35.03

Venus' surface temperature controlled by a coupled mechanism of chemical and albedo feedback

G. L. Hashimoto, Y. Abe (University of Tokyo)

The abundance of Venus' CO tex2html_wrap_inline11 atmosphere was suggested to be controlled or buffered by carbonation reaction on the surface (carbonate buffer), since the Venus' surface condition is so close to the equilibria over the calcite-quartz-wollastonite assemblage (CO tex2html_wrap_inline11 (gas) + CaSiO tex2html_wrap_inline15 = SiO tex2html_wrap_inline11 + CaCO tex2html_wrap_inline15 ). However, Bullock and Grinspoon [1996] and Hashimoto et al. [1997] pointed out that the atmosphere buffered by a carbonation reaction is not stable. Then, which mechanism control the Venus' atmosphere? Here we propose an alternative idea of regulating Venus' climate. Our new mechanism regulates the surface temperature to the present value for a given amount of CO tex2html_wrap_inline11 in the atmosphere. This mechanism may be considered just opposite to the carbonate buffer, which tries to regulate the surface pressure for a given surface temperature. We construct a coupled model of the cloud albedo and the chemical interaction between the atmosphere and surface rocks. Our model shows that the coupled effect of chemical reaction and albedo buffers the surface temperature change against variation in the solar constant and atmospheric CO tex2html_wrap_inline11 abundance. Our model shows that Venus' surface temperature is kept to be about 735 K throughout the Venus' history.