7 September 2010 Chiral biomarkers and microfossils in carbonaceous meteorites
Author Affiliations +
Abstract
Homochirality of the biomolecules (D-sugars of DNA and RNA and L-amino acids of proteins) is a fundamental property of all life on Earth. Abiotic mechanisms yield racemic mixtures (D/L=1) of chiral molecules and after the death of an organism, the enantiopure chiral biomolecules slowly racemize. Several independent investigators have now established that the amino acids present in CI1 and CM2 carbonaceous meteorites have a moderate to strong excess of the L-enantiomer. Stable isotope data have established that these amino acids are both indigenous and extraterrestrial. Carbonaceous meteorites also contain many other strong chemical biomarkers including purines and pyrimidines (nitrogen heterocycles of nucleic acids); pristine and phytane (components of the chlorophyll pigment) and morphological biomarkers (microfossils of filamentous cyanobacteria). Energy dispersive X-ray Spectroscopy (EDS) analysis reveals that nitrogen is below the detectability level in most of the meteorite filaments as well as in Cambrian Trilobites and filaments of 2.7 Gya Archaean cyanobacteria from Karelia. The deficiency of nitrogen in the filaments and the total absence of sugars, of twelve of the life-critical protein amino acids, and two of the nucleobases of DNA and RNA provide clear and convincing evidence that these filaments are not modern biological contaminants. This paper reviews the chiral, chemical biomarkers morphological biomarkers and microfossils in carbonaceous meteorites. This paper reviews chiral and morphological biomarkers and discusses the missing nitrogen, sugars, protein amino acids, and nucleobases as "bio-discriminators" that exclude modern biological contaminants as a possible explanation for the permineralized cyanobacterial filaments found in the meteorites.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Richard B. Hoover "Chiral biomarkers and microfossils in carbonaceous meteorites", Proc. SPIE 7819, Instruments, Methods, and Missions for Astrobiology XIII, 781903 (7 September 2010); doi: 10.1117/12.863372; https://doi.org/10.1117/12.863372
PROCEEDINGS
15 PAGES


SHARE
Advertisement
Advertisement
RELATED CONTENT

Life is everywhere
Proceedings of SPIE (December 29 1999)
Bacterial utilization of L-sugars and D-amino acids
Proceedings of SPIE (September 13 2006)
Advances in laser-ablation-assisted processes
Proceedings of SPIE (January 29 2001)
Crystallographic image reconstruction problem
Proceedings of SPIE (November 08 1993)
Vibrations and stability of nucleotides: guanine
Proceedings of SPIE (April 28 2005)

Back to Top