From possible ice volcanoes to twirling moons, NASA's New Horizons science team is busy analysing more than 50 exciting discoveries about Pluto that the probe has revealed so far.
"The New Horizons mission has taken what we thought we knew about Pluto and turned it upside down," said Jim Green, director of planetary science at NASA headquarters in Washington, DC.
For one such discovery, New Horizons geologists combined images of Pluto's surface to make 3D maps that indicate two of Pluto's most distinctive mountains could be cryovolcanoes -- ice volcanoes that may have been active in the recent geological past.
"It's hard to imagine how rapidly our view of Pluto and its moons are evolving as new data stream in each week. As the discoveries pour in from those data, Pluto is becoming a star of the solar system," said mission principal investigator Alan Stern.
The two cryovolcano candidates are large features measuring tens of miles or kilometers across and several miles or kilometers high.
"These are big mountains with a large hole in their summit, and on Earth that generally means one thing -- a volcano," added Oliver White, New Horizons postdoctoral researcher.
If they are volcanic, then the summit depression would likely have formed via collapse as material is erupted from underneath.
Pluto's surface varies in age -- from ancient to intermediate to relatively young -- according to another new finding from New Horizons.
The crater counts of surface areas on Pluto indicate that it has surface regions dating to just after the formation of the planets of our solar system, about four billion years ago.
But there also is a vast area that was, in geological terms, born yesterday -- meaning it may have formed within the past 10 million years.
This area, informally named Sputnik Planum, appears on the left side of Pluto's "heart" and is completely crater-free in all images received, so far.
New data from crater counts reveal the presence of intermediate, or "middle-aged", terrains on Pluto as well.
This suggests Sputnik Planum is not an anomaly -- that Pluto has been geologically active throughout much of its more than 4-billion-year history.
"We've mapped more than a thousand craters on Pluto, which vary greatly in size and appearance," said Kelsi Singer from Southwest Research Institute (SwRI) in Boulder, Colorado.
Crater counts are giving the New Horizons team insight into the structure of the Kuiper Belt itself.
The dearth of smaller craters across Pluto and its large moon Charon indicate the Kuiper Belt, which is an unexplored outer region of our solar system, likely had fewer smaller objects than some models had predicted.
New Horizons' next potential target is the 40-50 km wide Kuiper Belt Object (KBO) named 2014 MU69 which may offer the first detailed look at just such a pristine, ancient building block of the solar system.
The New Horizons mission also is shedding new light on Pluto's fascinating system of moons, and their unusual properties.
For example, nearly every other moon in the solar system -- including Earth's moon -- is in synchronous rotation, keeping one face toward the planet. This is not the case for Pluto's small moons.
Images of Pluto's four smallest satellites also indicate several of them could be the results of mergers of two or more moons.
The findings were presented at the meeting of the American Astronomical Society's Division for Planetary Sciences in National Harbor, Maryland, recently.
