Ozone abundance on Mars from infrared heterodyne spectra II.: Validating photochemical models

Ozone is an important observable tracer of martian photochemistry. including odd hydrogen (HOx) species important to the chemistry and stability of the martian atmosphere. Infrared heterodyne spectroscopy with spectral resolution >= 10(6) provides the only ground-based direct access to ozone absorption features in the martian atmosphere. Ozone abundances were measured with the Goddard Infrared Heterodyne Spectrometer and the Heterodyne Instrument for Planetary Wind and Composition at the NASA Infrared Telescope Facility on Mauna Kea, Hawai'i. Retrieved total ozone column abundances from various latitudes and orbital positions (L-S = 40 degrees, 74 degrees, 102 degrees, 115 degrees, 202 degrees, 208 degrees, 291 degrees) are compared to those predicted by the first three-dimensional gas phase photochemical model of the martian atmosphere [Lefevre. F., Lebonnois, S., Montmessin, F., Forget, F., 2004. J. Geophys. Res. 109, doi: 10.1029/2004JE002268. E07004]. Observed and modeled ozone abundances show good agreement at all latitudes at perihelion orbital positions (LS = 202 degrees, 208 degrees, 291 degrees). Observed low-latitude ozone abundances are significantly higher than those predicted by the model at aphelion orbital positions (L-S = 40 degrees, 74 degrees, 115 degrees). Heterogeneous loss of odd hydrogen onto water ice cloud particles would explain the discrepancy, as clouds are observed at low latitudes around aphelion on Mars. (c) 2006 Elsevier Inc. All rights reserved.