Astrobiology: Creation of the Amino Acids

A puzzle that has baffled astrobiologists for decades is how all the amino acids, from which our bodies make proteins, ended up with a strong preference for left-handed chirality. In nature, molecules that possess chirality can be either “left-handed (LH)” or “right-handed (RH).” If one produces amino acids in the laboratory, as was done by Miller and Urey in the 1950s, one tends to produce equal numbers of LH and RH molecules, but somehow nature managed to favor LH amino acids to the virtual exclusion of their RH cousins.

Several theories exist to describe how the LH amino acids were created and selected, but observation of LH amino acids in meteorites suggests that amino acids are made in outer space. And their chirality is also apparently selected there.

The figure on the right shows the directions of the magnetic fields (B), the nuclear spins (SN), and the neutrino spin (Sν) in the vicinity of a forming neutron star following a supernova. This site is thought to be capable of producing some chirality in potentially chiral molecules.

Boyd’s Amino Acid Collaborations

astro-biology

Image credit: NASA

Boyd and his collaborators have developed one of the amino acid creation theories. It depends on processing the previously formed amino acids by the neutrinos emitted by a nascent neutron star created by a supernova. Also required is the molecular orientation that occurs in the ultra-strong magnetic field of the star. Work continues on this model.

See “Stardust, Supernovae, and the Molecules of Life: Might We All Be Aliens?” by Richard N. Boyd, Springer (2012).