After lurking in the outer reaches of the solar system for the past one million years, a comet is heading for a close encounter with Mars. The Hubble Space Telescope is keeping tabs on the icy interloper, seen in just-released images.
Comet C/2013 A1 (Siding Spring), which now lies some 353 million miles (568 million kilometers) from Earth, was discovered by Australia’s Robert McNaught, a prolific comet and asteroid hunter, more than a year ago. NASA’s Near-Earth Object Program Office at the Jet Propulsion Laboratory, in Pasadena, California, has been refining the comet’s exact trajectory ever since.
While researchers have ruled out a direct collision with Mars, the dusty coma of the comet (which is nearly as large as the entire Earth) will sweep directly across the red planet. The comet core, or nucleus, is expected make its closest approach to the red planet on October 19 at 2:28 p.m. ET. It will pass within 85,600 miles (137,760 kilometers) of Mars—less than half the distance from the Earth to the moon.