Microfossils, biomolecules and biominerals in carbonaceous meteorites: implications to the origin of life

摘要

Environmental and Field Emission Scanning Electron Microscopy (ESEM and FESEM) investigations haveshown that a wide variety of carbonaceous meteorites contain the remains of large filaments embedded withinfreshly fractured interior surfaces of the meteorite rock matrix. The filaments occur singly or in denseassemblages and mats and are often encased within carbon-rich, electron transparent sheaths. ElectronDispersive X-ray Spectroscopy (EDS) spot analysis and 2D X-Ray maps indicate the filaments rarely havedetectable nitrogen levels and exhibit elemental compositions consistent with that interpretation that of themeteorite rock matrix. Many of the meteorite filaments are exceptionally well-preserved and show evidenceof cells, cell-wall constrictions and specialized cells and processes for reproduction, nitrogen fixation,attachment and motility. Morphological and morphometric analyses permit many of the filaments to beassociated with morphotypes of known genera and species of known filamentous trichomic prokaryotes(cyanobacteria and sulfur bacteria). The presence in carbonaceous meteorites of diagenetic breakdownproducts of chlorophyll (pristane and phytane) along with indigenous and extraterrestrial chiral protein aminoacids, nucleobases and other life-critical biomolecules provides strong support to the hypothesis that thesefilaments represent the remains of cyanobacteria and other microorganisms that grew on the meteorite parentbody. The absence of other life-critical biomolecules in the meteorites and the lack of detectable levels ofnitrogen indicate the filaments died long ago and can not possibly represent modern microbial contaminantsthat entered the stones after they arrived on Earth. This paper presents new evidence for microfossils,biomolecules and biominerals in carbonaceous meteorites and considers the implications to some of the majorhypotheses for the Origin of Life.© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.