  We have obtained the first continuous disk averaged spectrum of Mars from 450
to 1550 Ghz using the Herschel-SPIRE Fourier Transform Spectrometer. The
spectrum was obtained at a constant resolution of 1.4 GHz across the whole
band. The flux from the planet is such that the instrument was operated in
"bright source" mode to prevent saturation of the detectors. This was the first
successful use of this mode and in this work we describe the method used for
observing Mars together with a detailed discussion of the data reduction
techniques required to calibrate the spectrum. We discuss the calibration
accuracy obtained and describe the first comparison with surface and
atmospheric models. In addition to a direct photometric measurement of the
planet the spectrum contains the characteristic transitions of 12CO from J 5-4
to J 13-12 as well as numerous H2O transitions. Together these allow the
comparison to global atmospheric models allowing the mean mixing ratios of
water and 12CO to be investigated. We find that it is possible to match the
observed depth of the absorption features in the spectrum with a fixed water
mixing ratio of 1 x 10-4 and a 12CO mixing ratio of 9 x 10-4
