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Joint JINR Seminar

29.03.2013
A Joint JINR Seminar will be held on 3 April 2013 at 3:00 pm in the Conference hall of the Bogoliubov Laboratory of Theoretical Physics. Speaker: Richard B. Hoover (University of Buckingham, United Kingdom and Athens State University, USA) "Evidence for Extraterrestrial Biomolecules, Water, and Indigenous Microfossils in Carbonaceous Chondrites".

Abstract
Carbonaceous chondrites are the most primitive of all known meteorites. These matrix-rich micro-regolith breccias contain carbon and represent a subgroup of stony meteorites that are of great  importance to cosmochemistry. These stones are thought to carry an unaltered pristine record of the chemistry of the proto-solar nebula. It has been known since 1834 that carbonaceous chondrites contain water. Although the water was initially believed to be a post arrival contaminant, the minerals in the stones exhibit extensive aqueous alteration and provide strong evidence for low temperature liquid water on the meteorite parent bodies. Over half a century ago, various scientists reported the detection of possible microfossils (organized elements, acritarchs, "blue-green algae" and magnetotactic bacteria) in the CI1 (Alais, Orgueil & Ivuna) and CM2 (Mighei & Murchison) carbonaceous chondrites. The stones were also found to contain a complex suite of life-critical biomolecules (chiral protein amino acids, purine and pyrimidine nucleobases, etc.) and biomolecular fossils such as pristane, phytane and porphyrins (diagenetic breakdown products of chlorophyll), long chain hydrocarbons and kerogen. Many of these biomolecules have never been produced in the laboratory by Miller-Urey of Fischer-Tropsch Synthesis or other abiotic production mechanisms. Nevertheless, these findings were attacked by critics and the post-arrival biological contamination hypothesis became widely accepted by the scientific community and the biological evidence was summarily dismissed.

During the past few decades, several researchers have obtained data that effectively invalidates the post-arrival bio-contamination hypothesis. Carbonaceous chondrites are now known to contain only 3 of the 5 nucleobases essential for life and only 8 (the most stable) of the 20 life-critical protein amino acids which are present in living  cell. Stable carbon isotope studies have established that these biomolecules indigenous and extraterrestrial. Living microorganisms could not possibly introduce only a subset of the biomolecules present in DNA, RNA and all proteins. Hence, contamination of these carbonaceous meteorites by recent microbes can be ruled out and the biomolecules are indicative of ancient extraterrestrial microbiological activity. This conclusion is supported by the independent detection in the U.S., U.K. and Russia of intact and recognizable microfossils of filamentous cyanobacteria, acritarchs, hystrichospheres, and diatoms in freshly fractured interior surfaces of meteorites. EDAX nitrogen data for many of these fossils is below the instrumental detection limit (<0.5% atomic) at levels consistent with those found in ancient (Pleistocene to Archaean) microbial remains. Many of these microfossils are permineralized and extinct life forms that are observed to be embedded in the meteorite rock matrix. Therefore, they could not possibly have invaded the stones after the meteorites were observed to fall. The biomolecular data will be discussed and recently obtained FESEM images and EDAX data for embedded microfossils will be presented. The well preserved and clearly recognizable microorganisms in carbonaceous meteorites are interpreted as indigenous remains of prokaryotic and eukaryotic microbiota and direct observational evidence for the existence of Extraterrestrial Life.