  Ultraviolet (UV) radiation is common to most planetary environments, and
could play a key role in the chemistry of molecules relevant to abiogenesis
(prebiotic chemistry). In this work, we explore the impact of UV light on
prebiotic chemistry that might occur in liquid water on the surface of a planet
with an atmosphere. We consider effects including atmospheric absorption,
attenuation by water, and stellar variability to constrain the UV input as a
function of wavelength. We conclude that the UV environment would be
characterized by broadband input, and wavelengths below 204 nm and 168 nm would
be shielded out by atmospheric CO2 and water, respectively. We compare this
broadband prebiotic UV input to the narrowband UV sources (e.g. mercury lamps)
often used in laboratory studies of prebiotic chemistry, and explore the
implications for the conclusions drawn from these experiments. We consider as
case studies the ribonucleotide synthesis pathway of Powner et al (2009) and
the sugar synthesis pathway of Ritson et al (2012). Irradiation by narrowband
UV light from a mercury lamp formed an integral component of these studies: we
quantitatively explore the impact of more realistic UV input on the conclusions
that can be drawn from these experiments. Finally, we explore the constraints
solar UV input places on the buildup of prebiotically important feedstock
gasses like CH4 and HCN. Our results demonstrate the importance of
characterizing the wavelength dependence (action spectra) of prebiotic
synthesis pathways to determine how pathways derived under laboratory
irradiation conditions will function under planetary prebiotic conditions.
  Keywords: Laboratory Investigations; Origin of Life; Planetary Environments;
UV Radiation; RNA World
