Considering how often comets make headlines, it's surprising how little is known about their icy cores. Scientists hope the Contour spacecraft, launching this month, will change that.
A joint project of NASA, Cornell, and the Johns Hopkins Applied Physics Laboratory, the spacecraft will fly by at least two comets on its four-year intrastellar journey-Comet Encke, in November 2003, and Comet Schwassmann-Wachmann 3, in June 2006.
THE COMEBACK COMETS
When our most famous space visitors will be back.
Last Seen: 1986
Where It Is: 2.57 billion miles away, between Uranus and Neptune
Next Visit: 2061
Last Seen: 1997
Where It Is: 1.46 billion miles away, between Saturn and Uranus
Next Visit: 3557
Last Seen: 1996
Where It Is: 1.67 billion miles away, between Saturn and Uranus
Next Visit: 31446