Biogenicity analysis of stromatolite structures.

摘要

The origin of stromatolites (laminated, dome-shaped geologic structures thought to constitute some of the oldest fossils on Earth) is controversial. Stromatolites are now known to form via biologic and abiologic processes. Separating the two can improve our understanding of the evolution of life on Earth (and potentially other planets). Four information-theoretic image features (gzip compression, PNG compression, entropy, and Wold energy ratio) are proposed to help differentiate biogenic from abiotic samples. A biogenic separability metric is defined to permit a quantitative assessment of these features. The most effective feature was the PNG compression ratio, which provided good biogenic separability for macroscopic and microscopic views of stromatolites. Increasing the size of the analysis sub-window and/or increasing magnification also improved separability. While conclusive judgments about biogenicity are unlikely to be made solely from these features, they can provide a "first cut" estimate of the importance of a follow-up search for other biosignatures.