All eyes on comet's belly
2005-07-06 10:47
Alicia Chang
Los Angeles - The collision of a Nasa space probe and a potato-shaped comet hurled a bright cloud of debris into space at the speed of a jetliner, scientists said.
The Hubble Space Telescope took a series of pictures of the July 4 impact that initially showed comet Tempel 1 as a fuzzy dot that grew four times brighter 15 minutes after the collision. The fan-shaped cloud of gas and dust flew outward at about 800 kph.
"This is pretty dramatic," said Paul Feldman, a professor of astronomy and physics at Johns Hopkins University, who observed the impact with the Hubble telescope.
The Hubble findings were among observations pouring in from telescopes in space and on the ground. For example, an infrared camera on the Very Large Telescope in Chile detected a colour change in the plume, suggesting different-size dust particles were sprayed from the comet and were travelling at different speeds through space.
During the weekend, an 369kg copper "impactor" separated from Nasa's Deep Impact spacecraft, and guided itself into Tempel 1 in a crash that gave off energy equal to detonating nearly five tons of TNT.
The impact caused a bright flash of light, then a larger one as a plume of debris spilled from the comet's belly thousands of kilometres into space. This suggests the probe struck a surface that was soft and powdery before penetrating trapped gas and ice beneath, said Pete Schultz, a Deep Impact co-investigator.
Cosmic dust
But other researchers said initial ultraviolet readings taken by Nasa's Swift satellite detected a dramatic rise in UV light - indicating the surface was hard or there was solid material underneath.
The larger-than-expected debris cloud has prevented scientists from peering into the impact crater. Scientists said it could take at least a week for the cosmic dust to settle before they get their first glimpse at the inside of a comet.
Comets contain the frozen primordial ingredients of the young solar system. Studying the debris hurled from the interior of Tempel 1 and the crater left behind could yield clues to how the sun and planets formed 4.5 billion years ago.
Initial estimates were that the collision would blast a hole ranging from the size of a house to a stadium. Scientists cannot yet measure the crater's size, but said it was probably larger than a house.
The impactor beamed back real-time photos as it steered itself toward the comet. The last image was taken 29 kilometres from the comet nucleus three seconds before impact, giving scientists the most close-up pictures of a comet. The mother ship also observed the collision and stunned scientists with dramatic photos of the crash and aftermath.
Deep Impact blasted off on January 12 from Cape Canaveral, Florida, on a 431-million-kilometre voyage to Tempel 1, a comet half the size of Manhattan located 133.5 million kilometres from Earth.
On the net:
www.nasa.gov/deepimpact
- AP