Fed II Star - January 29, 2006

REAL LIFE NEWS: STARDUST HELPS WITH METEOR RESEARCH

NASA's Stardust capsule fell to Earth on January 15, bringing back samples of comet dust which have scientists falling over themselves to examine. But before the capsule was retrieved from its landing place in the Utah desert, it was already contributing to research, but not on comets: on meteors!

The descent of Stardust, as it raced across the skies of northern Nevada in a blazing neon-pink fireball, was "like a really great meteor," says Wayne Edwards at the University of Western Ontario in Canada. "But we knew all the properties of the object prior to its actual arrival." This precise knowledge, including its mass and velocity, allowed Edwards and his colleagues to record Stardust's arrival and use it as a baseline for analysing "real" meteors in the future.

One of the things the scientists did was to bury seismometers about half a metre below ground in hopes of detecting a tiny local earth tremor caused by the sonic boom or "airwave" of the capsule's re-entry. They also recorded the passage of the airwave through the air in infrasound - the inaudible, low-frequency part of the sonic boom. Infrasound travels much faster than audible sound. Data from Starburst's airwave will help scientists figure out the energy and size of incoming meteors from great distances, even when they are not observed visually.

Another group filmed the capsule's descent from several kilometres away as it passed overhead. The capsule was visible from their position for about half a minute, and during this time it slowed perceptibly from its initial speed of 12 km per second to 3 km per second. It also changed color from near-white to a deep, rosy red.

Alan Hildebrand, who works on recovering fragments from meteors that explode on re-entry, will use these results to see how well the standard methods of determining a meteor's trajectory stack up against the known trajectory of Stardust.

A planeload of NASA scientists made aerial observation of Stardust as it fell to Earth, from a DC-8 plane. George Raiche says, "What I saw aws a bright light with a glowing head and persistent trail." During the flight, he manned a spectroscope that broke down the light of this incandescent glow into its constituent wavelengths. This will help to reveal the profile of temperatures experienced by the capsule's heat shield - of particular interest because Stardust's high-velocity re-entry means it endured about 10 times the heating rate that the space shuttle typically experiences. The speeds and temperatures are similar to what could one day face capsules bringing astronauts back from NASA's proposed missions to the moon.

All this, before the capsule was even collected!