Pluto continues to surprise, say scientists who've announced the latest findings of the New Horizons mission to the dwarf planet, including flowing ices and a hazy atmosphere reaching higher than had been predicted.
At one edge of a heart-shaped area that has intrigued astronomers since the New Horizons probe sent back the first clear images of the planet's surface, they've seen evidence of exotic ices flowing across Pluto's surface. That strongly suggests recent geologic activity, something that had not been expected, mission scientists said.
"We've only seen surfaces like this on active worlds like Earth and Mars," says New Horizons co-investigator John Spencer of the Southwest Research Institute in Boulder, Colorado. "I'm really smiling."
In the western half of the heart-shaped region known as the Tombaugh Regio — named for Clyde Tombaugh, who discovered Pluto in 1930 — smooth sheets of ice appear to have flowed and may still be moving, much as glaciers on Earth slowly move.
The ices are likely made up of nitrogen, methane and carbon dioxide, NASA scientists say.
"At Pluto's temperatures of minus-390 degrees Fahrenheit, these ices can flow like a glacier," says Bill McKinnon of Washington University in St. Louis, deputy leader of the New Horizons Geology, Geophysics and Imaging team.
Other images of the dwarf planet have scientists looking carefully at what's going on above Pluto's surface.
As the New Horizons probe sped away after its close flyby on July 14, it captured a dramatic image of Pluto's atmosphere, backlit by the distant sun.
It shows hazy layers of atmosphere extending much higher above the planet than had been predicted, NASA says.
Within the atmosphere that reaches to 80 miles above the surface are two distinct hazy layers, one at 30 miles high and another at around 50 miles.
"My jaw was on the ground when I saw this first image of an alien atmosphere in the Kuiper Belt," says New Horizons Principal Investigator Alan Stern at the Boulder institute. "It reminds us that exploration brings us more than just incredible discoveries — it brings incredible beauty."
It is thought that the hazes form when ultraviolet sunlight breaks apart methane gas in Pluto's atmosphere, creating more complex hydrocarbon gases that then fall to the lower, colder parts of the atmosphere, condensing as ice particles to form the hazy layers.
With just 5 percent of the data gathered by New Horizons' flyby sent back to Earth so far — the rest is still on the probe awaiting transmission — scientists say they expect many more exciting discoveries to come.
"It's really turning out to be just a scientific wonderland," says Stern.
