spaceSpace and Physics

Pluto's Smooth Ice Field Possibly Explained By Manhattan-Sized Asteroid Impact


Jonathan O'Callaghan

Senior Staff Writer

514 Pluto's Smooth Ice Field Possibly Explained By Manhattan-Sized Asteroid Impact
Why is Sputnik Planum (to the right in this image) so smooth? NASA/JHUAPL/SwRI

Another week, another cavalcade of new data from Pluto. And among new images returned by New Horizons, a theory has been proposed for one of the dwarf planet’s strange ice fields – a Manhattan-sized asteroid striking the surface.

Speaking at the 227th meeting of the American Astronomical Society in Florida, New Horizons principal investigator Alan Stern explained the new theory for Sputnik Planum, a large crater-free ice field on Pluto that has puzzled scientists. Its smooth appearance suggests it has seen significant changes, geological or otherwise, in the past hundred million years.


“We believe [Sputnik Planum] is a large impact basin,” Stern said, reported Gizmodo, formed by an asteroid 10 kilometers (6 miles) wide. This could have created the depressed, smooth terrain we see today. Such is its size that Stern even postulated that the whole field may have shifted over time to its current position near the equator.

Chaotic mountain ranges surrounding the ice field could also have been caused by the giant impact. It's not clear when it would have occurred though, but it is just one theory for explaining how this strange feature on Pluto formed.

Aside from this intriguing theory, NASA has also released new images of Pluto. One returned on Christmas Eve, from New Horizons’ Long Range Reconnaissance Imager (LORRI), shows an “X” feature within Sputnik Planum. Scientists suggest this may be the result of nitrogen ices being warmed by heat from within Pluto, which rise to the surface as blobs and sink again.

The "X"-shaped feature can be seen here. NASA/JHUAPL/SwRI


“This part of Pluto is acting like a lava lamp, if you can imagine a lava lamp as wide as, and even deeper than, the Hudson Bay,” said William McKinnon, deputy lead of the New Horizons Geology, Geophysics and Imaging team, in the statement.

Pictures from LORRI have also helped scientists examine bright methane ices on the rims of craters on Pluto. These contain dark red tholins, which are small soot-like particles that have been generated from the reaction of methane and nitrogen in the atmosphere, partially giving Pluto its red tinge.

Where the material is thickest and the surface is smooth, the material seems to have flowed, possibly with the help of ice or even being blown around by winds on Pluto.

Pluto's red color comes from dark red tholins. NASA/JHUAPL/SwRI


All of this combined shows there is much we still do not understand about Pluto. What we do know is that it is far more fascinating than anyone imagined, and likely still geologically active – a very surprising discovery.


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