The beginning of life on Earth might have been caused by one of the most violent phenomena our Sun can produce: superflares.
Although the younger Sun was dimmer back then about four billion years ago, it was a lot more active, emitting frequent and intense solar storms, according to a team of researchers from NASA’s Goddard Space Flight Center. The Sun showered the Earth in energetic particles that broke molecules apart, possibly leading to the formation of compounds that are essential for life. Their research is published in Nature Geoscience.
While these findings were obtained thanks to computer simulations, they are built on discoveries by NASA’s Kepler Space Observatory. The planet-hunting telescope has discovered several baby stars that look similar to what our Sun might have once been. These young objects, only a few million years old, produce up to 10 superflares per day, compared to the one per century of the Sun today.
“Back then, Earth received only about 70 percent of the energy from the Sun than it does today,” said Vladimir Airapetian, lead author of the paper, in a statement. “That means Earth should have been an icy ball. Instead, geological evidence says it was a warm globe with liquid water. We call this the Faint Young Sun Paradox. Our new research shows that solar storms could have been central to warming Earth.”
Four billion years ago, Earth’s magnetic field was much weaker and particles could more easily reach the atmospheric gas. According to the paper, aurorae would have been visible all the way to the 33rd parallel, about modern-day South Carolina.
The solar particles would hit the gas in the atmosphere, breaking apart carbon dioxide, methane, and molecular nitrogen. This would lead to the formation of new molecules such as hydrogen cyanide, which is believed to be a precursor to life molecules, and nitrogen oxide.
The production of nitrogen oxide is the most interesting point in the research. Nitrogen oxide is an incredible greenhouse gas, about 300 times more powerful than CO2. The study indicates that with just 1 percent as much nitrous oxide as carbon dioxide in the early atmosphere, the Earth would have been warm enough to have liquid water on its surface.
Water and the right chemicals are certainly a necessary condition for the formation of life, but this research shows that stellar evolution is a major player in the making of life, and it should be taken into account when we look for life elsewhere in the cosmos.