©Bomfleur, McLoughlin, Vajda
Cytological features in the Korsaröd fern fossil
When we send probes to other worlds (such as Mars) to look for evidence of past life, we are sending them to look for fossils.
Often times a fossil preserves some - but not all - of a once -living organism. Fine detail such as cellular structure are usually not well preserved owing to the time it takes for fossilization to begin and how far decomposition progresses before structures can be preserved. In a newly published paper, fossil ferns found in Sweden that are 180 million years old were preserved so rapidly that fine details inside individual cells were preserved.
With indications that Mars may have had periods in the past where it may have had habitable conditions on time frames on the order of hundreds of millions of years, this finding lends hope to the notion that if life has existed on Mars, that it might be preserved as fossils.
Full paper: Fossilized Nuclei and Chromosomes Reveal 180 Million Years of Genomic Stasis in Royal Ferns, Benjamin Bomfleur, Stephen McLoughlin, Vivi Vajda, Science
Abstract: "Rapidly permineralized fossils can provide exceptional insights into the evolution of life over geological time. Here, we present an exquisitely preserved, calcified stem of a royal fern (Osmundaceae) from Early Jurassic lahar deposits of Sweden in which authigenic mineral precipitation from hydrothermal brines occurred so rapidly that it preserved cytoplasm, cytosol granules, nuclei, and even chromosomes in various stages of cell division. Morphometric parameters of interphase nuclei match those of extant Osmundaceae, indicating that the genome size of these reputed "living fossils" has remained unchanged over at least 180 million years--a paramount example of evolutionary stasis."
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