"In the NFL, something that behaves like Pluto's football-shaped moons might be called a wobbly duck. NASA simply calls them astonishing."

"Instead of steadily rotating through their orbits, two of Pluto's moons "wobble unpredictably," the space agency says, citing new analysis of data from the Hubble Space Telescope."

"The two moons, Hydra and Nix, are the largest of the four moons that move around Pluto and Charon — the 'double planet' that is the destination of next month's visit by NASA's New Horizons spacecraft."

"New Horizons is expected to provide new details of Pluto, which has never been photographed in crisp detail. For now, scientists are going over the new Hubble analysis."