A Cryovolcanic Origin for Mordor Macula on Charon
Abstract
Cryovolcanism is a poorly understood type of volcanic process that occurs on icy bodies in our solar system and could be important in how a planetary body geologically evolves. Charon, the largest moon of Pluto, displays evidence of widespread cryovolcanic activity. Charon is thought to have been geologically active until around 4 Ga when its subsurface ocean froze. The freezing of Charons subsurface ocean led to extensive cryovolcanic resurfacing in the southern hemisphere, resulting in the geologic unit known as Vulcan Planitia. Charon additionally contains a polar region called Mordor Macula characterized by its dark red color that hosts organic molecules. These organic molecules are proposed to be methane processed by radiation and are called tholins. Grundy et al. [2016] proposed that the source material for Mordor Macula came from Plutos atmosphere. We instead propose that the emplacement of Vulcan Planitia cryolavas supplied sufficient methane to source Mordor Macula. We examined geologic features within Vulcan Planitia to estimate the thickness, volume, and methane content of the cryoflow. These features included craters with infill, troughs surrounding mountain features, and tectonic grooves. We then developed a volatile transport model to determine the likelihood of methane migrating to Charons north pole, and found that in northern winter around 97% of the methane sourced from Vulcan Planitia will reach the Mordor Macula region, while 3% escapes to space. Methane ice would be deposited at a rate around 2 mm per Charon year, assuming Vulcan Planitia is emplaced over 1 Myr. Over the entire emplacement of Vulcan Planitia, an integrated total thickness of 9 meters of methane ice would be supplied to each pole. We find that the emplacement of Vulcan Planitia and subsequent volatile transport and deposition of methane to Charons poles is sufficient to have supplied the necessary material to have sourced the tholins of Mordor Macula. Other KBOs have analogous red features, so cryovolcanically sourced volatiles could be important across the Kuiper Belt.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.P45C2449M