NASA
A pair of small moons orbiting Pluto named Nix and Hydra were discovered by NASA's Hubble Space Telescope in 2005. The two moons are roughly 5,000 times fainter than Pluto and are about two to three times farther from Pluto than its large moon, Charon, which was discovered in 1978.
By
updated 11/29/2011 5:14:40 PM ET 2011-11-29T22:14:40

When NASA's New Horizons spacecraft reaches Pluto in July 2015, it may find the region more hazardous than anticipated. The discovery of several moons around Pluto — and the potential for more — increase the risks during the probe's flyby.

The main problem is debris. The small moons are under constant bombardment from nearby space rocks called Kuiper Belt objects, but the moons' low gravity prevents them from holding on to chunks of dirt and rock that fly into the air when hit. The debris instead finds itself caught in orbit around Pluto, where it could pose a serious threat to New Horizons.

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An artist's concept of the New Horizons spacecraft as it visits Pluto in 2015. Instruments will map Pluto and its moon, Charon, providing detail not only on the surface of the dwarf planet, but also about its shape, which could reveal whether or not an ocean lies beneath the ice.

"The most likely problem we would encounter is to be hit by something that is large enough to instantly destroy the spacecraft," New Horizons principal investigator Alan Stern, of the Southwest Research Institute in San Antonio, Texas, told Space.com.

Though cameras on the New Horizons probe will begin observing the Pluto system several months before its closest approach, they won't be able to detect the fast-flying milligram-size particles that could spell instant death if they collide with the vehicle.

New moons on the rise
Pluto's first known moon, Charon, was discovered in 1978, nearly 50 years after the dwarf planet was found. The Hubble Space Telescope discovered the next two of Pluto's moons in 2005, only two and a half months before New Horizons was launched.

In July of this year, a fourth moon of Pluto was located, and there are hints that two more might exist.

With three of Pluto's four moons having been discovered in the last five years, scientists have a hunch there are likely more still hidden.

Due to these new additions, a group of experts recently convened to analyze the hazards New Horizons might face. After determining the threat was real, they discussed how to avoid it.

A harder look at the challenge could make a significant difference, scientists say. Continuing to study the system with the Hubble Space Telescope, as well as several ground-based telescopes, could help reveal other hidden moons and their orbits well before New Horizons arrives.

Hunting hidden moons
But searching doesn't necessarily mean success.

"If there are moons too small, meaning too faint, then we won't find them," Stern said.

With that in mind, the group also determined the need for a good "safe haven bailout trajectory," or SHBOT — an orbit that New Horizons could shift into that would keep it away from the most likely danger zones.

The best route would zip through Charon's orbit, but on the opposite side of the planet from the moon. The large body constantly clears debris from its path, creating a safe route for New Horizons to pass through.

This strategy works best if the debris remains in a plane, similar to Saturn's rings. If, however, it orbits Pluto in a cloud, the danger is heightened.

If New Horizons encounters dirt and dust from the moons, it could put an abrupt end to the first mission to Pluto.

"There is no wounded here — only dead or alive," Stern said.

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Gallery: The new solar system

Get the facts about dwarfs, giants, terrestrials and other denizens of our planetary realm.

Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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