What appear to be biochemical processes may be a natural feature of geology

Experimental result & possible mechanisms

• Sterilized soils still emit CO₂ and show Krebs‑cycle–like chemistry, suggesting some “biochemical” reactions can persist without living cells.
• One line of explanation: residual enzymes and their fragments survive killing and continue to catalyze reactions extracellularly, especially small active sites (e.g., Fe‑S clusters) that resemble mineral fragments.
• Another: purely abiotic catalysis by minerals, possibly mimicking metabolic pathways, though direct evidence is still lacking.
• Commenters note biochemists long ago showed metabolism-like processes in cell‑free extracts (e.g., ground yeast) and point to enzyme-driven degradation in foods like UHT milk.

Skepticism & methodological concerns

• Several question whether this is “new”: oxidation of organic carbon at low temperatures is known (e.g., coal self‑heating and CO₂ release).
• Critics ask where the complex organics come from if the process is claimed to be geological: soil is already highly biological, so starting with it may confound results.
• Some suggest repeating experiments with clearly abiotic starting material (granite dust, extraterrestrial regolith analogs) to validate a truly geological mechanism.
• Others worry about undetected extremophiles surviving sterilization and generating CO₂.

Implications for Mars and life detection

• If nonliving soils can produce metabolic‑like signatures, Mars experiments that look only for CO₂ or similar products might get false positives.
• Discussion branches into how to distinguish biotic from abiotic organics, e.g.,
  • distribution of amino acids (simple vs complex),
  • chirality (racemic vs single‑handed mixtures).
• Some argue these biosignatures could still differentiate life from chemistry, though alien life might not share Earth’s specific choices.

Origins of life & geochemistry

• Multiple comments connect this to theories where geochemistry “bootstraps” biochemistry, e.g., hydrothermal or alkaline vents creating energy gradients and catalyzing organics.
• Long exchange on likely universal roles of simple amino acids, sulfur and phosphorus chemistry, nitrogen scarcity, thioesters vs phosphates, and pre‑RNA metabolic networks.
• One view: RNA replication likely appeared on top of an existing metabolic network; early “hard‑wired” life without nucleic acids is considered plausible.

Broader perspectives

• Earth is likened to a vast “chemical computer” exploring configurations that accelerate entropy production, with life as one such emergent accelerator.
• Many expect simple life to be common but complex, eukaryote‑like life to be extremely rare, given how long it took to arise here and how quickly any new life would be outcompeted.