Medicine & TechnologyIt’s been a flyby anticipated for months, and one whose arrival sparked much commotion at NASA’s headquarters this past weekend. Hurtling through the night sky at nearly 125,000 miles per hour, Comet C/2013 A1 Siding Spring passed right by the planet Mars early Sunday afternoon, Oct. 19, coming in close contact with the Martian outer atmosphere at about 2:27pm ET.