| | 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. |
