Cover Page/Proposal Summary

ROSS-00    NRA 00-OSS-01

Date Due: 4/28/2000

We propose a theoretical investigation of the recent evolution of climate on Venus. The geological history of Venus, as revealed by Magellan, is now detailed enough to provide significant constraints on the history of its climate. We will use Venus' geological record to test and refine models of the evolution of its atmosphere and clouds. Our climate models incorporate feedbacks between temperature dependent surface/atmosphere reactions and the radiative effects of clouds and greenhouse gases, which evolve in response to volcanic sources of volatiles. This project consists of the following tasks: We will (1) incorporate a detailed microphysical cloud model of Venus into the climate models, (2) use improvements in H2SO4/H2O optical constants, near-UV absorber treatment and estimates of geological sources of volatiles, (3) develop models of the coupling between surface temperature, mantle convection and partial melt efficiency, (4) study the role that impacts may have had in recent (1 Gy) changes in the clouds and atmosphere, and (5) provide an improved understanding of the history of water on Venus using constraints from cometary D/H and improved exospheric escape modeling. The surface of Venus records a series of volcanic and tectonic events that have both altered Venus' atmosphere and clouds and provided a signature of climate change. The globally synchronous formation of wrinkle ridges on the most widespread volcanic plains unit, emplaced in less than 100 My, were most likely due to the propagation of a climate-induced thermal wave that deformed the surface. In contrast, smaller, more recent volcanic events were insufficient to alter temperatures enough to cause surface deformation. Using the improvements to our climate models from tasks 1-5 above, we will produce models of the last 1 Gy of Venus atmosphere and cloud evolution that are consistent with the detailed global stratigraphy and volcanic history that are now becoming available.

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By submitting the proposal identified in this Cover Sheet/Proposal Summary in response to this NRA or AO, the Authorizing Official of the proposing institution (or the individual proposer if there is no proposing institution) as identified below: