NASA plans to watch when comet passes close to Mars

NASA says it plans to observe a comet that will buzz Mars this year,coming about 10 times closer than any identified comet has ever flown past Earth. Comet C/2013 A1 Siding Spring will make its closest approach to the Red Planet, a distance of about 86,000 miles, Oct. 19, the space agency said Tuesday. Spacecraft orbiting Mars might get a good look at the nucleus of the comet as it speeds past, but there is also a chance dust particles the comet nucleus sheds could threaten those spacecraft, NASA scientists said. The level of risk won't be known for months, but NASA is already evaluating possible precautionary measures as it prepares for studying the comet, the scientists said. "Our plans for using spacecraft at Mars to observe comet Siding Spring will be coordinated with plans for how the orbiters will duck and cover, if we need to do that," said Rich Zurek, Mars Exploration Program chief scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. The comet was discovered Jan. 3, 2013, by Australia's Siding Spring Observatory. Its nucleus will come about as close to Mars as one-third of the distance between Earth and the moon, NASA said.