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Comet smash hits the spot


Kaboom! The smash into comet Tempel 1 as it happened (Image: NASA/JPL-Caltech/UMD)

The mission to smash into a comet went off with a bang yesterday, 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," says Dr Don Yeomans, a scientist at NASA's Jet Propulsion Laboratory in Pasadena.

The spectacular collision, 134 million kilometres away 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 came in contact with a comet's nucleus.

"As of now, I think we have a completely different understanding of our solar system," says laboratory director Dr Charles Elachi. "Its success exceeded our expectations."

The washing machine-sized probe, which performed three final targeting manoeuvres 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 vapourised immediately following the collision, which occurred at 37,100 kilometres per hour just before 16:00 AEST (06:00 UTC).

The probe was released by the mission's mother ship Deep Impact about 24 hours before the collision.

"The impact was bigger than I expected, and bigger than most of us expected," Yeomans says. "We've got all the data we could possibly ask for and the science team is ecstatic."

It could take months to analyse all the data from the crash, says Professor Mike A'Hearn, the mission's lead scientist.

Three hours after the impact, just 10% of the data had been transmitted back to Earth.

Comets are made of gas, dust and ice from the solar system's furthest 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.

Experts had disagreed on how dense the comet's nucleus would be, but the size of yesterday's blast appeared to rule out a more porous composition that would have brought the probe to a slower halt, A'Hearn says.

Images taken by the impactor, showing a comet's nucleus in far greater detail than ever before, revealed several circular craters on the surface of Tempel 1.

The size of the crater formed by the copper-fortified impactor was not yet known, but had been expected to range from that of a large house to a football stadium.

The mother ship, which recorded the impact of the blast from as close as 500 kilometres away, survived the mission unscathed, scientists say.

Tags: science-and-technology, astronomy-space