Pluto's Moon Coated in Nearly Pure Water Ice

Discovered in June 2005, Pluto’s outermost moon Hydra is thought to have formed four billion years ago during a massive impact event that created Pluto and Charon.

Despite its age, this 31-mile-wide moon appeared remarkably clean and bright in New Horizons images during the spacecraft’s historic close pass through the Pluto system in July 2015.

Scientists’ initial speculation was proved right when data from the spacecraft was analyzed and revealed that Hydra, like its name, is covered in nearly pure water ice.

Measured with the Linear Etalon Imaging Spectral Array (LEISA) on New Horizons’ Ralph instrument, the spectral signature of water ice on Hydra is even stronger than that seen on Pluto’s much larger satellite Charon, indicating a surface coated with bigger ice particles and less dusty, dark material.

Spectral data gathered by New Horizons shows Hydra to be coated in a much more pure ice material than the larger Charon.

“Perhaps micrometeorite impacts continually refresh the surface of Hydra by blasting off contaminants,” said Simon Porter, a New Horizons science team member from the Southwest Research Institute (SwRI) in Boulder, Colorado. “This process would have been ineffective on the much larger Charon, whose much stronger gravity retains any debris created by these impacts.”

Read more at Discovery News