Refined Chemical Conditions on Early Earth Determined the Possibility of Life's Emergence

A groundbreaking study conducted at ETH Zurich has recently redefined the specific chemical boundaries that allowed life to begin on Earth. Published in the prestigious journal Nature Astronomy, the research suggests that the mere presence of liquid water and temperate climates was insufficient for abiogenesis; instead, a precise concentration of oxygen within the planet's mantle during its formative stages approximately 4.6 billion years ago played a decisive role in making the world habitable.

The scientific team, featuring NOMIS–ETH fellow Craig Walton and Professor Maria Schönbachler from ETH Zurich’s Institute of Geochemistry and Petrology, utilized advanced computer simulations to demonstrate how the retention of life-sustaining elements is governed by oxygen levels. They found that the preservation of phosphorus—vital for DNA, RNA, and cellular energy—and nitrogen—essential for protein synthesis—within the mantle is extremely sensitive to oxygen levels during the period of core formation. Consequently, Walton and Schönbachler concluded that Earth developed within a unique chemical Goldilocks zone that facilitated the necessary biochemistry.

According to the modeling data, even slight deviations in oxygen levels during the planet's infancy would have been catastrophic for the potential of life. Had oxygen levels been marginally higher, nitrogen would have escaped into space; conversely, if levels were lower, phosphorus would have been sequestered within the planet's core, making it inaccessible for biological processes. Professor Schönbachler, whose expertise includes analyzing extraterrestrial samples from the Hayabusa2 and OSIRIS-Rex missions, noted that these geochemical constraints cast doubt on the habitability of other planets like Mars, which likely formed outside this narrow chemical window.

This research represents a significant paradigm shift in astrobiology, moving the focus from the traditional search for liquid water to a more sophisticated chemical filter involving early planetary oxygenation. While previous theories of abiogenesis often assumed a reducing atmosphere with minimal free oxygen, this new evidence points to the necessity of a perfectly balanced, intermediate oxygen level specifically during the moment of core accretion. Walton emphasizes that Earth’s capacity to harbor life is essentially the result of remarkable chemical luck rather than a common planetary occurrence.

The implications of these findings suggest that future searches for extraterrestrial life must account for the chemical composition of parent stars, as these stars influence the chemistry of the planets forming around them. This insight paves the way for new research initiatives like the ETH Zurich-led NCCR Genesis project, which integrates Earth sciences, chemistry, and biology to solve the mysteries of life's origins. Ultimately, the emergence of life requires more than just the existence of basic building blocks; it necessitates their preservation in an accessible form within a planet's mantle, which is a rare and fortunate geochemical coincidence.