  Conceptualizing planetary habitability depends on understanding how living
organisms originated and what features of environments are essential to foster
abiogenesis. Estimates of the abundance of life's building blocks are
confounded by incomplete knowledge of the role of chirality and racemization in
organic compounds in the origination of living organisms. Chirality is an
essential feature of enzymes as well as many lock-and-key type structures.
There are four known processes that can act on complex organic molecules to
promote racemization for abiogenesis: quantum-tunneling effects; selection via
interaction with circularly polarized light (CPL); templating processes; and
interactions with electrical and magnetic (EM) fields. These occur in different
places, respectively: cold interstellar space; regions of space with energetic
photons, dust and/or magnetic fields; and mineral surfaces (for both templating
and EM fields). Chirality as a feature of terrestrial life suggests neither a
special place for local development of homochirality nor for extra-terrestrial
enrichment and delivery. The presence of these molecules in three competing
scenarios for life's origin - chemical gardens, geothermal fields, and ice
substrates - relies on a framework of hypothesis and estimation. An
easily-modified worksheet is included in the supplemental material that allows
a user to generate different scenarios and data related to the distribution of
chiral organic molecules as building blocks for living organisms within the
galaxy. A simple hypothetical mechanism for planetary magnetic field reversals,
based on a high-density plasma inner core, is also presented as a means to aid
in estimating field polarity and hence the orientation of racemization
processes based on planetary magnetic fields.
