The weak nuclear interaction is a universal force. If parity non-conserving energy differences based on the weak nuclear interaction were involved in life's choice for the homochiral structure of its biopolymers, then life based on the same chemical elements as ours (amino acids, ribose, etc.) anywhere in the Universe would contain molecules of the same chirality as observed on Earth. If so, then "left-life" might extend throughout the universe. "Right-life" would be possible only in an antimatter world where the weak force could go the other way (Gardner 2005).
With all other sources of homochirality such as magnetochiral anisotropies or circularly polarized electromagnetic radiation, the sign of the handedness will be accidental. The same or the opposite chirality as on Earth would be equally possible on life-supporting planets in other Solar Systems (Borchers et al. 2004).
If, for example, astronauts find right-handed amino acids on Mars, it could be excluded that asymmetry on the particle level could be a factor in determining the handedness of organic molecules. Accordingly, in the upcoming chapters we will focus on the determination of enantiomeric enhancements in extraterrestrial samples. Particularly, meteorites were subjected to enantioselective analyses of their chiral organic ingredients including amino acids (see Chap. 8), but also simulated cometary matter was shown to contain a wide variety of amino acids (see Chap. 7). Authentic cometary matter will be analyzed enantioselectively in the near future after landing on a comet; the same is true for the enantiomer-separating analysis of Martian organic molecules (see Chap. 9).
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