This fall, on Oct. 19, a comet will blast past Mars at a distance of only 86,000 miles (138,000 kilometers) - a little more than one-third the average distance between Earth and the moon. NASA is anticipating the event as a great viewing opportunity for its Red Planet robot residents (as is ESA) but until then all the action will be captured by Earthbound telescopes, including the orbiting Hubble Space Telescope, which acquired the image above on March 11.
ANALYSIS: Hubble Witnesses Mysterious Breakup of Asteroid
Showing the 12,000-mile (over 19,000 km) wide coma of comet C/2013 A1 - aka Comet Siding Spring, after the observatory in Australia where astronomer Robert McNaught first spotted it last year - the Hubble image has been processed to better discern what appear to be two separate jets coming out of opposite ends of its nucleus.
Measurements of these jets will help astronomers determine the rotation of Siding Spring's nucleus, an important factor for comets as that can affect their appearance, orbits, and even whether or not they hold together at perihelion - the closest approach to the sun.