On October 19, 2014, Comet Siding Spring streaked by Mars. At its closest, this icy traveler from the outer-outer solar system was a piddly 140,000 kilometers away from the red planet.
That’s about one-third the Earth-Moon distance.
Fortunately, NASA’s biggest eye-in-the-sky swiveled to capture the close encounter. Above, we see the resulting Hubble Space Telescope image of Siding Spring and Mars. The planet and comet were shot independently, and the star-studded backdrop added in later, based on data from the Palomar Digital Sky Survey. That’s because Mars is so much brighter than the comet — about 10,000 times brighter — that it would have been tricky to see both objects in a single exposure.
Hubble’s image joins those captured by the fleet of robots Earth has stationed on and around our ruddy neighbor.