Bull's Eye

A NASA spacecraft collided with a comet a third the size of Hong Kong, creating a brilliant cosmic smashup that capped a risky voyage to uncover the building blocks of life on Earth. ``We hit it just exactly where we wanted to,'' said Don Yeomans, a scientist at NASA's Jet Propulsion Laboratory in Pasadena, California. The spectacular collision,134 million kilometers from Earth, unleashed a spray of below-surface material formed billions of years ago during the creation of the solar system. It was the first time a craft was in contact with a comet's nucleus. ``As of now, I think we have a completely different understanding of our solar system,'' said laboratory director Charles Elachi. ``Its success exceeded our expectations.'' The washing machine-sized probe, which performed three final targeting maneuvers in the mission's last two hours, crashed into comet Tempel 1's brightest spot right on schedule, snapping images of its rocky terrain up until 3.7 seconds before impact. The craft was vaporized immediately following the collision, which occurred at 37,100 km/h. An image of the crash Monday 12.52am Hong Kong time taken by Deep Impact, the mother ship, showed a brilliant burst of material from the bottom of the avocado-shaped comet. The probe was released by Deep Impact 24 hours before the collision. ``The impact was bigger than I expected, and bigger than most of us expected,'' Yeomans said. ``We've got all the data we could possibly ask for and the science team is ecstatic.'' Scientists and engineers in the US$333 million (HK$2.6 billion) mission's control room cheered and hugged one another upon confirmation of the crash. It could take months to analyze all the data from the crash, according to Mike A'Hearn, the lead scientist. Three hours after the impact, just 10 percent of the data had been transmitted back to Earth. ``We are just basically starting our work now,'' A'Hearn said. ``I look forward to a wealth of data, which will take me to retirement.'' Comets are made of gas, dust and ice from the solar system's farthest regions. They often show bursts of activity, during which their surfaces crack to create tails of dust. Scientists think comets may have been responsible for first bringing water to Earth by crashing into its surface. Images captured by the impactor, showing the nucleus in greater detail than ever before, revealed several circular craters on Tempel 1. The size of the crater formed by the impactor is expected to range from that of a large house to a football stadium.