LIFE × ATMOSPHERE

The First Methane Makers

~3.46 billion years ago

Archean · Paleoarchean

Microbes that live on hydrogen and carbon dioxide alone, and give off methane, are among the simplest forms of life we know. Bubbles of their gas lie trapped in Australian rocks three and a half billion years old.

Why it matters

Their methane is the leading candidate for what kept the planet warm under a Sun a fifth too faint. If so, organisms too small to see were already setting the temperature of a world.

Dating & uncertaintyDisputed

Methane trapped in 3.46-billion-year-old hydrothermal minerals carries a carbon signature that, as far as anyone knows, only life produces. Molecular clocks have been used to push methanogens back further still, and that use of clocks has been criticised in print for reflecting its own assumptions more than the data.

Sources

1. Ueno et al. (2006), Nature · Evidence from fluid inclusions for microbial methanogenesis in the early Archaean era
2. Roger & Susko (2018), Nature Ecology & Evolution · Molecular clocks provide little information to date methanogenic Archaea
3. Catling & Zahnle (2020), Science Advances · The Archean atmosphere

Earth history as one day

05:42:3318 h 17 min before midnight

if Earth’s 4.54 billion years were compressed into a single day