Deep Impact makes an impression on Tempel-1

(Big) bang on target

At around ten-to-seven this morning (BST) the NASA space probe Deep Impact lived up to its name and smashed into the Comet Tempel-1. The impact sent up a cloud of dust and gas far bigger than anyone had expected, making the comet, briefly, almost 11-times brighter than it was previously.

NASA TV image of the impact as seen from the fly-by vehicle

Deep Impact is a two-spacecraft mission designed to smash a 360kg probe into the nucleus of a comet, giving scientists their first ever glimpse of what lies below the surface layer of the nucleus.

Footage of the approach of the impactor showed the on-board cameras being buffeted by dust and debris from the comet, and the optics being gradually sandblasted down. A NASA spokesman commented: "Our brave little spacecraft is in a very hostile environment".

As the craft got closer to the nucleus, although the image remained quite grey and fuzzy, it was possible to make out craters on the surface of the 14km by 4km rock. NASA was aiming to hit the comet within one kilometre of its centre of mass, and when the impactor hit on target, the scientists at NASA mission control were jumping up and down, cheering, as you might expect.

Meanwhile back at the London press conference, reactions were a little more muted. It was only just 7:00am, after all. But once the images from the Faulkes telescope in Hawaii started coming in, everyone perked up a treat.

Steve Miller at the UK Infra Red Telescope, also based in Hawaii, told the assembled press (via the miracle of long distance telephony): "This is an enormous artificial outburst. The flare is still brightening as I'm watching it. It is well over ten times brighter than before the impact. Immediately after the probe hit, it doubled in brightness, and it has been steadily increasing ever since then."

The brightness reached a plateau at around 11 times its original intensity, before dropping off to about half that value. The researchers speculate that this increased brightness could be maintained for a number of days.

Professor John Zarnecki, one of the lead scientists in the Huygens mission, speculated that the increased brightness could be a combination of more material being dislodged, and the size of the particles being smaller. "More surface means more light," he explained.

Comet Tempel-1 getting brighter after impact. Images: Faulkes

Dr. Andrew Coates from the University of London's Mullard Space Science laboratory said that the images were hugely beyond expectations.

"We've had clues from other flybys, but now we can peer under the surface for the first time," he told The Register. "What we're seeing is unprocessed material left over from the early solar system."

He explained that the spectroscopic analysis of the cloud of dust would give scientists an idea of the ratio of various materials within the comet. "We'll really be able to constrain our models with the new data," he added.

Professor Monica Grady from the Open University said that she was particularly excited to see the ratio of organics to water in the dust. "How much organic material was around at the beginning of the solar system? This will help us understand the role comets played in seeding the building blocks of life, and Tempel-1 will show us what those blocks actually are."

She said she expected to see chains of carbon, polycyclics, ethanol and possibly even amino acids in the dust cloud. "But," she told us, "I would be absolutely aghast if we found DNA. That would really be overwhelmingly surprising." ®

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