Pluto’s outermost moon, Hydra, was only discovered in June 2005, but now scientists have confirmed that it is covered in almost pure water ice.
It is thought that Hydra formed after a massive impact event around 4 billion years ago which also led to the formation of Pluto and Charon. Hydra is only 31 miles wide but it appeared clean and bright in images beamed back to Earth by NASA’s New Horizons spacecraft, writes Ian O’Neill for Discovery.
Hydra piques the interest of scientists
New Horizons made a historic close pass by Pluto in July 2015. Scientists were intrigued by the brightness of Hydra, and speculated that the small moon could be covered in water ice.
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Now data from the NASA spacecraft has been analyzed, confirming that Hydra is covered by almost pure water ice. The Linear Etalon Imaging Spectral Array (LEISA) on New Horizons’ Ralph instrument was used to measure the spectral signature of water ice on Hydra, which is even stronger than that seen on Pluto’s larger moon Charon.
This means that Hydra is covered in larger ice particles with less dusty material.
New Horizons provides valuable data to scientists
“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.”
Hydra appeared only as a small speck in even the best images from the Hubble space telescope. New Horizons was able to drastically improve our knowledge of Pluto and its moons during a historic fly by.
The NASA spacecraft revealed that Hydra is an irregular shaped moon that looks “like the state of Michigan.” It has at least two large craters and the upper region is slightly darker than the lower, which would suggest that the surface composition is different.
Spacecraft pushing human knowledge
“Before last week, Hydra was just a faint point of light, so it’s a surreal experience to see it become an actual place, as we see its shape and spot recognizable features on its surface for the first time,” said Ted Stryk, mission science collaborator from Roane State Community College in Tennessee at the time of the fly by.
Pluto is orbited by Charon, Nix, Hydra and two more moons called Kerberos and Styx. The latter pair were discovered by Hubble in 2011 and 2012 respectively.
New Horizons was able to beam back more information on Pluto and its satellites, allowing scientists to better understand this area of the Kuiper belt. Mission scientists are looking forward to receiving information about the other small moons so that they can compare them to Hydra and Charon.
Space exploration continues to advance at a considerable pace, and public interest in the subject continues to be high. NASA has contributed to a wave of space fever with its masterful use of social media, but the fact is that there are some remarkable advances being made.
One such example is the successful testing of reusable rockets by SpaceX and Blue Origin, which means that space travel should become far less expensive than before. This cost reduction means that manned missions to Mars are moving closer to becoming a reality, with NASA projecting that such a mission could take place in the 2030s.