This chapter reviews the first year of results from the Planetary Fourier Spectrometer (PFS) of Mars Express. An average global spectrum ranging from 200 cm-1 to 8200 cm-1 is compared with the martian spectrum from the Short Wavelength Spectrometer of the Infrared Space Observatory (ISO), and with the global synthetic spectrum computed using only the gases CO 2, CO and H2O. PFS is able to measure the vertical temperature-pressure profile in the atmosphere and the temperature of the soil simultaneously with the dust and water-ice opacity. The short-wavelength channel shows the major CO2 bands at 4.3 μm and 2.7 μm. The bottom of the first band shows very clearly the non-local thermodynamic equilibrium emission of the high atmospheric CO2 gas, while the limb measurements show CO emission. All the isotopic CO2 molecules appear to be emitting at the same radiance level, implying strong energy pumping from the most abundant to the less abundant molecules. In one of the first passes over Olympus Mons, the temperature field shows abnormal adiabatic cooling in the atmosphere above the mountain, while the soil temperature of the volcano is higher than the latitudinal profile expectation because of illumination from the Sun. The descending branch of the Hadley cell circulation is studied in detail, with its adiabatic heating and formation of water-ice clouds. Of the many unidentified lines observed, a few have been studied and the presence of methane (10 ppbv), HF (200 ppbv) and HBr (150 ppbv) is reported here. PFS has allowed the study of the composition of the permanent south polar cap: an intimate mixture model of mostly CO2 ice, ppm of water ice and some dust fits the data very well. Almost pure water-ice and CO2-ice spectra have been observed in specific locations. Finally, many solar lines are being observed; a few are being studied and compared with ISO observations and the solar spectrum assembled for PFS. In certain spectral regions, Mars looks like a Lambertian screen, reflecting an almost unperturbed solar spectrum.
PFS: Planetary fourier spectrometer
Saggin B.;
2009
Abstract
This chapter reviews the first year of results from the Planetary Fourier Spectrometer (PFS) of Mars Express. An average global spectrum ranging from 200 cm-1 to 8200 cm-1 is compared with the martian spectrum from the Short Wavelength Spectrometer of the Infrared Space Observatory (ISO), and with the global synthetic spectrum computed using only the gases CO 2, CO and H2O. PFS is able to measure the vertical temperature-pressure profile in the atmosphere and the temperature of the soil simultaneously with the dust and water-ice opacity. The short-wavelength channel shows the major CO2 bands at 4.3 μm and 2.7 μm. The bottom of the first band shows very clearly the non-local thermodynamic equilibrium emission of the high atmospheric CO2 gas, while the limb measurements show CO emission. All the isotopic CO2 molecules appear to be emitting at the same radiance level, implying strong energy pumping from the most abundant to the less abundant molecules. In one of the first passes over Olympus Mons, the temperature field shows abnormal adiabatic cooling in the atmosphere above the mountain, while the soil temperature of the volcano is higher than the latitudinal profile expectation because of illumination from the Sun. The descending branch of the Hadley cell circulation is studied in detail, with its adiabatic heating and formation of water-ice clouds. Of the many unidentified lines observed, a few have been studied and the presence of methane (10 ppbv), HF (200 ppbv) and HBr (150 ppbv) is reported here. PFS has allowed the study of the composition of the permanent south polar cap: an intimate mixture model of mostly CO2 ice, ppm of water ice and some dust fits the data very well. Almost pure water-ice and CO2-ice spectra have been observed in specific locations. Finally, many solar lines are being observed; a few are being studied and compared with ISO observations and the solar spectrum assembled for PFS. In certain spectral regions, Mars looks like a Lambertian screen, reflecting an almost unperturbed solar spectrum.
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