Icy surface of Eris dominated by nitrogen, methane

Eris is predominantly covered in nitrogen ice, similar to surface of Pluto.

Washington: Scientists have revealed that the frozen surface of Eris-largest-known dwarf planet orbiting the Sun-is predominantly covered in nitrogen ice, similar to the surface of Pluto.

The results of the study 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.

"By studying surfaces of icy dwarf planets, we hope to get a better understanding of the processes that affect their surfaces," said Stephen Tegler, lead author of the study.

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 fingerprints" 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" planet to dwarf planet status.

William Grundy, of the Lowell Observatory said: "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."

The findings were published in the Astrophysical Journal.