New Horizons Investigation of Pluto's Small Satellites

Abstract:

Pluto has four small moons: Styx, Nix, Kerberos, and Hydra, in order
of their distance from Pluto. All were discovered using the
Hubble Space Telescope (HST): Nix and Hydra in 2005 (1), Kerberos in
2011 (2), and Styx in 2012 (3).

The New Horizons (NH) mission has provided the first opportunity to
perform spatially resolved imaging and spectroscopic measurements of
Pluto’s small moons, thereby giving direct measurements of their
sizes, shapes, surface albedo and color variations, surface composition,
and snapshots of their rotational states. In addition, an extensive and
systematic set of unresolved panchromatic brightness measurements of the
small moons over a six month period (January-July 2015) was obtained by
NH, which provides additional information on their shapes and more precise
information on their rotational states.

Here we review the results obtained to date by NH on the properties
of Pluto's small moons. We compare those results to the properties
of other small bodies in the solar system, and we address how the
new NH results bear on the origin and evolution of the Pluto system.

(1) H. A. Weaver et al., Discovery of two new satellites of Pluto Nature 439, 943 (2006).
(2) M. R. Showalter et al., New satellite of (134340) Pluto: S/2011 (134340), IAU Circ. 9221 (2011).
(3) M. R. Showalter et al., New satellite of (134340) Pluto: S/2011 (134340), IAU Circ. 9253 (2012).