Halley's Comet photographed in 1985. Viewers on Earth were disappointed because poor visibility hindered viewing with the naked eye. But spacecraft from Russia, Japan, and the European Space Agency were able to make the trip out into space and get a much better appreciation of this dazzling - and constant - visitor to our planet.
Credit: Getty Images
NASA's Deep Space 1 probe took this photograph of Comet Borrelly in September 2001.
NASA's Deep Impact spacecraft snapped this amazing picture of another periodic visitor, Comet Tempel 1, photographed on July 4, 2005, shortly after a probe crashed into the comet