Bathing in lethal ultraviolet (UV) rays ten times stronger than those on Earth today, tiny organisms continue to survive and evolve over billions of years – they are the ancient ancestors of all species.
This is the level of radiation that is believed to be completely unsuitable for life, which many exoplanets are currently subjected to. However, this assumption may be incorrect, according to shocking conclusions from research published in the journal Royal Society Open Science.
The difference between Earth 2 billion years ago (left) and present-day Earth shows it was once drenched in “alien-like” harsh conditions – (Image: Royal Society Open Science)
According to Dr. Gregory Cooke from the University of Leeds and his colleagues, our Earth was once like that. Their computer simulations of early Earth over the past 2.4 billion years reveal that Earth was a harsh world, drenched in solar radiation, receiving UV rays ten times more than today.
With such levels of UV, modern organisms would perish. But it seems that primitive life forms did not. Previous studies have indicated that life on Earth first emerged over 4 billion years ago, with some research suggesting a figure as high as 4.3 billion years.
However, at least 2 to 2.4 billion years ago, Earth remained a place resembling the alien worlds we have assumed to be uninhabitable.
The cause of this lethal UV radiation is the atmosphere with low oxygen content, and the primitive ozone layer was insufficient to shield against harmful UV rays affecting the surface, according to Phys.org.
The research team suggests that this could lead to “fascinating consequences” for the evolutionary process of life.
This discovery also opens a new avenue for the search for extraterrestrial life, as relying on the conditions that modern Earth life requires to survive seems too stringent to assess whether a planet is habitable.
