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Three Mars probes hide behind planet, avoid comet debris

"This comet is making its first visit this close to the sun from the outer solar system's Oort Cloud," NASA said.

By Brooks Hays
An artistic representation of NASA's probes sheltering in anticipation of the comet's debris. (NASA/JPL-Caltech)
An artistic representation of NASA's probes sheltering in anticipation of the comet's debris. (NASA/JPL-Caltech)

WASHINGTON, Oct. 20 (UPI) -- NASA's Mars orbiters and rovers are apparently unscathed after a comet passed worryingly close to small, reddish planet over the weekend.

Comet C/2013 A1, dubbed Siding Spring, was never going to hit the any of the spacecrafts directly, but NASA engineers positioned the probes in the shadow of the Red Planet so to be protected from the barrage of space debris that trails behind comets. NASA's rovers were essentially on their own.

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Siding Spring buzzed by at a cool 125,000 miles per hour, coming within 88,000 miles of the Martian surface -- three times closer than the moon is to Earth and the closest comet flyby astronomers have ever witnessed.

Siding Spring is an Oort cloud comet, which means it traveled from a remote spherical region of the solar system far beyond the last of the defined planets. Scientists say the comet is likely remarkably similar in its composition to its earliest form, forged some 4.5 billion years ago.

"Siding Spring probably got knocked into the inner Solar System by the passage of a star near the Oort Cloud," Carey Lisse, a researcher at the Johns Hopkins' Applied Physics Laboratory, told the BBC. "So think about a comet that started to travel probably at the dawn of man and it's just now coming in."

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"And the reason we can actually observe it is because we've built satellites and rovers and we've now got these outposts at Mars," Lisse added. "That's pretty exciting."

NASA officials say that both rovers, Curiosity and Opportunity, on the Mars surface were attempting to take photographs of the passing comet, but experts say their success in doing so is unlikely. They were likely able to capture imagery of meteorites burning through the thin Martian atmosphere. Comet-related data and imagery collected by the rovers and probes is expected to be released by NASA in the coming days.

"This comet is making its first visit this close to the sun from the outer solar system's Oort Cloud, so the concerted campaign of observations may yield fresh clues to our solar system's earliest days more than 4 billion years ago," NASA said in a statement.

The window comets might offer scientists into the solar system's past is one of the reasons space agencies like NASA and the European Space Agency (ESA) are working on a mission to track down and lasso a comet. The ESA probe Rosetta, which is currently orbiting Comet Churyumov-Gerasimenko, is expected to launch a rover-type vehicle that will land on the comet's surface in November.

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