  Many of the building blocks of life such as amino acids and nucleotides are
chiral, i.e., different from their mirror image. Contemporary life selects and
synthesizes only one of two possible handednesses. In an abiotic environment,
however, there are usually equally many left- and right-handed molecules. If
homochirality was a prerequisite of life, there must have been physical or
chemical circumstances that led to the selection of a certain preference.
Conversely, if it was a consequence of life, we must identify possible pathways
for accomplishing a transition from a racemic to a homochiral chemistry. After
a discussion of the observational evidence, I will review ideas where
homochirality of any handedness could emerge as a consequence of the first
polymerization events of nucleotides in an emerging RNA world. These mechanisms
are not limited to nucleotides, but can also occur for peptides, as a precursor
to the RNA world. The question of homochirality is, in this sense, intimately
tied to the origin of life. Future Mars missions may be able to detect
biomolecules of extant or extinct life. We will therefore also discuss possible
experimental setups for determining the chirality of primitive life forms in
situ on Mars.
