Hartley  2, a small periodic comet with an orbital period of 6.46 years, will pass just 11 million miles from Earth on Oct. 20, 2010. http://en.wikipedia.org/wiki/ 103P/Hartley Green comet 103P/Hartley 2 is approaching Earth for a close encounter on Oct. 20th. At that time, the comet will be only 11 million miles from Earth