Analyses of samples harvested from a near-Earth asteroid suggest it broke billions of years ago from a much larger, watery object containing crucial ingredients to life, according to research released yesterday.
In 2020, NASA's OSIRIS-REx mission collected a quarter-pound sample of regolith, or dirt, from the one-third-mile-wide asteroid Bennu, returning it to Earth in Utah in 2023. Early analyses identified 14 of 20 amino acids crucial to life on Earth in the sample, as well as all five nucleobases comprising genetic code. Additionally, a type of salt was discovered, suggesting the asteroid may have once been covered in salty ponds where amino acids had the potential to mix with other minerals and form organic compounds.
In a surprise to researchers, the asteroid's amino acids are made of an equal proportion of the molecule and its mirror-image structure, similar to right- and left-handedness. Earth's amino acids consist mostly of just one side of that mirror image, known as left-handed chirality, casting doubt on a long-held theory that life's ingredients arrived on Earth via such asteroids (see explainer).
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