Did A ‘Big Whack’ Create All Of Pluto’s Moons?
“All five worlds are inclined at less than one degree to Pluto’s equator, indicating that there was no gravitational capture. While Pluto is reddish in color, the lack of volatiles is seen in all five moons, meaning that whatever impact likely created the moons also prevented these same moons from hanging onto the lightest elements and molecules. And finally, close-up studies of the four small moons — Styx, Nix, Kerberos, and Hydra — all indicate that these bodies coalesced out of multiple, smaller bodies that later became gravitationally bound.”
When the Hubble Space Telescope discovered additional moons of Pluto, beyond Charon, it was speculated that New Horizons might find more. After all, objects more than ten times as far away as Hydra, Pluto’s outermost moon, would still be in stable orbits. Yet, with five inner moons and nothing beyond, not even diffuse rings, the spacecraft came up empty. This isn’t a disappointment, though! Instead, New Horizons’ detailed observations of all five of Pluto’s moons point towards a tremendous picture: that the entire Plutonian system owes its origin to a massive, ancient collision. The debris kicked up created the five grey moons, in stark contrast to the reddish color of Pluto, in a near-perfect 1:3:4:5:6 resonance.