BOB HIRSHON (host):
The crazy, mixed up Pluto family. I’m Bob Hirshon and this is Science Update.
When the New Horizons spacecraft flew by Pluto, its companion world, Charon and four much smaller moons, they assumed it was an orderly little family, rotating and orbiting slowly along the same plane, like the Earth and Moon.
HAL WEAVER (Applied Physics Laboratory, Johns Hopkins University):
It’s not like that at all; it’s almost like the opposite. These things are like spinning tops, the directions of their poles are almost completely, almost ninety degrees away from the direction of Pluto and Charon’s pole, which are aligned with each other.
That’s planetary scientist Hal Weaver of the Johns Hopkins University Applied Physics Lab. In the journal Science, he and his colleagues report that these eccentric orbits and rapid spin rates suggest a violent history in which two Pluto-sized objects collided, spawning a ring of debris that coalesced into the four smaller worlds. I’m Bob Hirshon, for AAAS, the science society.