As NASA looks toward the New Horizons probe‘s July 2015 rendezvous with dwarf planet Pluto and its five known moons, they are also reviewing Voyager 2 data collected on the 1989 flyby of Neptune’s moon Triton, seen here in this restored and enhanced historical footage from JPL:
Triton has a similar “radius, density, temperature and chemical composition” to Pluto, a few of the clues that have lead planetary scientists to believe that Triton is a captured KBO (Kuiper Belt Object). From The New York Times:
Triton, Neptune’s largest moon and one of the largest in the solar system, is the only one that goes around its planet backward, in the opposite direction of Neptune’s rotation – retrograde, in astronomical lingo. Which means it couldn’t have formed out of the swirling blob of gas and dust from which Neptune presumably condensed back at the dawn of the solar system.
Astronomers have concluded, therefore, that Triton is a stranger from outside Neptune’s system; the moon was kidnapped, they theorize, from the Kuiper Belt, a vast ring of icy debris left over from the formation of the solar system.
And by the way…
More videos about the Voyager Mission and Brian Cox’s Favorite Wonder: Saturn’s moon Titan.
It was Pluto’s similarity to Kuiper Belt objects, including an egg-shaped orbit that sometimes took it inside Neptune’s orbit, that helped seal its demise as a planet.