Wednesday, December 20, 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 December 15 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. [Astrobiology]
Continued at "NASA Study Finds New Kind of Organics in Stardust Mission"
*A Science Special Online Collection: Stardust includes:
1) Organics Captured from Comet 81P/Wild 2 by the Stardust Spacecraft
Organics found in comet 81P/Wild 2 samples show a heterogeneous and unequilibrated distribution in abundance and composition. Some organics are similar, but not identical, to those in interplanetary dust particles and carbonaceous meteorites. A class of aromatic-poor organic material is also present. The organics are rich in oxygen and nitrogen compared with meteoritic organics. Aromatic compounds are present, but the samples tend to be relatively poorer in aromatics than are meteorites and interplanetary dust particles. The presence of deuterium and nitrogen-15 excesses suggest that some organics have an interstellar/protostellar heritage. Although the variable extent of modification of these materials by impact capture is not yet fully constrained, a diverse suite of organic compounds is present and identifiable within the returned samples.
2) Isotopic Compositions of Cometary Matter Returned by Stardust
Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild 2 particle fragments; however, extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Nonterrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single 17O-enriched circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is 16O-enriched, like refractory inclusions in meteorites, suggesting that Wild 2 contains material formed at high temperature in the inner solar system and transported to the Kuiper belt before comet accretion.
3) There is a video (or rather, 5 videos) presentation here
Also see "Astrobiology and Stardust"
Carl Sagan once said "We are all star stuff." But how? What does that really mean? One of the fundamental questions of astrobiology, how does life originate and evolve?, provides a structure in which to examine the relationship between life and the cosmos. Everywhere life has been found on Earth, which is essentially every place in which it has been sought, life's intimate connection with water has also been found. Within the framework of contemplating life's cosmic origins, one must also ask about the history of water on Earth. NASA's Stardust mission has provided the opportunity for astrobiologists to gain deeper insight into this history.
Many scientists from the NASA Astrobiology Institute** (NAI) have been involved in the Stardust mission, spearheaded by none other than Stardust PI Don Brownlee at the University of Washington. The list also includes Scott Sanford of the NAI NASA Ames Team, lead author of one of the papers in this week's Science, and George Cody of the NAI Carnegie Institution of Washington Team.
"Comets are important to the understanding of the origin of life," said Brownlee, "we have always considered Stardust an astrobiology mission." Results from analysis of the Stardust samples have brought new insight to bear on the relationship between the inner and outer solar system. "The samples we've obtained from Stardust have helped us understand both the origin of water and other volatiles, as well as their delivery mechanisms to the early Earth," said Brownlee.
-------**From "About the NAI":
"Astrobiology is devoted to the scientific study of life in the universe - its origin, evolution, distribution, and future. This multidisciplinary field brings together the physical and biological sciences to address some of the most fundamental questions of the natural world: How do living systems emerge? How do habitable worlds form and how do they evolve? Does life exist on worlds other than Earth? How could terrestrial life potentially survive and adapt beyond our home planet?
Scientists now realize that the origin and evolution of life itself cannot be fully understood unless viewed from a larger perspective than just our own Earth. Biologists are working with astronomers to describe the formation of life's chemical precursors, to discover new planets, and to determine their habitability; with chemists to understand the transition from molecular interaction to life itself; with geologists to search for evidence of water and key minerals on other planets; with paleontologists and evolutionary molecular biologists to look for and comprehend the earliest forms of life, as well as with climatologists, planetary scientists, and researchers from nearly every field of science.
In 1998 NASA established the NASA Astrobiology Institute (NAI) as one element of its research program in astrobiology. The NAI is currently composed of 12 Lead Teams, which together represent over 700 investigators across the United States, and it has international partnerships with astrobiology research organizations around the world.
The major research themes of astrobiology are described in detail in the NASA Astrobiology Roadmap."