Monday,
August 28, 2000
at 14:00
Martin Burgdorf
Space Science Department of ESA, ISO Data Center, Madrid
ISO Observations of Mars
Abstract.
Infrared spectra of Mars were taken in July and August 1997 with
the LWS (Long Wavelength Spectrometer) and the SWS (Short
Wavelength Spectrometer) onboard the European Space Agency's
Infrared Space Observatory, ISO. They covered the wavelength
range from 2.3 to 45 micron with a spectral resolution of about
1500 and from 45 to 180 micron with a resolution between 150 and
300. In addition, scans of selected H2O lines have been
recorded in Fabry-Perot mode, where the spectral resolution is
more than an order of magnitude higher.
A multitude of water lines was detected, and their strengths were
determined by means of Interactive Analysis tools. Comparisons of
the measured lines in the near-infrared with various synthetic
spectra allowed us to obtain information about the vertical
distribution of water vapor. Assuming atmospheric and surface
temperatures derived from the European Martian Climate Database
with a slight adjustment to the observed 15 micron CO2 band,
the ISO data indicate an H2O water distribution confined in
the lower atmosphere, within the first 11-15 km above the
surface, and a total column density of 12 ppt-micron.
Once the water vertical distribution was determined, the mean
surface emissivity remained as the most important unknown in the
model spectra for the far infrared and could therefore be derived
from the measured line to continuum ratios in the LWS range. It
was found to have an average value of 0.95 +- 0.03 and to be
slightly decreasing between 50 and 180 micron.
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