Earth may have first offered conditions in which the chemistry that precedes life could persist around 4.33 billion years ago, according to a new computer simulation published in Nature Communications.
The team, led in part by Oleg Abramov of the Planetary Science Institute, modelled in three dimensions how impacts heated Earth's crust between 4.5 billion and 3.5 billion years ago. Large collisions could raise ground temperatures enough to destroy the fragile molecules involved in prebiotic chemistry; even regions that cooled were vulnerable to being heated again by a later strike.
The researchers asked whether conditions could support an early stage sometimes called the 'RNA world'. RNA can carry information and assist chemical reactions, and some scientists think it played a key role before life relied on DNA for heredity as it does today. For such molecules to form and interact, suitable conditions had to persist.
The model suggests this began around 4.4 billion years ago. As impacts became less disruptive, portions of Earth's shallow crust cooled and were never again heated above the study's temperature limit. Those stable regions grew over time: by 4.25 billion years ago they made up more than half the modelled crustal volume.
Impacts also helped. When a collision broke and heated rock, water could flow through it and form a hydrothermal system — an environment offering water, warmth and chemical energy. The study identifies a window where the two conditions overlapped: around 4.33 billion years ago, stable areas could persist while impact-created hydrothermal systems remained widespread.
The caveat is significant. The date is an estimate from a model, not evidence that life began then, and nobody yet knows where or when it actually did. The work suggests only that Earth offered lasting opportunities for life's earliest chemistry hundreds of millions of years after the planet formed.
