Astronomy and Astrophysics – Astronomy
Scientific paper
May 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003dps....35.0304l&link_type=abstract
American Astronomical Society, DPS meeting #35, #03.04; Bulletin of the American Astronomical Society, Vol. 35, p.913
Astronomy and Astrophysics
Astronomy
Scientific paper
On June 6--15, 2003, we observed the narrow 10.6 μ m infrared emission feature ( ˜ 0.0016 cm-1) of normal-isotope carbon dioxide originating in the mesosphere of Mars, superposed on the relatively broad ( ˜ 0.02 cm-1) absorption feature of tropospheric CO2. Spectra of the emission core were acquired at a spectral resolving power of λ / Δ λ = 5x 106 using the Heterodyne Instrument for Planetary Winds and Composition (HIPWAC) at the NASA Infrared Telescope Facility. Lower-resolution spectra (λ / Δ λ = 1x 106) acquired simultaneously characterize the wings of the ``broad'' absorption feature. Thermal profile information to an altitude of ˜40 km is recorded in the shape of the tropospheric line; mesospheric temperatures at ˜60--80 km are recorded by the Doppler width of the emission feature. These data thus provide a measure of Mars' thermal profile over a broad range of altitude, complementing results from the Mars Global Surveyor (MGS) TES instrument for the troposphere and providing the only remote method to experimentally determine temperatures in the mesosphere. Spectra of a single CO2 line were obtained from 9 positions spaced 15o in latitude along the 2PM meridian ground track of the MGS spacecraft between 45oN latitude and 75oS latitude, providing temperatures at each location. Spectra were acquired at the equator at six other CO2 lasing transitions in order to constrain the rotational temperature for comparison to the kinetic temperature derived from the Doppler width of the emission core. In addition to the expected strong normal-isotope lasing transitions appearing in Mars' atmosphere, two additional classes of features were detected at high signal-to-noise ratio: relatively weak secondary lines of CO2 were observed near several lasing transitions, and features of 16O12C18O (628 carbon dioxide) were detected with high statistical significance.
This work is supported by the NASA Planetary Astronomy Program.
Annen J. N.
Fast Kelly Elizabeth
Hewagama Tilak
Kostiuk Theodor,
Livengood Timothy A.
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