by MIKE WALL and SPACE.COM
Pluto IMAGE/NASA
New Horizons team members released other new photos and information today as well. For example, they revealed that the west side of Pluto’s “heart” is rich in carbon-monoxide ice, unlike the rest of the dwarf planet, and they announced that the probe had detected Pluto’s thin, nitrogen-dominated atmosphere out to a distance of 1,000 miles (1,600 km) from the surface.
Furthermore, New Horizons spotted a cloud of ionized nitrogen gas extending at least 68,000 miles (109,000 km) beyond Pluto. This “plasma tail” is evidence that the atmosphere is being stripped by the solar wind and lost to space. The rate of escape will be nailed down when more data come down to Earth next month, but team members offered an estimate today.
“What we think it is, based on models and a pretty good guess, is about 500 tons per hour of material that is escaping,” said Fran Bagenal of the University of Colorado Boulder, who leads New Horizons’ particles and plasma team.
For comparison, Mars is losing about 1 ton of its atmosphere per hour, Bagenal added.
Mission team members also released today the first-ever good photo of the small Pluto satellite Nix. (Pluto has five known moons: Charon, which is half as wide as the dwarf planet itself, and Nix, Hydra, Kerberos and Styx, all of which are tiny.)
The new image reveals that Nix is about 25 miles (40 km) wide, and intermediate in reflectivity between Pluto and Charon, researchers said. (Charon is considerably more reflective than Pluto.)
All of this new information is but a trickle compared to the flood to come, however. New Horizons has beamed home less than 2 percent of the data it collected during its historic flyby, and NASA has yet to release any images taken at or near closest approach, when the probe was just 7,800 miles (12,500 km) from Pluto’s surface.
Scientific American for more