Scientists may have unraveled a 40-year secret about how the Earth became warm enough to acquire a liquid ocean on its surface.
“The key was a phenomenon known as super-flashes, which are larger and stronger solar flares,” say NASA officials.
Computer models show that almost every day the flow of energy particles from the Sun compresses the magnetic bubble of the Earth and causes holes in the polar regions of the planet.
"These particles can then enter the atmosphere, triggering a cascade of chemical reactions that create an extremely powerful greenhouse gas, nitrous oxide, and also hydrogen cyanide," a study published in Nature Geoscience shows. "The earth has become warm enough for the existence of liquid water 4 billion years ago."
The first signs of microbial life appeared just at the same time.
Scientists have tried for decades to solve the paradox of the so-called “weak young Sun”, formulated by astronomer Carl Sagan and George Mullen in 1972. “He explains why the Earth finally warmed up under the less heated Sun,” writes Ramses Ramirez of Cornell University in a commentary on the study.
The new theory extrapolates data collected by the Kepler Space Telescope, whose main mission is to search for planets orbiting around Sun-like stars.
Temporary dips in the amount of light coming from the target stars can be caused by planets passing in front of the parent star. But changes can also be caused by other events, such as super-spikes.
"Kepler observed superflash of young stars resembling our Sun at a time when life originated on Earth ... We used them as proxy servers," astrophysicist Vladimir Ayrapetyan from NASA's Goddard Space Flight Center in Greenbelt, Maryland told Discovery News
Super-flashes turn out to be three times more powerful than the strongest flashes in modern history, for example, the so-called Carrington event in 1859, which gave birth to the Northern Lights far to the south.
"The earth is constantly under the threat of these powerful coronal mass ejections," said Hayrapetyan. Coronal emissions emit huge amounts of solar particles and electromagnetic radiation into space.
Ramirez will use data on atmospheric chemistry in another computer model to test Hayrapetyan’s theory.
"My goal is to calculate the resulting greenhouse effect from the projected gas concentrations and determine if they are enough to solve the problem of the weak young Sun," Ramirez said.
The study has not only implications for how life evolved on Earth, but also how our neighbor, Mars, developed.
"Our concept implies that the activities of the early Sun provided a window of opportunity for prebiotic life on Earth. The proposed model also redefines the conditions of habitability, not only in terms of the“ liquid water zone ”, but as a biogenic zone within which stellar energy flows are quite high , to ignite the reactive chemistry, which produces complex molecules necessary for life, "writes Hayrapetyan.
