ature Fragments collected from the asteroid Bennu contain the building blocks for life — all five nucleobases that form DNA and RNA and 14 of the 20 amino acids needed to make known proteins. But there’s a twist: on Earth, amino acids in living organisms tend to have a ‘left-handed’ structure. Those on Bennu, however, contain nearly equal amounts of these structures and their ‘right-handed’, mirror-image forms. This calls into question a hypothesis favoured by many scientists that asteroids similar to this one might have seeded life on Earth.
“I know which is my left hand because I write with it!”
Saying “I know which is my left...
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