Microfossils from the Paleoarchean Eon are the oldest known evidence of life. Despite their significance in understanding the history of life on Earth, any interpretation of the nature of these […]
Archaean
Posted inBiogeochemical Cycles & Geobiology, Biophysics, Biosignatures & Paleobiology, Origin & Evolution of Life, Status Report
Did Iron Suppress Eukaryote Emergence and Early Radiation?
The last eukaryotic common ancestor (LECA) is widely thought to have been an oxygen-respiring organism, arising through endosymbiosis when a free-living bacterium became the mitochondrion.
![The multiple roles of methanogens in the modern-day carbon cycle. Processes shown in red contribute to greenhouse gas production. Part of the methane is removed through microbial methane oxidation (A)MO and photochemical reactions, where e is a generic electron donor (e.g., arsenate or sulfate) that is reduced to eH. Processes depicted in green sequester CO2, storing it long-term as carbonates. The size of the arrows relates to the relative biogeochemical importance of the process. The metabolic activity of methanogens may locally alter pH and produce copious amounts of EPS (seen as a veil surrounding the cells in the microphotograph (yellow arrow)). These EPS bind cations (e.g., Ca, Mg) and act as nucleation site, while elevated pH enhances the carbonate precipitation in microbial mats [196]. This contribution by methanogens may ultimately produce microbialites [183] -- preprints.org](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/01/Methanogens-Through-Geological.png?resize=1200%2C720&ssl=1)
Posted inBiosignatures & Paleobiology, Fossils & Paleontology, Gaia - Planetary Perspectives, Habitable Zones, Microbiology & Virology, Origin & Evolution of Life, Status Report
Methanogens Through Geological Time And Space: Impact On Planetary Evolution and Significance For Life Beyond Earth
Methanogens, also known as methanogenic archaea, are among the most ancient and widespread microorganisms, despite their particular requirements for growth. These oxygen-sensitive microorganisms have impacted climate and biogeochemical cycles throughout […]
Posted inBiosignatures & Paleobiology, Genomics, Proteomics, Bioinformatics, Microbiology & Virology, Origin & Evolution of Life, Status Report
Did Iron Suppress Eukaryote Emergence and Early Radiation?
The last eukaryotic common ancestor (LECA) is widely thought to have been an oxygen-respiring organism, arising through endosymbiosis when a free-living bacterium became the mitochondrion.
Posted inAtmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Mapping, Geodesy, Cartography, Bathymetry, Status Report, Water/Hycean Worlds & Oceanography
Transient Marine Bottom Water Oxygenation On Continental Shelves By 2.65 Billion Years AgoNature Geoscience
A growing body of evidence suggests that molecular oxygen (O2) accumulated in some shallow marine environments beneath the effectively anoxic Archaean atmosphere 4.0 to 2.5 billion years (Ga) ago.