The National Academies Press

Currently Skimming:

3 Meteorites
Pages 37-51

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.

From page 37... ... It was the presence of organic matter identified in the carbonaceous chondrites that captured the interest of chemists in the 1800s.1,2 Notwithstanding this interest, analytical techniques capable of describing the organic constituents of these meteorites were not available until the 1950s, when a rising interest in space science coupled with advances in analytical chemistry led to a rejuvenation of efforts to characterize the organic matter in carbonaceous chondrites. Read the entire page →
From page 38... ... Thus, even though many of the soluble compounds in Murchison are recognizable as biochemically significant, e.g., the amino acids, their stereochemical and isotopic characteristics clearly identify them as both extraterrestrial and nonbiological.9 The classes of soluble meteoritic organic compounds that have familiar biochemical counterparts include the amino acids, fatty acids, purines, pyrimidines, and sugars.10,11 Additional soluble constituents include alcohols, aldehydes, amides, amines, mono- and dicarboxylic acids, aliphatic and aromatic hydrocarbons, heterocyclic aromatics, hydroxy acids, ketones, phosphonic and sulfonic acids, sulfides and ethers.12-14 Concentrations of the major representatives of these classes vary widely from less than 10 parts per million (amines) to tens of parts per million (amino acids) Read the entire page →
From page 39... ... Only eight out of 20 of these terrestrial, biological amino acids have been identified in meteorite extracts. Mechanism of Formation of Organic Compounds in Carbonaceous Chondrites The observed patterns of variation in molecular structure and abundance in carbonaceous chondrites suggest initial synthesis routes involving the formation and random recombination of small, free radicals.21,22 Such reactions tend to produce the greatest variation in possible structural isomers at lower carbon numbers. Read the entire page →
From page 40... ... . However, in contrast to carbonaceous chondrites such as Murchison, Orgueil, and Ivuna,23,24 virtually no amino acids are detected in extractions obtained from the Tagish Lake meteorite when it was treated with water or organic solvents. Read the entire page →
From page 41... ... Isotopic analyses of these N-heterocycles reveal enrichment in D, 13C, and 15N at levels outside the terrestrial range.40 Similar enrichments in heavy isotopes are signatures of low-temperature reactions in interstellar clouds and support an extraterrestrial source for these molecules. Macromolecular Organic Matter in Carbonaceous Chondritic Meteorites The majority of organic matter contained within carbonaceous chondrites is in the form of nonextractable, presumably macromolecular carbon. Read the entire page →
From page 42... ... Within these inorganic carbon phases, many individual constituents (e.g., nanodiamond grains and SiC grains) carry large isotopic anomalies that point to specific stellar origins such as supernovas for the nanodiamonds or carbon stars and novas for SiC, fullerene, and graphite.52-54 Isotopic Characteristics of Insoluble Organic Matter The bulk isotopic compositions of IOM fractions of numerous carbonaceous chondrites are well established. Read the entire page →
From page 43... ... Bailey and colleagues suggested that the observed enantiomeric excesses could have been induced by circularly polarized light scattered from dust in regions of high-mass-star formation.69 These sources occur more widely than do the supernova remnants or pulsars that were first proposed by Rubenstein et al. as sources of circularly polarized synchrotron radiation.70 However, both theories do not take into account that amino acids are very fragile compounds, which are easily destroyed by particle radiation and even by low-energy ultraviolet photons.71 ORGANIC CARBON IN UNEQUILIBRATED ORDINARY CHONDRITES AND ENSTATITE CHONDRITES Most analyses of organic material pertain to Murchison and a few other carbonaceous chondrites. Read the entire page →
From page 44... ... On pyrolysis, the major components of this complex organic matter found in both meteorites are aromatic and alkylaromatic hydrocarbons, phenol, and benzonitrile. Analysis of individual molecules in the Nakhla pyrolysate showed that they were similar to materials found in carbonaceous chondrites. Read the entire page →
From page 45... ... How should plans be developed and proposals solicited for the curation and coordinated, intensive investigation of the composition of organic materials in carbonaceous chondrites, unequilibrated ordinary chondrites, and SNC meteorites? While the available samples are not improving on the shelf, significant developments in analytical technology have occurred in the past few decades, and so the time is ripe for investment of significant portions of the available stocks in a new round of analyses. Read the entire page →
From page 46... ... -- charged to coordinate plans and develop priorities for the intensive investigation of the composition of organic materials in carbonaceous chondrites, SNC meteorites, and ordinary chondrites containing volatiles (including rare gases) that suggest relationships to the carbonaceous chondrites. Read the entire page →
From page 47... ... In addition to ANSMET's long-standing NSF sponsorship, NASA has funded an expanded field effort, and this paid off with the U.S. team's recovery in December 2003 of the first martian meteorite in 9 years, as well as the collection of large numbers of carbonaceous chondrites. Read the entire page →
From page 48... ... The task group suggests that the greatest near-term scientific impact from a given expenditure of funds will result not from the enhancement of meteorite collecting programs but rather from the acquisition of a significant piece of the Tagish Lake meteorite so that it can be made available for study by the broader scientific community. Recommendation: The scientific significance of the Tagish Lake meteorite is such that NASA, the National Science Foundation, the Smithsonian Institution, and other relevant organizations and agencies in the United States and their counterparts in Canada should examine the means by which a significant portion of this fall can be acquired, by purchase, exchange, or some other mechanism, so that samples can be made more widely available for study by the scientific community. Read the entire page →
From page 49... ... Cooper, and J.B. Bada, "Extraterrestrial Amino Acids in Orgueil and Ivuna: Tracing the Parent Body of CI-type Carbonaceous Chondrites," Proceedings of the National Academy of Sciences 98: 2138-2141, 2001. Read the entire page →
From page 50... ... Pizzarello, and J.S. Frye, "13C NMR Spectroscopy of the Insoluble Carbon of Carbonaceous Chondrites," Geochimica et Cosmochimica Acta 51: 299-303, 1987. Read the entire page →
From page 51... ... Maechling, R.N. Zare, and C.M.O'D Alexander, "Analysis of Polycyclic Aromatic Hydrocarbons in Seventeen Ordinary and Carbonaceous Chondrites," Lunar and Planetary Science 23: 233-234, 1992. Read the entire page →

From page 37...

... It was the presence of organic matter identified in the carbonaceous chondrites that captured the interest of chemists in the 1800s.1,2 Notwithstanding this interest, analytical techniques capable of describing the organic constituents of these meteorites were not available until the 1950s, when a rising interest in space science coupled with advances in analytical chemistry led to a rejuvenation of efforts to characterize the organic matter in carbonaceous chondrites.

3 Meteorites Pages 37-51

3 Meteorites
Pages 37-51