This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Conditions on early Earth may have become stable enough to sustain the chemistry associated with the origins of life around 4.33 billion years ago, according to new research co-led by Planetary Science Institute senior scientist Oleg Abramov. The study, published in Nature Communications, uses a three-dimensional computer model to reconstruct how asteroid, comet and planetesimal impacts heated Earth's crust between 4.5 billion and 3.5 billion years ago.
Results suggest that these frequent global sterilization events continued until about 4.4 billion years ago. After that, more stable environments emerged where RNA and other molecules important to life could survive. "We used a different approach than previous studies, which were based on geochemical modeling, biomolecular analyses and models of early atmospheric chemistry," Abramov said.
"We constructed an impact bombardment model constrained by observables such as the lunar cratering record and highly siderophile elements in the upper mantle. We examined both detrimental effects of impacts, such as temperature-induced degradation of key biomolecules, and effects conducive to life, such as generation of hydrothermal systems. "These criteria point to the Earth becoming suitable for an early stage of life between 4.4 billion and 4.3 billion years ago, with optimal conditions at approximately 4.33 billion years ago." The research team was specifically interested in the "RNA World," a proposed early stage in the history of life before DNA took on its modern role.
RNA holds genetic information and can perform some of the chemical work needed for replication, making it a leading candidate for an early biological system. For an RNA World to develop, though, molecules would need time to form, remain stable and interact. Early Earth did not provide that stability.
The planet was continuously hit by asteroids, comets and leftover planetesimals whose impacts created an inhospitable environment. The new model outlined in the paper follows what happened as that bombardment gradually eased. Abramov and his colleagues simulated how impacts heated Earth's crust over 1 billion years, then compared those temperatures with the limits at which RNA and other molecules important to life can remain stable.
They also looked at different estimates for the amount of material that struck Earth during this period. Their simulations show a shift beginning around 4.4 billion years ago. Before then, an area that had cooled enough for prebiotic chemistry could still be heated again by a later impact.
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