Biosignatures in Deep Time

Dear Colleagues,

Life probably appeared on Earth 4 billion years ago. Unfortunately, studying fossils dating from this time to understand the origin and early evolution of life is hampered by geological and biological processes. In particular, metamorphism, plate tectonics, and crustal recycling are responsible for the degradation or disappearance of most of the oldest fossils. Moreover, when looking back into the past, the presence of large organisms decreases with time, and for most of Earth’s history, the biosphere is only composed of microbes. While the biogenicity of fossilized complex organisms is relatively easy to demonstrate, the biotic origin of microbial remains is less obvious, and even when preserved, morphology alone is generally not sufficient. Demonstrating the biotic origin of microbial remains in deep time must be based on a network of congruent indications, i.e., the detection of several possible biosignatures in agreement with their present and ancient geological context.

This Special Issue focuses on corroborative biosignatures and bio-indicators that allow demonstration of the biogenicity of ancient microbial remains from the kilometer to nanometer scale. We are thus particularly looking for contributions based on correlative multiscalar and multimodal approaches.

Dr. Frédéric Foucher
Dr. Barbara Cavalazzi
Guest Editors

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• Precambrian
• Microfossils
• Biosignatures
• Early life
• Multiscale approaches
• Multimodal approaches
• Correlative microscopy

• Tracking the Deep Biosphere through Time in Geosciences (8 articles)
• Terra Incognita—Microbial Processes and Interactions in the Deep Biosphere in Geosciences (4 articles)