This image shows the most recent observations of the 2-mile-wide (4-kilometer-wide) comet 67P/Churyumov-Gerasimenko, which is the upcoming target of the European Space Agency's Rosetta mission. Rosetta is expected to rendezvous with the comet in August 2014.
The image was taken on October 5, 2013, by the Very Large Telescope of the European Southern Observatory in Chile. The comet was around 300 million miles (500 million kilometers) from Earth at the time. (It then passed behind the sun and out of view from Earth's perspective).
Image credit: ESO/Max Planck Institute for Solar System Research
Note: For more information, see PIA17664: U.S. Instruments Aboard Rosetta, PIA17665: Electronics for a Spectrometer, PIA17666: Rosetta at Comet, NASA Instruments on European Comet Spacecraft Begin Countdown, Rosetta: To Chase a Comet, and Rosetta Wide Awake as Check-Up Continues.