Enormous superflares from young Sun may have sparked life on Earth, new study suggests

A groundbreaking study proposes that life on Earth might have been initiated by massive superflares emitted by a hyperactive young sun. Scientists have discovered that by directing charged particles from the solar wind towards a combination of gases present in Earth's early atmosphere, significant quantities of amino acids and carboxylic acids—the essential building blocks of proteins and all organic life—can be formed.

Since the 1800s, researchers have been grappling with the enigma of how life originated on our planet. One hypothesis suggests that life may have emerged in a primordial chemical soup known as a "warm little pond." In the 1950s, experiments involving gas mixtures of methane, ammonia, water, and molecular hydrogen exposed to artificial lightning provided some insights.

However, over the years, the situation has grown more complex. Scientists have discovered that Earth's early atmosphere contained less ammonia and methane than previously believed, while carbon dioxide and molecular nitrogen were more prevalent. Both gases require significantly more energy to break down compared to what lightning alone can provide.

Recently, a study published in the journal Life on April 28 has shed new light on this puzzle. Using a particle accelerator, researchers found that cosmic rays from intensely energetic superflares could have supplied the necessary impetus for life to begin on Earth.

Lead study author Kensei Kobayashi, a chemistry professor at Yokohama National University in Japan, remarked, "Most investigators ignore galactic cosmic rays because they require specialized equipment, like particle accelerators. I was fortunate enough to have access to several of them near our facilities."

Stars generate powerful magnetic fields as a result of the flow of electrical charges in the molten plasma beneath their surfaces. Occasionally, these magnetic field lines form knots and abruptly snap, releasing bursts of radiation called solar flares and explosive jets of solar material known as coronal mass ejections (CMEs).

When this solar material, consisting primarily of electrons, protons, and alpha particles, collides with Earth's magnetic field, it triggers a geomagnetic storm. The agitation of molecules in our atmosphere during such events produces colorful auroras, like the northern lights. The largest solar storm on record, the 1859 Carrington Event, released an energy equivalent to approximately 10 billion 1-megaton atomic bombs. However, even this event pales in comparison to the power of a superflare, which can be hundreds to thousands of times more energetic.

Superflares of this magnitude typically occur once every century or so. However, recent research examining data from NASA's Kepler mission, which observed Earth-like planets and their stars from 2009 to 2018, revealed that during Earth's first 100 million years, the sun was 30% dimmer, yet superflares erupted from its surface every three to 10 days.

To understand the role of superflares in the production of amino acids on ancient Earth, the scientists behind the new study combined carbon dioxide, molecular nitrogen, water, and varying amounts of methane to simulate gas mixtures resembling our early atmosphere. By subjecting these mixtures to protons from a small particle accelerator or igniting them with simulated lightning, the researchers successfully triggered the synthesis of amino acids and carboxylic acids, crucial chemical components for life.

As the methane levels were increased, both the proton bombardment and the lightning discharges resulted in higher quantities of amino acids and carboxylic acids. However, the proton mixture required only a 0.5% methane concentration to produce detectable levels, while the lightning discharges necessitated a 15% concentration.

"And even at 15% methane, the production rate of the amino acids by lightning is a million times less than by protons," said study co-author Vladimir Airapetian, an astrophysicist at NASA’s Goddard Space Flight Center, who also worked on the 2016 Nature Geosciences study. "During cold conditions you never have lightning, and early Earth was under a pretty faint sun. That's not saying that it couldn't have come from lightning, but lightning seems less likely now, and solar particles seem more likely."