Bruce Murray Space Image Library

Hydra viewed by New Horizons

Hydra viewed by New Horizons
Hydra viewed by New Horizons

Since its discovery in 2005, Pluto's moon Hydra has been known only as a fuzzy dot of uncertain shape, size, and reflectivity. Imaging during New Horizons' historic transit of the Pluto-Charon system definitively resolved these fundamental properties of Pluto's outermost moon. Long Range Reconnaissance Imager (LORRI) observations from a distance of approximately 640,000 kilometers revealed an irregularly shaped body characterized by significant brightness variations over the surface. With a resolution of 3 kilometers per pixel, the LORRI image shows the tiny potato-shaped moon measures 43 kilometers by 33 kilometers.

Like that of Pluto's largest moon Charon, Hydra's surface is probably covered with water ice. Observed within Hydra's bright regions is a darker circular structure approximately 10 kilometers in diameter. Hydra's reflectivity is intermediate between that of Pluto and Charon.


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