Collision-Induced Absorption of CH4-CO2 and H2-CO2 Complexes and Their
Effect on the Ancient Martian Atmosphere
Abstract
Experimental measurements of collision-induced absorption (CIA)
cross-sections for CO-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 Wordsworth (2017), however the amplitude is half
of what was predicted. Furthermore, the CIA cross-sections reported here
agree with those measured by Turbet (2019). The CIA cross-sections can
be applied to planetary systems with CO2-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.