What secrets might lie in wait? [The Greatest Mysteries of the Planets]
For one thing, the dwarf planet could possess a set of everyone's favorite cosmic accessories. "It's a very distinct possibility and the theoretical arguments are very strong that Pluto has rings that come and go with time," Stern told Life's Little Mysteries.
Space rocks and other debris litter the Kuiper belt, where Pluto resides, and they probably pepper the icy world and its moons. "The moons are being hit all the time, and the ejecta [collision debris] escapes, making a ring," Stern said. "And then radiation and gravity depletes the ring through erosion."
Computer models of this cycle suggest that all the dwarf planet's rings sometimes get eroded before a new one forms. "When you model that on a computer there is randomness to [the spacing of the collision events], and so the rings come and go according to these models," he said.
Beneath those fleeting rings, and beneath Pluto's thin, nitrogen-rich atmosphere, it's anyone's guess how the surface will appear when viewed up close. In Hubble images, the dwarf planet's mottled façade varies between extremes of charcoal black, dark orange and white. What materials compose these assorted regions? And do they give rise to cold-liquid-spewing cryovolcanoes or geysers? The surface's geochemistry might even hint at a giant underground ocean. [The True Stories of 5 Mystery Planets]
More data is also needed to clarify how Pluto wound up in its frigid Kuiper belt domain. Astronomers think it and its neighbors formed from the same disk of material around the sun that coalesced into the other major bodies in the solar system. But at some point early on, a planetary collision probably sent Pluto ricocheting far beyond the rest, forever to carry the mark of this fateful encounter in the form of its strange, oval path around the sun, which lies off the plane of the other planetary orbits.