The data show the surface of Hydra is dominated by nearly pristine water ice – confirming New Horizons images showing Hydra’s highly reflective surface.
Hydra is the outermost known moon of Pluto and it was discovered in June 2005. The moon is thought to have formed in an icy debris disc produced when water-rich mantles were stripped from the two bodies that collided to form the Pluto-Charon binary some four billion years ago.
Hydra’s deep water bands and high reflectance imply relatively little contamination.
“Perhaps micrometeorite impacts continually refresh the surface of Hydra by blasting off contaminants,” said Simon Porter, a New Horizons science team member from Southwest Research Institute in Colorado.
The New Horizons science team is looking forward to obtaining similar spectra of Pluto’s other small moons, for comparison to Hydra.