Four billion years ago, the Sun shone with only about three-quarters of its intensity today. Consequently, Earth should have been a cold frozen planet back then, but geological evidence indicates that it was already quite warm enough to support liquid water – and the basic molecular building blocks of life. This apparent paradox (called the “Faint Young Sun Paradox”) has baffled scientists. How can it be resolved? Now, a group of NASA researchers is focusing on the possibility that massive solar eruptions of the type we experience only once every century or so in our time were happening as many as 10 times a day in those billions of years past. If the hypothesis is correct, researchers would have a valuable path not only to understanding the earliest evolution of life on Earth but also to searching for the right conditions for its genesis on exoplanets in the habitable zones of myriad stars in our Milky Way galaxy and beyond.
Sun’s adolescent storms may have been key to life on Earth