A team of scientists from the United States and Japan has discovered traces of a series of ancient asteroids that struck Earth during the Archean Eon, which contributed to the planet’s inhospitable conditions for billions of years.
Earth’s landscape during the Archean Eon – (Photo: SwRI / Dan Durda / Simone Marchi).
According to Sci-News, when large asteroids or comets collide with young Earth, they release energy that melts and vaporizes materials in the Earth’s crust. The molten rock droplets that are ejected then condense, solidify, and fall back to Earth, creating scattered particles known as “impact glass” or “spherules.”
The recently published study in the scientific journal Nature Geoscience, led by Professor Nadja Drabon from the Department of Geological Sciences at Stanford University (USA), identified numerous thin and discrete layers filled with impact glass in the Earth’s crust, dating from 2.4 to 3.5 billion years ago.
According to Science Alert, this is evidence that during this period—part of the Archean Eon—Earth was continuously bombarded by “extraterrestrial forces.” Geological records indicate that from the beginning of the Archean Eon (around 4 billion years ago), the concentration of oxygen in the atmosphere began to increase, as the planet gradually balanced the processes of oxygen production and removal.
However, for billions of years thereafter, oxygen levels did not rise sufficiently to support life due to extraterrestrial impacts that slowed the evolution of the atmosphere. Objects larger than 10 kilometers in diameter were more than capable of consuming the scarce oxygen in the primordial atmosphere, essentially “burning” it almost completely during the collisions.
Therefore, even though throughout that period, the first organisms on the planet, such as cyanobacteria, struggled to produce oxygen, it was still insufficient to generate levels adequate for life to evolve to higher forms. “Over time, collisions became less frequent and smaller, allowing Earth’s oxygen concentration to change significantly. After the Great Oxidation Event, Earth gradually began its transformation into the planet we know today.” – the authors explained.
