By Mike Wall, Senior Writer A comet's close shave with Mars this weekend could reveal some key insights about the Red Planet and the solar system's early days, researchers say. Comet Siding Spring will zoom within 87,000 miles (139,500 kilometers) of Mars at 2:27 p.m. EDT (1827 GMT) on Sunday (Oct. 19). Scientists will observe the flyby using the fleet of spacecraft at Mars, studying the comet and any effects its particles have on the planet's thin atmosphere. "On Oct. 19, we're going to observe an event that happens maybe once every million years," Jim Green, director of NASA's planetary science division, said in a news conference earlier this month. "This is an absolutely spectacular event." More via Space.com.