Despite Venus and Earth having distinct
atmospheres and surface temperatures,
they have similar densities and sizes. They may also have
similar bulk
compositions, making comparison between them extremely
valuable for
illuminating their distinct climate histories and their
exoplanetary cousins.
We use presently available data on Venus alongside knowledge
about Earth's
climate history to support a number of different evolutionary
hypotheses.
Evaluating several snapshots in time over the past 4+ billion
years, we show
that Venus may have sustained liquid water and moderate
temperatures for much
of this period. Cloud feedbacks from a slowly rotating world
with surface
liquid water reservoirs are keys to keeping the planet
clement. Yet how could
Venus go from habitable to hot-house? Our results demonstrate
that it was not
the gradual warming of the sun over the eons that contributed
to Venus' present
hot-house state. Rather we hypothesize that large scale
volcanism and the
observed global resurfacing could have played key roles in
ending the clement
period in its history and aligning our models with Venus'
present day atmosphere.
I will also touch on connections to upcoming Venus missions
and exoplanetary
observations that can test our hypotheses.
About the Speaker:
Mike is a physical scientist at The NASA
Goddard Institute for Space Studies in New York City, and
previously a visiting professor in the Department of Physics
and Astronomy at Uppsala University in Sweden, and the
Theoretical Astrophysics Center in Copenhagen, Denmark. He was
awarded his Physics PhD in Observational Cosmology in 1998
from the University of Missouri. He has used Machine Learning
to characterize the large scale structure of the universe,
worked in the history of Astronomy, and in recent years the
modeling of planetary atmospheres using a three-dimensional
general circulation model known as ROCKE-3D. His most recently
published work attempts to reconstruct Venus' climate history
over its 4.5 billion year lifespan.