New Horizons data suggests mountains of nitrogen ice on Pluto have evaporated

New Horizons' latest findings: Evidence of evaporated ice mountains, and heat within Pluto.

The latest data downloaded from NASA's New Horizons spacecraft suggests that mountains of nitrogen ice thousands of feet high have evaporated into Pluto's atmosphere since the dwarf planet formed 4.5 billion years ago, and hundreds of tons of that gas escape into space each hour.

New images of Pluto meanwhile show land forms that suggest heat is rising beneath the surface, with troughs of dark matter either collecting or bubbling up between flat segments of crust.

Scientists discussed the findings Friday in their second major release of data collected when the $700 million New Horizons mission made a historic pass 7,700 miles from Pluto on Tuesday. Scientists and engineers at the Johns Hopkins Applied Physics Laboratory in Laurel are managing the mission.

They said Pluto continues to surprise and impress them.

"Pluto's becoming a brand that sort of sells itself. You don't really have to work all that hard," said Alan Stern, the New Horizons mission's principal investigator and a scientist at the Southwest Research Institute in Boulder, Colo. "I think the solar system saved the best for last."

Scientists for the first time discussed data collected on Pluto's atmosphere and on charged particles detected around the dwarf planet. They found that a stream of nitrogen is flowing away from the planet, blown by winds of charged particles released by the sun.

They estimated that about 500 tons of nitrogen escapes hourly from Pluto's atmosphere, compared with about 1 ton of gases escaping from Mars' thin atmosphere each hour, said Fran Bagenal, a co-investigator on the mission and professor at the University of Colorado, Boulder.

Images released Friday zoom in on an area at the bottom of Pluto's heart-shaped formation, named Tombaugh Regio, that is mostly flat and without craters but includes irregularly shaped segments bordered by shallow troughs. Jeff Moore, leader of New Horizons' geology science team, likened its appearance to a boiling pot of oatmeal or the material inside a lava lamp, presumably the result of heat bubbling up from beneath.

Another part of Tombaugh Regio was eye-catching because of a concentrated area of carbon dioxide ice, not found anywhere else on that hemisphere of Pluto, Stern said.

The scientists also released their first image of Nix, one of Pluto's smaller moons, which was revealed to be 25 miles across. Stern noted that the image of Nix is as good as astronomers' best image of Pluto three months ago.

More findings are scheduled to be released next Friday.

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