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Project Progress

During this past year, results from this project have established the means to correlate biological cellular morphology with biological organic chemistry — a long-sought but technically difficult advance. Direct measurements of microfossils in situ have yielded new evidence by which to discriminate between true fossils and pseudofossil look-alikes and, thereby, a significantly firmer basis by which to evaluate putative evidence of ancient life on Earth.

Specifically, two papers published this past year present results of development and first application of laser-Raman imagery to exceedingly ancient microscopic fossils (3,375 and 3,465 Myr old). The spectra establish the carbonaceous (kerogenous) composition of these microscopic objects and demonstrate the usefulness of this new technique for eludication of the biogenicity of minute fossil-like bodies of putative biological origin (Schopf et al., 2002). Atomic force microscopy (AFM) has also been applied to what appear to be ancient microscopic fossils (650 Ma old). The AFM study not only established the carbonaceous (kerogenous) composition of these objects but also demonstrated the usefulness of this novel technique (as applied here) for establishing the nanometer-scale structure of the organic matter (kerogen) comprising these objects, data that also provide means to discriminate between true biological fossils and mineralic “look-alikes” (Schopf et al., 2002). Both laser-Raman spectroscopy and AFM are well established techniques but are relatively new as tools for investigating the biogenicity of putative ancient fossil materials. Both provide means for one-to-one correlation of fine structural morphology with chemical composition. Both provide new insight into the chemical makeup of ancient microscopic fossils. Both seem certain to be applied to any putative fossils or fossil-like objects detected in rock samples to be returned from Mars.

Based on the work completed this year, studies are underway that are designed to develop means to: (1) map optically — at a micron-level scale and in three dimensions — individual microscopic fossils (by use of new digitized, computer-aided techniques); (2) correlate such optically discernable micron-scale morphologies with chemical composition by mapping chemically, in three dimensions, individual microscopic fossils using digitized Raman images and computer-aided techniques; and (3) use Raman spectroscopy/imagery of ancient carbonaceous matter to develop a geologically useful pre-metamorphic low-temperature (<250°C) paleothermometer that will aid in establishing the degree of preservation of ancient biogenic materials.