An asphalt-like layer may be baking beneath Pluto's crust. Researchers are considering the possibility that the most famous dwarf planet may contain a layer of organic material beneath its surface heated into a thick, tar-like substance. The idea, which remains speculative, could affect scientists' understanding of how Pluto is built.
Because Pluto was born in the icy Kuiper Belt beyond Neptune's orbit, it could contain organic material, particularly carbon, similar to that found in comets. If such a layer exists beneath the surface, heat and pressure could cook it into a thick, gooey material, said Bill McKinnon, a planetary scientist at Washington University in St. Louis, who presented the idea in December at the American Geophysical Union meeting in New Orleans.
"Organic matter, when you cook it, the end product is either amorphous carbon or graphite," said McKinnon, who is also a member of the research team for the New Horizons spacecraft, which flew by Pluto in July 2015. The product could also be more like thick, gooey asphalt, which is what you get when you include the heaviest fraction of the carbon-based substance petroleum. [Destination Pluto: NASA's New Horizons Mission in Pictures]
"It's not something that would be impossible inside the warmer parts of large, icy satellites and places like Pluto," McKinnon said.
McKinnon stressed that this was an idea, not a confirmed finding. When presenting the idea, his goal was to bring the possibility of an organic layer to the attention of other scientists, in hopes of sparking further models and experiments that could investigate whether such a layer might exist within Pluto.
Hot asphalt in the ocean?
Exploring the layers of planets and other celestial bodies remains a challenge. On worlds like Earth and the moon, seismometers can track how long it takes waves generated by earthquakes to travel through the crust and mantle. Because the waves travel at different speeds depending on what material they are passing through, scientists can use these waves to determine the approximate makeup of the layers beneath the surface. The Apollo missions placed wave-tracking instruments on the moon, and NASA's Mars 2020 rover will carry one to the Red Planet.