A long-standing mystery about the origin of life has a new possible solution.
The puzzle is that amino acids, the constituents of proteins, occur in two chemically identical forms that have structures mirroring each other like two gloves. Most chemical processes yield left- and right-handed amino acids in equal amounts yet life forms contain left-handed amino acids almost exclusively. New findings show that a mineral common on the ancient Earth might have segregated the mirror-image versions.
Much speculation has focused on extraterrestrial influences behind early life. Some scientists suggest that extra left-handed amino acids arrived on meteorites as life was emerging on Earth (SN: 2/22/97, p. 118). In another theory, Earth formed from dust harboring a primordial excess of left-handed amino acids.