There's a comet headed toward Mars and the last thing the National Aeronautics and Space Administration wants is any of its robot orbiters circling the Red Planet to end up the victim of a comet-particle impact.

That's why America's top space agency is ordering the three Earth-made probes expected to be on hand during the close flyby of Comet C/2013 A1 Siding Spring Oct. 19 to steer clear of the general vicinity, according to a NASA news release.

Calculations suggest the comet's nucleus will miss the plante by about 82,000 miles (132,000 kilometers), while the material it sheds, forming the much-more hazardous wake, or tail, will hurtle past at about 35 miles -- 56 kilometers -- per second, relative to Mars and the orbiting spacecraft.

At that speed, even the smallest particle, which scientists suspect could be no more than one-half of a millimeter, or a fiftieth of an inch, could wreck havoc on a Terran spacecraft.

"Three expert teams have modeled this comet for NASA and provided forecasts for its flyby of Mars," Rich Zurek, chief scientist for the Mars Exploration Program at NASA's Jet Propulsion Laboratory in Pasadena, California, said in a statement. "The hazard is not an impact of the comet nucleus, but the trail of debris coming from it. Using constraints provided by Earth-based observations, the modeling results indicate that the hazard is not as great as first anticipated. Mars will be right at the edge of the debris cloud, so it might encounter some of the particles -- or it might not."

NASA's two orbiters currently buzzing the Martian sky, the Mars Reconnaissance Orbiter and Mars Odyssey, have already begun adjusting their trajectories to get out of the comet's path.

Meanwhile, the Mars Atmosphere and Volatile Evolution (MAVEN), which is on track to reach Mars orbit on Sept. 21, has been programmed to initiate a precautionary maneuver before it begins the main scientific phases of its mission in November.

NASA officials explain all three orbiters will end up on the opposite side of the planet at the time the comet is anticipated to pass by.

Days before and after the Comet C/2013 A1 Siding Spring flyby, NASA will use several instruments on the Mars orbiters to examine the comet nucleus, the coma surrounding the nucleus and the tail, along with any potential effects the deep space traveler may have on the Martian atmosphere.

NASA does not anticipate the comet will cause any hazard to the Opportunity and Curiosity rovers currently exploring the planet's surface.