NASA released Thursday an image of a comet that, on Oct. 19, will pass within 84,000 miles of Mars -- less than half the distance between Earth and our moon.
The image on the left, captured Mar. 11 by NASA's Hubble Space Telescope, shows comet C/2013 A1, also called Siding Spring, at a distance of 353 million miles from Earth. Hubble can't see Siding Spring's icy nucleus because of its diminutive size. The nucleus is surrounded by a glowing dust cloud, or COMA, that measures roughly 12,000 miles across.