In a risky flyby, NASA's Deep Space 1 spacecraft successfully navigates past comet Borrelly, giving researchers the best look ever inside the glowing core of icy dust and gas.

The space probe's close encounter with comet Borrelly provides the best-resolution pictures of any comet to date. The already-successful Deep Space 1, without protection from the little-known comet environment, whizzes by just 2,200 kilometers (1,400 miles) from the rocky, icy nucleus of the 10-kilometer-long (more than 6-mile-long) comet.

Deep Space 1 completed its primary mission testing ion propulsion and 11 other advanced, high-risk technologies in September 1999. NASA extended the mission, taking advantage of the ion propulsion and other systems to undertake this chancy but exciting encounter with the comet.