Pluto’s “heart” contains shifting glaciers of frozen nitrogen, methane and carbon monoxide, and its atmosphere is both deeper and disappearing more rapidly than scientists predicted, New Horizons mission leaders said Friday.
Close-up images of Tombaugh Regio, the large heart-shaped formation near Pluto’s equator, show the smooth, brightly colored area flowing around mountains and filling craters. The geology resembles that of glaciers on Earth.
Observations of Pluto’s atmosphere, meanwhile, show a haze extending above the surface,. And air pressure on the surface is dropping dramatically as the dwarf planet moves into the cold.
The revelations are some of the first to come from New Horizons’ historic encounter with Pluto on July 14, a mission managed by the Johns Hopkins Applied Physics Laboratory.
Most of the data gathered during the flyby is still on the spacecraft, but with about 5 percent of it on the ground, it is already proving illuminating, the scientists said.
“It’s really turning out to be just a scientific wonderland,” said Alan Stern, the mission’s principal investigator and a researcher at the Southwest Research Institute in Boulder, Colo.
The scientists believe that heat may be driving some of the motion of the ice that covers the western half of Tombaugh Regio, causing it to rise and fall beneath the surface. Even at Pluto’s surface temperatures of about 380 degrees below zero, the elements prevalent in the ice are relatively soft, said Bill McKinnon, deputy leader of the mission’s geology team.
McKinnon pointed out “a pattern that indicates the flow of viscous ice” that appears to move “just like glacial flow on the Earth.” While water ice on Pluto freezes to the point of immovable bedrock, nitrogen and methane ice are “soft and malleable,” he said.
McKinnon said the team’s leading theory for the formation of the plains and ice flows is “heat leaking out of the interior of Pluto” — an internal energy driving change on its surface. He said that there may be an internal ocean, for example, emitting heat from below the surface and nitrogen ice.
Researcher Mike Summers said the newest image, which shows a band of sunlight dissolving into a faint haze around Pluto, forces scientists to “basically start from scratch” in how they think about its atmosphere.
“This is the image that almost brought tears to the eyes of the atmospheric scientists,” he said.
The haze of small particles extends at least 100 miles above the surface, he said, five times higher than predicted and a profound mystery for now.
Researcher Cathy Olkin said Pluto’s diverse regions and colorings could in part be explained by its long and eccentric orbit: A Plutonian year around the sun takes 248 Earth years, and its north pole is tilted to a 120-degree angle.
New Horizons data show its atmosphere’s mass has dropped significantly relative to estimates from two years ago, likely because Pluto is moving away from the sun in its 248-year orbit.
Air pressure on its surface is 1/100-thousandth that of the pressure on the surface of Earth, scientists said.