasma and Oz Terra.

Approximately 100-200 million years after formation, enough heat builds up to where a subsurface ocean melts, leading to rapid differentiation, further contraction, and the hydration of core rocks.

After this period, differentiation continues, but the core can no longer absorb more water, and thus freezing at the base of Charon's mantle begins.