New Pluto Moon Hints at Perilous Journey for Spacecraft

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The discovery of another moon around Pluto is exciting news for planetary science, but it's also likely causing some anxiety for the team in charge of New Horizons, a spacecraft set to be the first probe ever to visit the dwarf planet.

On Wednesday (July 11), researchers using NASA's Hubble Space Telescope announced the detection of P5, a tiny moon measuring just 6 to 15 miles (10 to 24 kilometers) across. P5 brings Pluto's known satellite tally to five, and it comes just a year after Hubble spotted moon number four, the similarly diminutive P4.

These two recent discoveries show that the Pluto system is more crowded than scientists had thought. So NASA's New Horizons spacecraft, which is due to fly by the dwarf planet in 2015, may have to watch its step.

"We're finding more and more, so our concern about hazards is going up," New Horizons principal investigator Alan Stern, of the Southwest Research Institute in Boulder, Colo., told SPACE.com.

The concern is not necessarily that New Horizons, which launched in 2006, will slam into a Pluto moon that has thus far eluded detection. The probe is traveling so fast that a particle the size of a BB could destroy it, so researchers are worried about the broad debris field that Pluto's moons may have spawned.

"Every new satellite is a debris producer," Stern said. When these moons suffer impacts, he explained, "the ejecta goes into orbit around Pluto, and so the more satellites, the more concern we have."

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