LIFE

Where Life May Have Started

~4.2 billion years ago (setting debated)

Hadean

On the deep sea floor, seawater seeps into certain dark rocks and turns them into serpentine, soft and green; the reaction gives off hydrogen. Where the warm alkaline fluid wells back up into what was then a mildly acidic ocean, it builds chimneys shot through with a labyrinth of tiny pores. Across each of their thin mineral walls stands a difference in acidity: an electrical gradient of the same polarity, and of comparable strength, as the one every living cell still uses to power itself.

Why it matters

Of all the birthplaces proposed for life, this is the one where the rock itself performs, without any biology, the feat every living cell must otherwise manage on its own: holding a usable charge between an inside and an outside.

Dating & uncertaintyDisputed

The date here is borrowed, not measured. Sea floor that old was swallowed back into the mantle long ago, so no trace of the first vents can survive; the event sits near 4.2 billion years because that is where genetics places LUCA, the ancestor of all current life, and if life began in these chimneys their chemistry had to be running by then. This card and LUCA's therefore share one clock rather than carrying two independent dates. The setting is argued as well: the rival school starts life in warm ponds at the surface instead.

Sources

1. Sojo et al. (2016), Astrobiology · The origin of life in alkaline hydrothermal vents
2. Lane (2017), BioEssays · Proton gradients at the origin of life
3. Schwander et al. (2023), Frontiers in Microbiology · Serpentinization as the source of energy, electrons, organics, catalysts, nutrients and pH gradients for the origin of LUCA and life

Earth history as one day

01:47:5022 h 12 min before midnight

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