‘Cosmic splash’ started life on Earth
Evidence has emerged that life began on our planet when meteorites crashed into ponds
The age-old theory that meteorites may have splashed down in small, warm ponds, bringing life to Earth some 4.1-billion-years ago has been lent greater credence thanks to an exciting new study.
Ben K.D. Pearce, an astrobiologist at McMaster University in Canada, says calculations performed by his team show that the space rocks could have delivered essential organics such as nucleotides into an early Earth environment. He says a combination of wet and dry cycles as water levels fell and rose would have bonded the basic molecular building blocks in the ponds' nutrient-rich broth.
This, Pearce adds, may have led to the formation of self-replicating ribonucleic acid, or RNA, which many scientists believe was the first kind of life on our planet. Such findings back Charles Darwin's theory, and they were based on evidence-based calculations, which drew upon aspects of chemistry, geology, biology and astrophysics. They took into account that life began when the Earth was still taking shape, and they were based on a period when there was no protective ozone and when continents were emerging from the oceans – all potential threats to the survival of the nucleotides.
According to the study, the conditions in thousands of ponds were more favourable to this process than in the oceans. It also concluded that the world would have been inhabited entirely by RNA-based life until DNA evolved.
“DNA is too complex to have been the first aspect of life to emerge,” says co-scientist Ralph Pudritz. “It had to start with something else, and that is RNA.”