Researchers Identify the Moment Life’s Conditions Emerged on Earth

By modeling the thermal environment of Earth during the Hadean eon, which was shaped by meteorite impacts, an international research team—including researchers from the HUN-REN Research Center for Astronomy and Earth Sciences (HUN-REN CSFK)—has determined the emergence of the sustained favorable conditions necessary for the origin of life.

The interdisciplinary research, led by Oleg Abramov, and drawing on findings from biology, geology, chemistry, and astronomy—examined when and where conditions may have become permanently favorable for the emergence of life, particularly the RNA world, in the early Hadean crust.

As they wrote,

the RNA world (and thus life) likely began in the Hadean, which was the first eon on the geological time scale of Earth’s history, spanning from the planet’s formation 4.6 billion years ago to the beginning of the Archean, approximately 4.0 billion years ago.

The early part of this period, in particular, was characterized by impacts from comets, surviving planetesimals, and asteroids. The giant impact that led to the formation of the Moon likely occurred roughly 4.51 billion years ago, setting a strict limit on the emergence of life, as it resulted in the complete melting (and thus sterilization) of the crust.

Studying the frequency of impacts and the gradually decreasing temperature of the mantle provides insight into the environment of the Hadean Earth; this may be the first step toward understanding the origin of life.

Oleg Abramov and his team—researchers from the Bavarian Geosciences Institute (Bayerisches Geoinstitut), HUN-REN CSFK, and the Polish Academy of Sciences (Polska Akademia Nauk)—focused primarily on the role of temperature. They attempted to determine the point in time when prebiotic chemistry not only became possible but could also be sustained long enough for an RNA world to form and evolve.

The main focus was on how the volume of the Hadean crust—which would never again be sterilized by impacts—changed:

that is, if life arose within it, it could survive, evolve, and spread. Another important question was whether these impacts could also have a positive effect on the emergence of life.

The results of the research suggest that 4.4 billion years ago, Earth was not yet suitable for sustained biochemistry. Later, however, the meteorite bombardment subsided, and high-energy hydrothermal environments could have formed that were optimal for the emergence of life. These may have served as energy-rich oases for organic synthesis, and by 4.35 billion years ago, the stable preservation of biomolecules—including RNA, DNA, and RNA-peptide complexes—had become likely. This period may have represented the optimal point for the emergence of life and the starting point of the evolution that ultimately led to the Last Universal Common Ancestor (LUCA).

LUCA is the lowest common point on the family tree of life on Earth, from which all organisms living today—including bacteria, plants, animals, and humans—evolved.

Since the most recent molecular clock analyses date the emergence of LUCA to between 4.09 and 4.33 billion years ago, the research highlights that only about 150 million years elapsed between the first RNA-based life forms and the emergence of complex systems similar to modern bacteria.

Via MTI; Featured photo: Pexels

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