Fragments of the asteroid Bennu, carefully collected and ferried to Earth by a robotic spacecraft, contain the building blocks for life, NASA announced today.
Not only does Bennu contain all 5 of the nucleobases that form DNA and RNA on Earth and 14 of the 20 amino acids found in known proteins, the asteroid’s amino acids hold a surprise. On Earth, amino acids in living organisms predominantly have a ‘left-handed’ chemical structure. Bennu, however, contains nearly equal amounts of these structures and their ‘right-handed’, mirror-image forms, calling into question scientists’ hypothesis that asteroids similar to this one might have seeded life on Earth.
The work appears in Nature Astronomy1.
“What makes these results so significant is that we’re finding them in a pristine sample,” says co-author Daniel Glavin, an astrobiologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. When meteorites fall to Earth, they are heated in the atmosphere and contaminated by the planet’s molecules. The Bennu samples were ferried to Earth in a sealed canister, protected from the heat, and analysed in a super-clean laboratory space under inert gas.
The specimens contain the richest bounty of life-friendly extraterrestrial compounds ever brought to Earth.
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