Stardust Mission Finds ‘Fire and Ice’
The first results from NASA’s Stardust mission to collect material from a comet has turned up a major surprise -- minute fragments of minerals formed under high temperatures rather than the simpler dust scientists had expected.
The minerals were formed at temperatures present only in the nebulae surrounding primitive stars, indicating that they were either created during the formation of our sun and ejected to the farthest reaches of the solar system or were created at other stars, drifting across interstellar space to reach our neighborhood.
“Remarkably enough, we have found fire and ice,” principal investigator Donald Brownlee of the University of Washington said at a news conference Monday. “We are finding these high-temperature minerals in materials from the coldest place in the solar system.”
Researchers will eventually be able to pinpoint the origin of the minerals by examining their isotopic composition, he said.
The $200-million Stardust mission was launched in February 1999 and swung by comet Wild 2 five years later, coming within 147 miles of the hamburger-shaped comet. Stardust deployed a tennis-racket-shaped arm to collect dust from the comet’s tail.
The samples were trapped in aerogel, a material that has the same composition as glass but is 99.9% air. The sample container was ejected from the probe and parachuted to the Utah desert on Jan. 15.
Since then, the team has begun the tedious process of extracting the cometary grains from the aerogel, slicing them into ultra-thin fragments only a few hundred atoms wide, and distributing them to more than 150 researchers worldwide for analysis.
So far, the researchers have looked at six of the 132 individual cubes of aerogel, said deputy principal investigator Peter Tsou of the Jet Propulsion Laboratory in La Canada Flintridge, where the mission was conceived and managed.
The aerogels are “full of particles,” Tsou said. “Mission accomplished.”
More than two dozen of the dust particles can be seen with the naked eye, he said, and the tracks left by the others are clearly visible. Most have a large entry site -- indicating, perhaps, that volatile materials in the dust grains exploded on impact. The wide entry gives way to a much narrower track as the particles’ energy dissipated.
Most of the particles “are much, much smaller than a human hair,” said co-investigator Michael Zolensky of the Johnson Space Center in Houston, where the particles are being stored and processed.
The reverse side of the aerogel probe was opened as the craft made its long journey from Earth to Wild 2, but the team has not begun to examine those particles, which scientists believe are interstellar dust and are smaller still.
“There are so few of them and they are so tiny that we have little idea how to study them today,” Zolensky said.
Later this month, the team will photograph the aerogel containing the interstellar dust and put the images on the Internet in a project called Stardust at Home. People will be able to view the images and help scientists locate the particles.
