Scientist for a Day

Patricia Lopez-Alvarez

Grade: 6

School: Homeschooled

City: Columbia, SC

Topic: Charon

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"I believe we should send a mission to Charon, Pluto’s largest moon. The side that faces Pluto is mostly covered in organic macromolecules, and we suspect it had a liquid subsurface ocean. With both organic matter and water, could it have harbored life?

Pluto and its largest moon Charon are a binary system. This means that Pluto and Charon orbit around a common point in space, called a barycenter. Because of how close they are—19,000 km—, tholins transfer from Pluto’s atmosphere to Charon’s north pole, to the region we call Mordor Macula, which is covered in these macromolecules creating a red-brown area. Tholins are organic macromolecules produced from methane, nitrogen, and other gases in Pluto’s atmosphere. These gases, along with carbon monoxide, have been found in solid form covering Pluto’s surface in water ice. All these materials are essential elements for life.

​Furthermore, we suspect that about 4 billion years ago Charon had a subsurface liquid ocean. At the time, it was still being kept warm from radioactive particles decaying, but it started gradually freezing when there were no radioactive particles left. This process is probably what caused the massive unexpected expansion that formed the canyons, mountains, and valleys that are on its surface now. The best indication we have of the existence of this ocean is the presence of cryogeysers that have been spotted on Charon’s surface. These cryogeysers occur when water breaks through Charon’s thick ice surface and then freezes in contact with Charon’s gelid surface.

Liquid water is an essential component for life. If tholins found their way into Charon’s oceans, would that have increased the chances for life to develop? And if Charon used to be a part of Pluto, could some of the tholins from Pluto have been transported to Charon’s subsurface ocean? The temperature on Charon is -220˚C (53 K), but was the subsurface ocean warm enough for life once?

To expand our knowledge about these subjects and answer all these questions, we need to send a probe—or rover—and for that we would have to overcome many challenges. For instance, Charon is very far away from the sun, so we would need to rely on radioisotope thermoelectric generators (RTG) instead of solar power. An RTG is an electric generator that uses radioactive material to produce energy from radioactive decay and transforms it into electricity to power probes or rovers.

Fortunately, Pluto and Charon are very close to one another, so we can send a spacecraft with two rovers and probes and land them at the same time on both planetoids. If we send a mission—a spacecraft with two rovers—to Charon and Pluto using a radioisotope power system, it will provide us an opportunity to study more about Charon’s landscape and search for signs of present or past water by analyzing the cryogeysers’ ejecta composition. We could also study in depth how the binary system works and how tholins travel 19,000 km to form Mordor Macula."