Pluto's moon Hydra has pristine water ice

​Washington: NASA's New Horizons spacecraft has sent first-ever data about Pluto's four moons that shows that the surface of Hydra is dominated by nearly pristine water ice.

The Hydra spectrum is similar to that of Pluto's largest moon, Charon, which is also dominated by crystalline water ice. But Hydra's water-ice absorption bands are even deeper than Charon's, suggesting that ice grains on Hydra's surface are larger or reflect more light at certain angles than the grains on Charon.

Pluto's outermost small moon, Hydra is thought to have formed in an icy debris disk some four billion years ago. Mission scientists are investigating why Hydra's ice seems to be cleaner than Charon's.