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Pluto’s moon Hydra has icy surface; New Horizons team wins awards


Hydra as seen by New Horizons during the spacecraft’s historic flyby in July 2015. Photo Credit: Johns Hopkins University Applied Physics / NASA

The first New Horizons data on the Pluto system’s four small moons reveals that outermost moon, Hydra, has a surface composed mostly of pristine water ice. Returned nearly ten months after the spacecraft’s historic flyby, the findings came just as the New Horizons team was recognized publicly with several prestigious awards.

The images of Hydra, which has a highly reflective surface, were taken at a distance of about 150,000 miles (240,000 kilometers) by the spacecraft’s Ralph / Linear Etalon Imaging Spectral Array (LEISA) on July 14, 2015.


Image Credit: Johns Hopkins University Applied Physics Laboratory / NASA

Infrared spectra of Hydra are very similar to those of Charon, the system’s largest moon, which is also covered in crystalline water-ice.

Hydra’s water ice absorption bands are deeper than Charon’s. Mission scientists surmise that this is due to Hydra’s water ice grains being larger than those on Charon or the fact they reflect light from different angles than do the same grains on Charon.

The water ice on Hydra is cleaner and less contaminated by the darker materials found in Charon’s surface water ice. Scientists are researching the reasons for this and posit they may be the result of the system’s formation in a giant impact four billion years ago.

Like the Earth-Moon system, the Pluto-Charon binary, along with its moons, was created when a large Kuiper Belt Object, possibly of dwarf planet size, collided with proto-Pluto.

That impact produced an icy disk of debris composed largely of materials stripped from the water-rich mantles of both proto-Pluto and the impacting object. As the objects in the system coalesced, water ice from the debris disk settled on their surfaces.

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

Mission scientists are awaiting spectral data from the system’s other small moons, which they plan to compare with the findings at Hydra.

New Horizons Team Awards

New Horizons mission team members display the National Air and Space Museum’s Current Achievement Trophy, awarded on April 5, 2016. Photo and Caption Credit: Eric Long / National Air and Space Museum

The steady stream of data is not the only good news being received by the New Horizons mission. Last month, the mission team was awarded the National Air and Space Museum Trophy for Current Achievement, a prestigious annual award recognizing a significant scientific or technological achievement.

Principal Investigator Alan Stern noted the significance of the first exploration of the Kuiper Belt and its cost-effective execution.

“In completing the first reconnaissance of the Solar System, the flyby of Pluto was not the end of something, but instead, I believe, a new beginning,” he said at the awards ceremony on April 5 at the Washington, DC, museum. “We showed how much the public craves bold exploration, and we showed just how much exploration can teach us about nature when we visit new places with capabilities never before brought to bear.”

Just a week later, the New Horizons team was awarded the 2016 John L. “Jack” Swigert, Jr Award for Space Exploration by the Space Foundation in Colorado Springs, Colorado.

Named for the late Apollo 13 astronaut Jack Swigert, Jr of Colorado, the award is given annually to an individual or organization that made the most successful accomplishment in space exploration during the previous year.

“The world fell in love with Pluto’s heart, and the mission brought the curiosity of space exploration to the forefront of everyone’s minds,” said Space Foundation chief executive Elliot Pulham. “Data collection continues into 2016, making the Pluto / New Horizons mission not only a success but [also] an inspiration.”

The mission was honored for the third time in April with the Edison Award for Science, an international prize named for the late inventor Thomas Edison, recognizing excellence in a variety of areas, including human-centered design and innovation, and the development and marketing of new products and services.

New Horizons received the highest level of recognition, a gold award, in the category of space exploration.

The mission team’s public outreach continues with a May 6 blog post by Veronica Bray, a planetary scientist at the Lunar and Planetary Laboratory in Tucson, Arizona.

Titled A Picture of Pluto is Worth a Thousand Words, the blog entry discusses how Pluto’s composition can be deduced from photos taken by the spacecraft’s cameras.

Bray’s specialty is the study of impact craters, whose features can reveal much about an object’s physical properties.

Video courtesy of the National Air and Space Museum




Laurel Kornfeld is an amateur astronomer and freelance writer from Highland Park, NJ, who enjoys writing about astronomy and planetary science. She studied journalism at Douglass College, Rutgers University, and earned a Graduate Certificate of Science from Swinburne University’s Astronomy Online program. Her writings have been published online in The Atlantic, Astronomy magazine’s guest blog section, the UK Space Conference, the 2009 IAU General Assembly newspaper, The Space Reporter, and newsletters of various astronomy clubs. She is a member of the Cranford, NJ-based Amateur Astronomers, Inc. Especially interested in the outer solar system, Laurel gave a brief presentation at the 2008 Great Planet Debate held at the Johns Hopkins University Applied Physics Lab in Laurel, MD.

Reader Comments

Ed Christiansen

So proud of what we set in motion 10 years ago has done so well. Ed Christiansen, Atlas Launch Conductor for Pluto New Horizons

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