Pyrite Life
The iron-sulfur world experiments are aimed at long reaction cascades and catalytic feedback (metabolism) from the start. The maxim of the iron-sulfur world theory should therefore be “order out of order out of order.” ~ Günter Wächtershäuser
German organic chemist Günter Wächtershäuser developed the iron-sulfur world theory in the late 1980s, arguing that metabolism arose as a prerequisite to replication. Wächtershäuser and others contend that organic compounds emerged on the surface of pyrite in seafloor hydrothermal vents.
Pyrite is a mineral comprising iron and sulfur (FeS2), called fool’s gold because prospectors sometimes mistook its glimmer for gold. Pyrite is both hoary and ubiquitous. The mineral is found everywhere, even in the oldest sedimentary rocks. The chimneys of hydrothermal vents largely consist of pyrite.
While its location may appear fortuitous, Wächtershäuser’s construction was not only for geochemical reasons. On the bottom line is energy.
Pyrite is synthesized from hydrogen sulfide (H2S) and an iron salt (FeS) – abundant ingredients on primordial Earth.
H2S + FeS → FeS2 + H2 + energy
Besides releasing chemical energy from which autotrophic life may have originated, hydrogen released in the production of pyrite provides the reducing power needed to synthesize organic compounds from carbon dioxide (CO2).
Wächtershäuser developed a compelling story, but the devils in the details resulted in numerous objections by others in the field: complaints about unanswered questions concerning critical facets that are fundamental biochemical mechanisms.
Foremost, Wächtershäuser’s model requires a bootstrap technique to get from fool’s gold to life. That bootstrap is some chemical scaffolding acting as a protocell; a concept advanced by Scottish organic chemist Graham Cairns-Smith. Given a plausible scenario for a protocell, Wächtershäuser’s pyrite-pulled chemoautotrophic model appears redeemed.
