Research suggests that the very first building blocks of life on our planet may have been formed with help from eruptions from our Sun. The findings, based on a series of chemical experiments, demonstrate how solar particles colliding with gases in Earth's early atmosphere could generate amino acids and carboxylic acids - the fundamental building blocks of proteins and organic life. These exciting revelations were recently published in the scientific journal Life.
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The origin of life is a topic that has intrigued and perplexed scientists for centuries. A particularly vexing question is how amino acids, which form the base of proteins and all cellular life, came to be.
Since the late 1800s, the most popular hypothesis has been that life began in a "warm little pond" where a mix of chemicals, energized by various sources like lightning and heat, could combine to form organic molecules.
This proposal was given credence in 1953 when Stanley Miller, a University of Chicago scientist, replicated these primordial conditions in the lab. He filled a chamber with gases prevalent in Earth's early atmosphere, including methane, ammonia, water, and molecular hydrogen, and introduced an electrical spark simulating lightning. Upon analysis a week later, 20 different amino acids were found to have formed.
Vladimir Airapetian, a stellar astrophysicist at NASA's Goddard Space Flight Center and coauthor of the new study, explained that these complex organic molecules can be synthesized from the basic components of early Earth's atmosphere.
However, over the last 70 years this picture has become more complicated. Recent research suggests that methane and ammonia were not as abundant as initially believed, replaced instead by carbon dioxide and molecular nitrogen. Although these gases can produce amino acids, the quantity is significantly reduced.
In the quest to identify alternative energy sources, scientists have considered shockwaves from meteor impacts and solar ultraviolet radiation. However, Airapetian has proposed a new hypothesis: energetic particles from our Sun.
Using data from NASA's Kepler mission, which observed stars at various stages of their lifecycle, Airapetian suggested that our Sun was about 30% dimmer during Earth's first 100 million years. Despite this, it would have frequently erupted with powerful "superflares" that launched near-light speed particles colliding with our atmosphere, triggering chemical reactions.
This led to collaboration with Dr. Kobayashi, a professor of chemistry at Yokohama National University in Japan, who had been studying how cosmic rays could have influenced early Earth's atmosphere. They decided to replicate Earth's early atmosphere and expose it to both solar particles and electrical sparks, simulating both solar activity and lightning, respectively.
Artist impression of early Earth - (Credit: NASA)
The results were fascinating. When methane concentration was above 0.5%, the gas mixtures exposed to protons (solar particles) yielded detectable amounts of amino acids and carboxylic acids.
In contrast, a methane concentration of around 15% was required for spark discharges (lightning) to produce any amino acids. Furthermore, the production rate of amino acids via solar particles was a million times higher than that via lightning.
Solar particles are a more efficient energy source for generating amino acids than lightning. Airapetian suggests that lightning, a result of thunderclouds formed by rising warm air, would have been less common under a 30% dimmer Sun.
These experiments seem to indicate that our active young Sun may have been a catalyst in the formation of life's precursors more readily and perhaps earlier than previously assumed.
If you are interested in reading more about the subject, check out the paper published in the peer-reviewed science journal Life, listed below.
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