When did Life Likely Emerge on Earth in an RNA-First Process?

TL;DR

The paper proposes a model suggesting that Earth's impact history created a window around 4.36 billion years ago when conditions favored the emergence of RNA, supported by geological and atmospheric evidence.

Contribution

It introduces a novel impact-based model linking Earth's impact history to the timing of RNA emergence, integrating physics, geology, and chemistry.

Findings

RNA formation most probable ~4.36 billion years ago

Impact event Moneta created a window for RNA synthesis

Atmospheric and geological conditions supported RNA precursors

Abstract

The widespread presence of ribonucleic acid (RNA) catalysts and cofactors in Earth's biosphere today suggests that RNA was the first biopolymer to support Darwinian evolution. However, most "path-hypotheses" to generate building blocks for RNA require reduced nitrogen-containing compounds not made in useful amounts in the CO2-N2-H2O atmospheres of the Hadean. We review models for Earth's impact history that invoke a single ~10^23 kg impactor (Moneta) to account for measured amounts of platinum, gold, and other siderophilic ("iron-loving") elements on the Earth and Moon. If it were the last sterilizing impactor, Moneta would have reduced the atmosphere but not its mantle, opening a "window of opportunity" for RNA synthesis, a period when RNA precursors rained from the atmosphere to land holding oxidized minerals that stabilize advanced RNA precursors and RNA. Surprisingly, this combination of physics, geology, and chemistry suggests a time when RNA formation was most probable, ~120 +/- 100 million years after Moneta's impact, or ~4.36 +/- 0.1 billion years ago. Uncertainties in this time are driven by uncertainties in rates of productive atmosphere loss and amounts of sub-aerial land.