On October 19, 2014, Comet Siding Spring had a remarkably close encounter with Mars, buzzing the Red Planet at just one-third the distance from Earth to the moon. The comet hails from far beyond Pluto's orbit, originating in a region of icy debris known as the Oort cloud. Comets from the Oort cloud are both ancient and rare. Such comets were born during the formation of our solar system and are older than Earth itself. As Comet Siding Spring passed by Mars, it left behind a trail of gas and dust. Using space and ground-based telescopes, along with NASA’s fleet of Mars orbiters and rovers, scientists will study the composition of the comet and the effects of its gas and dust on the Martian atmosphere. Watch the video to learn more.