Powerful coronal mass ejection events from the young Sun may have provided the crucial energy needed to warm early Earth, according to a team of researchers led by Dr. Vladimir Airapetian of NASA’s Goddard Space Flight Center.
Artist’s concept of the active young Sun 4 billion years ago. Its energy may have aided in creating molecules in the atmosphere of early Earth that allowed it to warm up enough to incubate life. Image credit: NASA / GSFC / CIL.
“Back then, Earth received only about 70 percent of the energy from the Sun than it does today. That means Earth should have been an icy ball. Instead, geological evidence says it was a warm globe with liquid water,” Dr. Airapetian said.
“We call this the Faint Young Sun Paradox,” he added.
“Our new research shows that solar storms could have been central to warming Earth.”
NASA’s Kepler space telescope discovered stars that resemble our Sun about a few million years after its birth.
The data showed many examples of what are called ‘superflares’ — giant explosions so rare today that we only experience them once every 100 years or so.
Yet the Kepler data also show these youngsters producing as many as ten superflares a day.
While the Sun still produces flares and coronal mass ejections, they are not so frequent or intense. What’s more, Earth today has a strong magnetic field that helps keep the bulk of the energy from such space weather from reaching the planet.
However, early Earth had a weaker magnetic field, with a much wider footprint near the poles.
“Our calculations show that you would have regularly seen auroras all the way down in South Carolina,” Dr. Airapetian said.
“And as the particles from the space weather traveled down the magnetic field lines, they would have slammed into abundant nitrogen molecules in the atmosphere. Changing the atmosphere’s chemistry turns out to have made all the difference for life on Earth.”
The atmosphere of young Earth was also different than it is now: molecular nitrogen made up 90% of the atmosphere, compared to only 78% today. As energetic particles slammed into these nitrogen molecules, the impact broke them up into individual nitrogen atoms. They, in turn, collided with carbon dioxide, separating those molecules into carbon monoxide and oxygen.
The free-floating nitrogen and oxygen combined into nitrous oxide, which is a powerful greenhouse gas. When it comes to warming the atmosphere, nitrous oxide is some 300 times more powerful than carbon dioxide.
The teams’ calculations show that if the early atmosphere housed less than 1% as much nitrous oxide as it did carbon dioxide, it would warm the planet enough for liquid water to exist.
This constant influx of solar particles to early Earth may have done more than just warm the atmosphere, it may also have provided the energy needed to make complex chemicals.
The research is published in the journal Nature Geoscience.
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V.S. Airapetian et al. Prebiotic chemistry and atmospheric warming of early Earth by an active young Sun. Nature Geoscience, published online May 23, 2016; doi: 10.1038/ngeo2719
