That suggests, the space agency noted, the region may still be geologically active today.
"These very small planets can be very active after a long time," said Stern. "It's going to send geophysicists back to the drawing board to figure out how they do that."
Charon, the largest of Pluto's known moons, also shows signs of geological activity.
A 600-mile-long area of cliffs and troughs is leading scientists to believe there has been a widespread fracturing of Charon's crust, which could very well be the result of internal geological processes.
NASA researchers noted that this is just the first taste of the information that they expect to come pouring back from New Horizons about Pluto and its system.
The space agency plans to have another news conference on Friday to offer up more information, including measurements of Pluto's atmosphere and possibly information on the dwarf planet's four other moons -- Nix, Hydra, Styx and Kerberos.
New Horizons, which was designed, built and operated by Johns Hopkins University, uses seven instruments, including an infrared imager; an ultraviolet spectrometer that analyzes Pluto's atmosphere; and a telescopic camera.
The new images are expected to be 10 times higher in resolution than previous images the probe sent back as it approached Pluto.
On Tuesday, NASA administrator Charles Bolden called New Horizons' flyby of Pluto a historic accomplishment, noting that with this mission NASA spacecraft have visited every planet in the solar system.
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