  CO2 ice is present on the trailing hemisphere of Ariel but is mostly absent
from its leading hemisphere. The leading/trailing hemispherical asymmetry in
the distribution of CO2 ice is consistent with radiolytic production of CO2,
formed by charged particle bombardment of H2O ice and carbonaceous material in
Ariel's regolith. This longitudinal distribution of CO2 on Ariel was previously
characterized using 13 near-infrared reflectance spectra collected at 'low'
sub-observer latitudes between 30S to 30N. Here, we investigated the
distribution of CO2 ice on Ariel using 18 new spectra: two collected over low
sub-observer latitudes, five collected at 'mid' sub-observer latitudes (31 -
44N), and eleven collected over 'high' sub-observer latitudes (45 - 51N).
Analysis of these data indicates that CO2 ice is primarily concentrated on
Ariel's trailing hemisphere. However, CO2 ice band strengths are diminished in
the spectra collected over mid and high sub-observer latitudes. This
sub-observer latitudinal trend may result from radiolytic production of CO2
molecules at high latitudes and subsequent migration of this constituent to low
latitude cold traps. We detected a subtle feature near 2.13 microns in two
spectra collected over high sub-observer latitudes, which might result from a
'forbidden' transition mode of CO2 ice that is substantially stronger in well
mixed substrates composed of CO2 and H2O ice, consistent with regolith-mixed
CO2 ice grains formed by radiolysis. Additionally, we detected a 2.35-micron
feature in some low sub-observer latitude spectra, which might result from CO
formed as part of a CO2 radiolytic production cycle.
