Response of dust on thermal emission spectra observed by Planetary Fourier3 Spectrometer (PFS) on-board Mars Express (MEX)

The thermal emission spectra have provided many useful insights about the Martian atmosphere and surface. The interpretation of the thermal emission spectra can give us information about atmospheric temperature, pressure, mineralogy and presence of atmospheric constituents including their isotopes. In the present work, we have analysed the thermal emission data for dust storm season on Mars. The signature of dust in the thermal emission spectra for Martian Year (MY) 28 confirms presence (Ls=280o and 300o) and absence (Ls=240o and 320o) of the dust storm at latitude range 0o-10oS, 10o-20oS and 20o-30oS. We have compared our results with earlier mission data with thermal emission measurements made by Planetary Fourier Spectrometer (PFS) on-board Mars Express (MEX) between wave numbers 250-1400 cm-1. We have observed features at wave numbers 600-750 cm-1 and 900-1200 cm-1 due to absorptions by CO2 and dust respectively. We have obtained brightness temperatures from thermal emission spectra by inverting the Planck function. The maximum brightness temperature ~280 K is measured at Ls=240o when Mars received a large amount of solar radiation at perihelion. The minimum brightness temperature ~ 220o K is observed at Ls=320o in the absence of dust storm. In presence of dust storm thermal emission spectra and brightness  temperatures are reduced by factors of ~ 3.0 and ~1.3 respectively between wave numbers 900-1200 cm-1 in comparison to that observed in absence of dust storm

Modeling infrared thermal emissions on Mars during dust storm of MY28: PFS/MEX observation

We have analysed thermal emission spectra obtained from Planetary Fourier Spectrometer (PFS) onboard Mars Express (MEX) for Martian Year (MY) 28 in presence and absence of dust storm at low latitude. A radiative transfer model for dusty atmosphere of Mars is developed to estimate the thermal emission spectra at latitude range 0-10oS, 10-20oS and 20-30oS. These calculations are made at Ls=240o, 280o, 300o, and 320o between wave numbers 250-1400 cm-1. We have also retrieved brightness temperatures from thermal emission spectra by inverting the Planck function. The model reproduces the observed features at wave numbers 600-750 cm-1 and 900-1200 cm-1 due to absorptions by CO2 and dust respectively. In presence of dust storm thermal emission spectra and brightness temperature are reduced by a factor of ~ 2 between wave numbers 900-1200 cm-1. The altitude profiles of dust concentration are also estimated for different aerosol particles of sizes 0.2 to 3 micron. The best fit to the PFS measurements is obtained in presence of aerosol particle of size 0.2 micron