Pluto’s Moons Orbit Planet in Very Odd Ways

Video Caption: Most inner moons in the solar system keep one face pointed toward their central planet; this animation shows that certainly isn’t the case with the small moons of Pluto, which behave like spinning tops. Pluto is shown at center with, in order, from smaller to wider orbit: Charon, Styx, Nix, Kerberos, Hydra.

NATIONAL HARBOR, Md. (NASA PR) — The New Horizons mission is shedding new light on Pluto’s fascinating system of moons, and their unusual properties. For example, nearly every other moon in the solar system — including Earth’s moon — is in synchronous rotation, keeping one face toward the planet. This is not the case for Pluto’s small moons.

Pluto’s small lunar satellites are spinning much faster, with Hydra — its most distant moon — rotating an unprecedented 89 times during a single lap around the planet. Scientists believe these spin rates may be variable because Charon exerts a strong torque that prevents each small moon from settling down into synchronous rotation.

Another oddity of Pluto’s moons: scientists expected the satellites would wobble, but not to such a degree.

Pluto’s moons behave like spinning tops,” said co-investigator Mark Showalter of the SETI Institute in Mountain View, California.

Images of Pluto’s four smallest satellites also indicate several of them could be the results of mergers of two or more moons.

Data from NASA's New Horizons mission indicates that at least two -- and possibly all four -- of Pluto’s small moons may be the result of mergers between still smaller moons. If this discovery is borne out with further analysis, it could provide important new clues to the formation of the Pluto system. (Credits: NASA/JHUAPL/SwRI)
Data from NASA’s New Horizons mission indicates that at least two — and possibly all four — of Pluto’s small moons may be the result of mergers between still smaller moons. If this discovery is borne out with further analysis, it could provide important new clues to the formation of the Pluto system. (Credits: NASA/JHUAPL/SwRI)

“We suspect from this that Pluto had more moons in the past, in the aftermath of the big impact that also created Charon,” said Showalter.

To view more images and graphics being presented by New Horizons scientists at the 47th Annual Meeting of the American Astronomical Society’s Division for Planetary Sciences, visit:

http://pluto.jhuapl.edu/News-Center/Press-Conferences/November-9-2015.php

For more information on NASA’s New Horizons mission, including fact sheets, videos and images, visit:

http://www.nasa.gov/newhorizons