Collision-Induced Absorption of CH$_{4}$-CO$_{2}$ and
H$_{2}$-CO$_{2}$ Complexes and Their Effect on the Ancient
Martian Atmosphere
Abstract
Experimental measurements of collision-induced absorption (CIA)
cross-sections for CO2-H2 and CO2-CH4 complexes were performed using
Fourier transform spectroscopy over a spectral range of 100-500 cm and a
temperature range of 200-300 K. These experimentally derived CIA
cross-sections agree with the spectral range and temperature dependence
of the calculation by \citeA{Robin}, however the
amplitude is half of what was predicted. Furthermore, the CIA
cross-sections reported here agree with those measured by
\citeA{Turbet}. The CIA cross-sections can be applied
to planetary systems with CO$_{2}$-rich atmospheres, such as Mars
and Venus, and will be useful to terrestrial
spectroscopists.
Additionally, radiative transfer
calculations of the early Mars atmosphere were performed and showed that
CO2$-CH4 CIA would require surface pressure greater than 3 bar for a
10% methane atmosphere to achieve 273 K at the surface. CO2-H2,
however, liquid water is possible with 5% hydrogen and less than 2 bar
of surface pressure.