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4273-35

Evidence for Biomarkers and Microfossils in
Ancient Rocks and Meteorites

by

Richard B. Hoover

and

Alexei Yu. Rozanov

 

 

Abstract

The detection by McKay et al.1 of chemical biomarkers and possible microfossils in the ancient Mars meteorite  (ALH84001) enhanced interest in the possibility of microbial life on other bodies of the Solar System and triggered the development of the rapidly emerging field of Astrobiology.  Astrobiologists are now seeking to develop conclusive methods  to recognize biomarkers and bacterial microfossils as well as understand the spatial, temporal, environmental and chemical  limitations of microbial extremophiles.  Seeking additional evidence of possible microfossils in ancient terrestrial rocks and  meteorites, independent (and later collaborative) investigations were carried out in the United States and Russia using the  SEM, Environmental Scanning Electron Microscope (ESEM), and Field Emission Scanning Electron Microscope (FESEM).  In-situ investigations of freshly broken carbonaceous chondrites have shown the presence of a large number of complex  microstructures that appear to be lithified microbial forms.  Many of the forms we have found in carbonaceous meteorites are much larger than the possible nannofossils reported from the Allen Hills meteorite. Energy Dispersive Spectroscopy (EDS)  and Link microprobe analysis shows the possible microfossils have a distribution of chemical elements characteristic of the  meteorite rock matrix, although many exhibit a superimposed carbon enhancement.  The mineralized bodies encountered  embedded in the rock matrix of freshly fractured meteoritic surfaces can not be easily dismissed as recent surface  contaminants.  Many of the forms found in-situ in the Murchison, Efremovka, and Orgueil carbonaceous meteorites are  strikingly similar to microfossils of coccoid bacteria, cyanobacteria and fungi such as we have found in the Cambrian  phosphorites of Khubsugul, Mongolia and high carbon Phanerozoic and Precambrian rocks of the Siberian and Russian  Platforms.  This paper presents SEM images of microfossils that exhibit the characteristics of distinct stages of microbial life  cycles of Nostocacean cyanobacteria (including trichomes, spores, and hormogonia) and ecological systems similar to  those found in permafrost and cryoconite communities of Antarctica and Siberia.

Keywords

Biomarkers, Meteorites, Carbonaceous Chondrites; Astrobiology; Extremophiles, Microfossils.

 

  • The paper (author Web site)

 

Principal Author Biography

Richard B. Hoover is President of SPIE-The International Society for Optical Engineering.  He is Astrobiology Group Leader in the Space Science Department of the NASA Marshall Space Flight Center.  His previous research involved the development of X-ray Microscopes and Telescopes using normal incidence multilayer x-ray mirrors.  During the past three decades, he has conducted extensive investigations of microorganisms and siliceous microfossils.  Richard Hoover is Internationally known for his work on diatoms.  At the invitation of the Royal Zoological Society of Antwerp, Belgium, he conducted the Inventory of the diatom collections of the Henri van Heurck Museum.  He has written numerous articles and books on diatoms and micropaleontology.  His diatom photomicrographs and micromounts were exhibited at the Smithsonian Museum of Natural History and his article "Those Marvelous Myriad Diatoms" appeared in National Geographic in June, 1979.  As a Co-Investigator in the NASA Astrobiology Institute, he has studied morphological biomarkers and microfossils in ancient rocks and meteorites.  In January, 2000, Richard Hoover served as Scientific Team Leader of the Antarctica 2000 Expedition to collect meteorites and microorganisms from the blue ice in the Thiel Mountains of Antarctica and snow from the South Pole.  He collected permafrost microbiota from Alaska and Siberia and has investigated ancient microbiota cryopreserved in deep-ice cores from Vostok, Antarctica.

Principal Author Affiliation

Astrobiology Group Leader
Space Sciences Directorate/SD50
George C. Marshall Space Flight Center,
Huntsville, AL 35812
USA
Tel: 
Fax: 
Email: Richard.Hoover@msfc.nasa.gov

 

Secondary Author Affiliation

Director, Paleontological Institute,
Russian Academy of Sciences
Moscow,
Russia    

 

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