In 2021, the Hayabusa2 space mission successfully delivered a morsel of the asteroid 162173 Ryugu to Earth — five grams of the oldest, most pristine matter left over from the solar system’s formation 4.5 billion years ago. Last spring, scientists revealed that the chemical composition of the asteroid includes 10 amino acids, the building blocks of proteins. The discovery added to the evidence that the primordial soup from which life on Earth arose may have been seasoned with amino acids from pieces of asteroids.
But where did these amino acids come from? The amino acids flowing through our ecosystems are products of cellular metabolism, mostly in plants. What nonbiological mechanism could have put them in meteorites and asteroids?
Scientists have thought of several ways, and recent work by researchers in Japan points to a significant new one: a mechanism that uses gamma rays to forge amino acids. Their discovery makes it seem even more likely that meteorites could have contributed to the origin of life on Earth.
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