Comet Siding Spring from Mars. Illustration of Comet Siding Spring seen from the Martian surface during its encounter with Mars. Comet Siding Spring (C/2013 A1) passed within around 132,000 kilometres of Mars on 19 October 2014. This was extremely close in planetary terms, and the planet was showered with cometary dust and particles, detected by the orbiting spacecraft. Victoria, a Martian crater previously visited by NASA's Opportunity rover, is visible in the foreground. Both NASA's Mars rovers (Curiosity and Opportunity) obtained images of the comet passing by Mars.