Scientists worldwide are pleased with the images and data generated by a constellation of at least 15 spacecraft-five of them in Mars orbit-when they turned away from their normal targets Oct. 19 to study an extremely rare visitor from the outer edge of the Solar System. The Comet designated C/2013 A1 Siding Spring passed within 87,000 mi. of Mars, giving spacecraft and ground telescopes an unprecedented chance to study a pristine object from the Oort Cloud close up. The vast array of objects older than the Earth normally orbit the Sun as far as a quarter of the distance to the nearest star, at the outer limit of the Sun's gravitational influence.
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