Nitrogen, Methane Dominate Icy Surface of Eris

Newswise — A team of scientists at Northern Arizona University, Missouri State University and Flagstaff’s Lowell Observatory recently revealed that the frozen surface of Eris, the largest-known dwarf planet orbiting the sun, is predominantly covered in nitrogen ice, similar to the surface of Pluto.

Stephen Tegler, NAU professor of physics and astronomy and lead author of “Methane and Nitrogen Abundances on Eris and Pluto,” will present the team’s findings Oct. 5 at the 42nd annual meeting of the American Astronomical Society’s Division for Planetary Sciences in Pasadena, Calif.

The paper also was submitted for publication to the Astrophysical Journal.

Tegler’s results integrated two years of work conducted in NAU’s new ice lab, in addition to astronomical observations of Eris from the Multiple Mirror Telescope Observatory from Mount Hopkins, Ariz., and of Pluto from Steward Observatory from Kitt Peak, Ariz.

“There are only a handful of such labs doing this kind of work in the world,” Tegler said. “By studying surfaces of icy dwarf planets, we hope to get a better understanding of the processes that affect their surfaces.”

NAU’s ice lab grew optically clear ice samples of methane, nitrogen, argon, methane-nitrogen mixtures and methane-argon mixtures in a vacuum chamber at temperatures as low as minus 390 degrees Fahrenheit to simulate the planets’ cold surfaces. Light passed through the samples revealed the “chemical finger prints” of molecules and atoms, which were compared to telescopic observations of sunlight reflected from the surfaces of Eris and Pluto.

“By combining the astronomical data and laboratory data, we found about 90 percent of Eris’s icy surface is made up of nitrogen ice and about 10 percent is made up of methane ice, which is not all that different from Pluto,” said David Cornelison, coauthor and physicist at Missouri State University.

Discovered in 2003 and named after the goddess of warfare and strife, Eris hit the astronomical map with the largest diameter of any known dwarf planet, consequently unseating its smaller neighbor Pluto from “official” to dwarf planet status. Since then, Eris has held the attention of astronomers and physicists as they strive to gain a better understanding of the farthest reaches of the solar system.

The recent findings will directly enhance NASA’s New Horizons spacecraft mission, currently scheduled to fly by Pluto in 2015, lending greater value to the continued research of Eris and Pluto.

William Grundy, an astronomer at Lowell Observatory, is a member of NASA’s New Horizons Team and contributing author of the paper.

“By measuring and then comparing and contrasting the properties of Eris and Pluto, we can better understand how planets in the outer solar system formed and then evolved over the last 4.5 billion years,” Grundy said.