How did life on Earth begin? A new study suggests that the origin of life stems back to a young sun and the flares - as potent as a thousand trillion exploding atomic bombs - that it sent crashing into the planet around four billion years ago. This would explain how the Earth and its star, much colder at that time, came to be hospitable for life.
A team of researchers discovered that although the sun was much fainter than it is today around four billion years ago, it was also much more tempestuous. During that time, repeated super-flares likely threw nitrogen (N2) molecules into the atmosphere of Earth, causing the creation of nitrous oxide (N2O) and hydrogen cyanide, which creates amino acids, the building blocks of proteins, and thus life.
Although nitrogen is essential for all kinds of life, the form that existed in the atmosphere of primordial Earth was not likely reactive, meaning it would have needed to be converted into forms accessible for the creation of life. One way that this can happen is the presence of extremely high temperatures.
In the current study, the team examined telescopic observation of stars that closely resemble our sun in the first few hundred million years of its life and combined these results with models of the chemistry of the atmosphere of primordial Earth.
The team said that without greenhouse gases to trap the sun's heat, Earth would be a snowball. However, four million years ago it was a wet, warm planet that supported life, and the new model suggests that this is due to the N2O created by the sun's flares.
"Our model describes the 'cosmic' ingredient required to produce biological molecules of life," said Vladimir Airapetian of George Mason University and co-author of the study, adding that other planets that experienced similar events likely had similar outcomes.
"Geologic evidence suggests that Mars was also paradoxically warm and wet around the same time," said Ramses Ramirez of the Carl Sagan Institute who was not involved in the study. "The findings may have implications for the climates and potential biology of terrestrial exoplanets orbiting very young Sun-like stars, particularly stars with exceptionally high magnetic fluxes and very intense super stellar storms."
The findings were published in the May 23 issue of Nature Geoscience.
