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November 14, 2014

Pluto’s Exotic Chemistry

Reggie HudsonReggie Hudson
NASA Research Scientist

My connection to Pluto and Charon is quite different from that of other scientists who write for the New Horizons website. Certainly I’m excited about the chance to visit and study objects in the outermost of our solar system’s three major regions. Who wouldn’t be? There can only be one first encounter and we’re now about to experience it, with all the suspense and surprises that it will entail. It will be a scientific-historical event that present and future generations will remember as our first encounter with the ancient worlds of the Kuiper Belt.

Pluto landscape

In Pluto – depicted in this artist’s impression – New Horizons will encounter a world with a surface dominated by solid nitrogen, carbon compounds, and radiation-chemical products unlike any planet yet visited.

(Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Steve Gribben)

All that said, my own New Horizons experience will be colored by my background as a laboratory physical chemist. Imagine the Earth's nitrogen-dominated atmosphere moved about 30 times farther from the Sun than where you are right now. At that distance, the temperature is so low (-380 °F, -229 °C, 44 K) that the nitrogen gas, and other components of the atmosphere, would freeze into solid form, and that’s what we see on Pluto. We also know that two carbon-containing materials are present with Pluto’s frozen nitrogen, namely methane (CH4) and carbon monoxide (CO). And intriguingly, Pluto's surface has been bombarded with cosmic rays, high-energy radiation, for over four billion years, which will alter the surface’s composition and appearance in ways we can barely discern with even our most powerful telescopes.

So that’s what New Horizons will encounter next year, a world with a surface dominated by solid nitrogen, carbon compounds, and radiation-chemical products unlike any planet yet visited – and I’ll be ready. For more than 20 years I’ve worked in NASA laboratories studying various molecular ices to understand how radiation drives their evolution in Pluto's cold environment. Our experiments have given us some interesting answers and hints, and observational astronomers have given us others. However, the 2015 New Horizons encounter will deliver revolutionary insights into Pluto’s exotic chemistry – and I’ve not even mentioned the mysteries that await on Pluto’s equally exciting moon Charon!

Reggie Hudson is a research scientist and associate chief of the Astrochemistry Laboratory at NASA Goddard Space Flight Center in Greenbelt, Md. His research consists of the study of low-temperature chemistry, including the action of ionizing radiation on planetary and interstellar objects. He has received a NASA grant to investigate Pluto-Charon ice chemistry in collaboration with New Horizons co-investigator Will Grundy.