The faint young Sun paradox was originally posed by Carl Sagan. Primitive life existed on Earth 4 billion years ago. But back then the Sun was much fainter, so too cold to supply the heat for life on Earth. So we need a big greenhouse effect to warm things up. The trouble with that solution is that it requires 300 time more carbon dioxide than we have today, which would make the Earth to acidic to allow life to happen. This new research poses a new answer – large frequent solar flares from an angry young Sun result in Nitrous Oxide in the Earth’s early atmosphere. This gas is a much more efficient greenhouse gas, so it only requires a small amount to supply the extra heat. As a bonus, this process that creates the Nitrous Oxide also creates abundant hydrocarbons required to cook up life.
This raises the possibility of life being much more abundant in the Universe than we had thought previously. If young stars can produce flares like our Sun, then the habitable zone (the not-too-far, yet not-to-close distance from the star) is much, much larger and exists for a much, much longer time than anyone has considered.