A new study shows that the first building blocks of life on Earth may have been formed by explosions from our Sun. A series of chemical experiments show how when solar particles collided with gases in Earth’s early atmosphere, they were able to 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 origin of life, many scientists are trying to explain how amino acids, raw materials, proteins, and all cellular life came to be. The most famous suggestion came in the late 1800s, when scientists suggested that life might have originated in a “warm little pond”: a water of chemicals fueled by lightning, heat, and other energy sources that can mix in concentrated amounts to form organic molecules.

In 1953 Stanley Miller of the University of Chicago tried to reproduce these original conditions in the laboratory. Miller filled a sealed chamber with methane, ammonia, water, and molecular hydrogen—gases believed to be common in Earth’s early atmosphere—and repeatedly ignited an electric spark to simulate lightning. A week later, Miller and his graduate advisor, Harold Urey, analyzed the contents of the chamber and found that 20 different amino acids were formed.

“It was a great discovery,” said Volodymyr Hayrapetyan, a stellar astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and co-author of the new paper. “These complex organic molecules could be synthesized from key components of the early Earth’s atmosphere.”

But the last 70 years have complicated this interpretation. Scientists now believe there is much less ammonia (NH3) and methane (CH4); instead, Earth’s air was filled with carbon dioxide (CO2) and molecular nitrogen (N2), which required more energy to break down. These gases can still yield amino acids, but in greatly reduced amounts.

Some scientists seeking alternative energy sources have pointed to shock waves from incoming meteorites. Others cited the sun’s ultraviolet radiation. Using data from NASA’s Kepler mission, Airapetian pointed to a new idea: energetic particles from our sun.

Kepler has observed distant stars at various stages of their life cycles, but their data provides clues about our Sun’s past. In 2016, Airapetian published a study that found that the Sun was about 30% dimmer in the first 100 million years of Earth’s existence. But solar “super-bursts” – powerful eruptions we only see every 100 years today – would erupt every 3 to 10 days. These superflares throw particles near the speed of light that regularly collide with our atmosphere and trigger chemical reactions.

“As soon as I published this article, a team from Yokohama National University in Japan contacted me,” said Hayrapetyan.

Professor of chemistry there, Dr. Kobayashi has spent the last 30 years studying the chemistry of prebiotics. He was trying to understand how galactic cosmic rays—particles from outside the solar system—could have affected Earth’s early atmosphere. “Most researchers ignore galactic cosmic rays because they require specialized equipment, such as particle accelerators,” said Kobayashi. “I’m lucky enough to have access to a few of these near our facilities.” Small changes to Kobayashi’s experimental setup could put Hayrapetian’s ideas to good use. Scale.

Hayrapetyan, Kobayashi and their collaborators created a mixture of gases that corresponds to Earth’s early atmosphere as we understand it today. They combined carbon dioxide, molecular nitrogen, water, and varying amounts of methane. (The proportion of methane in Earth’s initial atmosphere is unknown, but thought to be low.) They ignited gas mixtures with protons (simulating solar particles) or spark discharges (simulating lightning) and recreated the Miller-Urie experiment for comparison.

As long as the methane content exceeded 0.5%, the mixtures fired by protons (solar particles) produced significant amounts of amino acids and carboxylic acids. But spark discharges (lightning) required a methane concentration of about 15% before any amino acids were formed.

Hayrapetyan added, “Even with 15 percent methane, the rate at which lightning produces amino acids is one million times lower than that produced by protons.” Protons also tend to produce more carboxylic acids (precursors of amino acids) than those ignited by spark discharges.

A close-up view of a solar flare, including a solar flare, coronal mass ejection, and solar particle event.Credit: NASA Goddard Space Flight Center All other things being equal, solar particles are a more efficient source of energy than lightning. However, Hayrapetyan suggested that most likely everything else was disorderly. Miller and Ury suggested that in the “warm little pond” days, lightning was as common as it is today. But lightning from storm clouds from rising hot air will be 30% rarer than from the dim Sun.

Hayrapetyan said, “Lightning never occurs in cold conditions, and the Earth’s early days were under a rather weak Sun.” Said. “This doesn’t mean it can’t come from lightning, but lightning now seems less likely and solar particles more likely.”

These experiments show that our active young Sun may have catalyzed the ancestors of life more easily, and perhaps sooner than previously thought.