December 14, 2006
A team of scientists found a new class of organics in comet dust captured from Comet Wild 2 in 2004 by NASA's Stardust spacecraft.
The discovery is described in a technical paper, "Organics Captured from Comet Wild 2 by the Stardust Spacecraft," in the Dec. 15, 2006, issue of Science Express, the online edition of the journal Science.
In January 2004, the Stardust spacecraft flew through comet dust and captured specks of it in a very light, low-density substance called aerogel. Stardust's return capsule parachuted to the Utah Test and Training Range on Jan. 15, 2006, after a seven-year mission. The science canister containing the comet particles and interstellar dust particles arrived at Johnson Space Center on Jan. 17. From there, the cometary samples have been processed and distributed to about 150 scientists worldwide who are using a variety of techniques to determine the properties of the cometary grains.
"A portion of the organic material in the samples is unlike anything seen before in extraterrestrial materials," said Scott Sandford, the study's lead author and a scientist from NASA's Ames Research Center in California's Silicon Valley. "Capturing the particles in aerogel was a little bit like collecting BBs by shooting them into Styrofoam."
The comet organics collected by the Stardust spacecraft are more “primitive” than those seen in meteorites and may have formed by processes in nebulae, either in space clouds between the stars, or in the disk-shaped cloud of gas and dust from which our solar system formed, the study's authors found.
"Comets are a major source of the water and carbon on the moon," said S. Pete Worden, NASA Ames director. "Therefore, understanding comets will help scientists learn what natural resources to search for on our nearest neighbor in space -- resources that will aid astronauts in exploration beyond Earth," Worden explained.
The study's scientists used many highly sophisticated, state-of-the-art techniques to analyze the Stardust samples.
Several of the analyses indicated that the samples contain polycyclic aromatic hydrocarbons (PAHs), scientists said. PAHs are molecules made of carbon and hydrogen that are common in interstellar space – and in barbeque grill soot.
Certain PAHs chemical varieties also contain oxygen and nitrogen. Some scientists believe that these PAHs variants exist in interstellar space as well. They are of interest to astrobiologists because these kinds of compounds play important roles in terrestrial biochemistry, according to Sandford.
"Our studies of the comet dust show that the organics are very rich in oxygen and nitrogen," Sandford said. "The data are not incompatible with some of it being in the PAHs, but we still have a lot to learn in this area."
Although some of the other organics captured by the Stardust spacecraft look somewhat similar to the fairly stable organics found in meteorites, Sandford noted that many of the organic compounds appear to be very volatile. One sample even showed an abundance of material containing alcohols.
Many scientists believe that comets are largely made of the original material from which our solar system formed and could contain pre-solar system, interstellar grains. According to scientists, continued analysis of these celestial specks may well yield important insights into the evolution of the sun, its planets and possibly, even the origin of life.
"I anticipate that people will be asking for and working on these samples for decades to come," said Sandford. "What we report in the papers that appear this week is just the beginning of what we will learn from these samples. One of the advantages of returned samples is that they are available for study into the future, a gift that keeps on giving."
The organics paper is one of seven in the journal Science reporting the findings of the preliminary examination team that made the initial study of the cometary samples.
The Jet Propulsion Laboratory, Pasadena, Calif., manages the Stardust mission for NASA's Science Mission Directorate, Washington. Dr. Peter Tsou of JPL is the deputy principal investigator and is a co-author of the paper.
For more information about Stardust studies and other mission information, visit:
Media contact: DC Agle/JPL