The first building blocks of life on Earth may have formed as a result of eruptions from the Sun, a new study finds.
A series of chemical experiments show how solar particles, colliding with gases in Earth’s early atmosphere, can form amino acids and carboxylic acids, the basic building blocks of proteins and organic life. The findings were published in the journal Life.
To understand the origins of life, many scientists try to explain how amino acids, the raw materials from which proteins and all cellular life, were formed. The best-known proposal originated in the late 1800s as scientists speculated that life might have begun in a “warm little pond”: A soup of chemicals, energized by lightning, heat, and other energy sources, that could mix together in concentrated amounts to form organic molecules.
In 1953, Stanley Miller of the University of Chicago tried to recreate these primordial conditions in the lab. Miller filled a closed chamber with methane, ammonia, water, and molecular hydrogen – gases thought to be prevalent in Earth’s early atmosphere – and repeatedly ignited an electrical spark to simulate lightning. A week later, Miller and his graduate advisor Harold Urey analyzed the chamber’s contents and found that 20 different amino acids had formed.
“That was a big revelation,” said Vladimir Airapetian, a stellar astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “From the basic components of early Earth’s atmosphere, you can synthesize these complex organic molecules,” added the co-author of the new paper.
But the last 70 years have complicated this interpretation. Scientists now believe ammonia (NH3) and methane (CH4) were far less abundant; instead, Earth’s air was filled with carbon dioxide (CO2) and molecular nitrogen (N2), which require more energy to break down. These gases can still yield amino acids, but in greatly reduced quantities.
Seeking alternative energy sources, some scientists pointed to shockwaves from incoming meteors. Others cited solar ultraviolet radiation. Airapetian, using data from NASA’s Kepler mission, pointed to a new idea: energetic particles from the Sun.
Kepler observed far-off stars at different stages in their lifecycle, but its data provides hints about the Sun’s past. In 2016, Airapetian published a study suggesting that during Earth’s first 100 million years, the Sun was about 30 percent dimmer. But solar “superflares” – powerful eruptions that occur only once every 100 years – would have erupted once every 3-10 days. These superflares launch near-light speed particles that would regularly collide with the atmosphere, kickstarting chemical reactions.
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