Extraterrestrial amino acids in Orgueil and Ivuna: Tracing the parent body of CI type carbonaceous chondrites

Abstract

Amino acid analyses using HPLC of pristine interior pieces of the CI carbonaceous chondrites Orgueil and Ivuna have found that ␤-alanine, glycine, and ␥-amino-n-butyric acid (ABA) are the most abundant amino acids in these two meteorites, with concentrations ranging from Ϸ600 to 2,000 parts per billion (ppb). Other ␣-amino acids such as alanine, ␣-ABA, ␣-aminoisobutyric acid (AIB), and isovaline are present only in trace amounts (<200 ppb). Carbon isotopic measurements of ␤-alanine and glycine and the presence of racemic (D͞L Ϸ 1) alanine and ␤-ABA in Orgueil suggest that these amino acids are extraterrestrial in origin. In comparison to the CM carbonaceous chondrites Murchison and Murray, the amino acid composition of the CIs is strikingly distinct, suggesting that these meteorites came from a different type of parent body, possibly an extinct comet, than did the CM carbonaceous chondrites. Carbonaceous chondrites provide some of the most primitive solar system material available for study and are known to contain a wide variety of organic compounds (1). In particular, one group of carbonaceous chondrites, the CIs, which have been altered extensively by water on their parent body, have been found to contain high abundances of organic carbon. Orgueil, the most well known CI carbonaceous chondrite, fell in France on May 14, 1864 at a time when organic and analytical chemistry were in their infancy. Nevertheless, by using techniques available at the time, chemists soon showed that the meteorite contained organic material probably of extraterrestrial origin (2). Some scientists even speculated that the Orgueil organic material was produced by extraterrestrial organisms and thus provided evidence for panspermia, a process wherein life on Earth was seeded by a bacterial spore from another world that had hitchhiked on a meteorite that had fallen to Earth (3). Pasteur briefly examined the Orgueil meteorite and found no evidence for bacteria, a finding that he evidently considered so unimportant that it was never published except in his notebooks (4).The possibility that Orgueil contained evidence for extraterrestrial life resurfaced in the 1960s when Nagy and coworkers published a series of papers claiming that the meteorite contained biogenic hydrocarbons along with ''organized elements'' that supposedly resembled fossilized algae (5, 6). These claims generated an intense debate, and soon it was shown that the hydrocarbons were terrestrial contaminants and the organized elements were ragweed pollen (7,8).Because of these controversies, the CI meteorite Orgueil has seldom been studied by using the modern analytical techniques now available to investigate organic compounds in meteorites. The last amino acid analysis of Orgueil was reported in 1972 when GC analysis using a chiral derivatizing reagent showed that the meteorite contained D-and L-amino acids and other amino acids such as ␤-alanine, ␣-aminoisobutyric acid (AIB), and ␤-AIB, which generally are not present in terrestrial living organisms (9). Surprisingly, Ivu...

The composition of ices in comet C/1995 O1 (Hale-Bopp) from radio spectroscopy

“…The glycine concentration is ≈7 × 10 −7 in mass in the CI-type meteorites Orgueil and Ivuna (Ehrenfreund et al 2001b), ≈2.5 × 10 −6 in the CM-type meteorites Murchison and Murray (Cronin & Chang 1993). In this respect, our limit in comet Hale-Bopp is hardly significant.…”

Methylammonium methylcarbamate thermal formation in interstellar ice analogs: a glycine salt precursor in protostellar environments

“…Numerous tentative detections of interstellar glycine have been reported but its identification has not yet been confirmed (Kuan et al 2003;Snyder et al 2005). Meteoritic glycine has been identified in both CM-and CI-type carbonaceous chondrites such as Murchison, Murray, Orgeuil, and Ivuna by using highly sensitive analytical techniques (Kvenvolden et al 1970;Cronin & Pizzarello 1997;Lawless 1972;Ehrenfreund et al 2001a;Botta & Bada 2002). In cometary coma, approximately 25 molecules have been detected by radio astronomy (Crovisier et al 1998;Bockelée-Morvan et al 2000;Despois 1999;Irvine et al 2000), but not glycine (Ehrenfreund et al 2002;Crovisier et al 2004).…”

Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M)

“…2−7, are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/559/A47 fallen to Earth. The isotopic composition and racemic distribution of these amino acids, in particular, suggest that they, or at least their direct precursors, have an extraterrestrial origin (see, e.g., Ehrenfreund et al 2001;Bernstein et al 2002;Elsila et al 2007, and references therein). More recently, the detection of glycine (NH 2 CH 2 COOH), the simplest amino acid, has even been claimed in samples from comet 81P/Wild 2 returned to Earth by NASA's Stardust spacecraft (Elsila et al 2009).…”