10:10 AM - 10:25 AM
[MIS07-10] Effects of the formation of hydrocarbon aerosols on the climate stability of Earth-like planets and their habitability
Keywords:Habitability, Climate stability
Here we developed a coupled atmospheric photochemistry-marine microbial ecosystem-global carbon cycle model to explore how the atmospheric photochemistry and the primitive marine microbial ecosystem can affect the carbon cycle and CO2 budget on the Earth-like planet. We found that when the primitive biosphere produces large CH4 flux (~1011 cm-2 s-1), OH radicals should be consumed in the lower atmosphere through the reaction with CH4. As a result, the reaction between CO and OH, which produces CO2, cannot compensate the photolysis of CO2 in the upper atmosphere. This means that photochemical reactions may work as a net CO2 consumption process in the atmosphere-ocean system. The excess CO in the atmosphere is considered to have been converted to CO2 and CH4 through the CO-using chemosynthesis and methanogenesis in the oceans on the early Earth. Therefore, marine microbial reactions can work as a net CO2 production process in the atmosphere-ocean system. We also found that, when the CO2 level is so low that the hydrocarbon haze can form, the photochemical net consumption of CO2 exceeds the biospheric net production. In this case, CO2 is removed from the atmosphere-ocean system as the haze particle. As a result, the climate with the hydrocarbon haze should be unstable, and the climate is expected to change to the snowball state with low pCO2 or to the hot climate state (> ~310 K on the CO2 degassing rate of the present Earth) with high pCO2 and pCH4 on the planets with anoxic environment and primitive microbial ecosystem in the ocean.
Our result would put a theoretical constraint on the existence of life on extrasolar Earth-like planets and their habitability.