its formation. Rotation Hydra is not tidally locked and rotates chaotically; its rotational period and axial tilt vary quickly over astronomical timescales, to the point that its rotational axis regularly flips over. Hydra's chaotic tumbling is largely caused by the varying gravitational influences of Pluto and Charon as they orbit around their barycenter. Hydra's chaotic tumbling is also strengthened by its irregular shape, which creates torques that act on the object. At the time of the New Horizons flyby of Pluto and its moons, Hydra's rotation period was approximately 10 hours and its rotational axis was tilted about 110 degrees to its orbit — it was rotating sideways at the time of the New Horizons flyby. Hydra rotates relatively quickly compared to the rest of Pluto's moons, which all have rotation periods greater than one day. This rapid rotation of Hydra is common among the rotation periods of most Kuiper belt objects. Hydra's surface material could get ejected due to centrifugal forces if it were rotating at a faster rate. Orbit Hydra orbits the Pluto-Charon barycenter at a distance of . Hydra is the outermost moon of Pluto, orbiting beyond Kerberos. Similarly to all of Pluto's moons, Hydra's orbit is nearly circular and is coplanar to Charon's orbit; all of Pluto's moons have very low orbital inclinations to Pluto's equator. The nearly circular and coplanar orbits of Pluto's moons suggest that they may have gone through tidal evolutions since their formation. At the time of the formation of Pluto's smaller moons, Hydra may have had a more eccentric orbit around the Pluto-Charon barycenter. The present circular orbit of Hydra may have been caused by Charon's tidal damping of the eccentricity of Hydra's orbit, through tidal interactions. The mutual tidal interactions of Charon on Hydra's orbit would cause Hydra to transfer its orbital eccentricity to Charon, thus causing the orbit of Hydra to gradually become more circular over time. Hydra has an orbital period of approximately 38.2 days and is resonant with other moons of Pluto. Hydra is in a 2:3 orbital resonance with Nix, and a 6:11 resonance with Styx (the ratios represent numbers of orbits completed per unit time; the period ratios are the inverses). As a result of this "Laplace-like" 3-body resonance, it has conjunctions with Styx and Nix in a 5:3 ratio. Hydra's orbit is close to a 1:6 orbital resonance with Charon, with a timing discrepancy