The Climate on Venus

Fred TaylorVenus Express Interdisciplinary ScientistEGU Vienna 16 April 2008

Venus and Earth

• Trace origins & evolution

• Understand common processes

• Model current climate(s)

PAST

Atmosphere

Space

Surface

Interior

Climate

Atmosphere

Space

Surface

Interior

FUTURE

Atmosphere

Space

Surface

Interior

RadiationDynamics

ChemistryChemistry

PAST

Atmosphere

Space

Surface

Interior

Climate

Atmosphere

Space

Surface

Interior

Future

Atmosphere

Space

Surface

Interior

Volcanism ?

Volcanism on Venus- Key Questions

• Is volcanic activity present now?• Quantify vocanic input to the

atmosphere, past, present & future?• Role in current climate(s)?• Likely past/future evolution?

First observations of SO2 above Venus’ cloudsby means of solar occultation in the infrared

D. Belyaev, O. Korablev, A. Fedorova, J.-L. Bertaux,A.-C. Vandaele, R. Drummond, A. Mahieux, V. Wilquet

Sulphur compounds in Earth’s atmosphere (Whitten, Toon, & Turco, 1979)

21 Sept 1991, 100 days after the eruption injected ~20 million tons of SO2 into stratosphere. Lifetime ~ 100 days

← Venera 9 obtained the first image from the surface of Venus in 1975.

↓ View of a plain in Phoebe Regio from Venera 13 on March 1, 1982

Maat Mons from Magellan Radar Image

Venus has more volcanoes than any other planet in the solar system. Over 1600 major volcanoes or volcanic features are known (see map), and there are many, many more smaller volcanoes. No one has yet counted them all, but the total number may be over 100,000 or even over 1,000,000. [Oregon State University]

Venus Express extended mission until end of June 2009Japanese Venus Climate Orbiter arrives December 2010

The EndE. Marcq et al. (VIRTIS)

Total sulphur (as gas) in atmosphere of Venus ≈ 10,000,000 times Earth

The Surface of Venus from Orbit by VEx and Magellan

J Helbert et al.

Volcanism on Venus- Evidence

• Surface panoramas & global radar images– reveal thousands of volcanic features

• Sulphur content of atmosphere– Stratospheric SO2 >> (~105x) Earth

– H2SO4 clouds

– Deep atmosphere SO2 ~ 130 ppm(~105x) Earth

– CO2 at equilibrium with surface, SO2 out by > 100

• Earth is volcanic

Volcanism on Venus- Caveats

1. Rainout on Earth removes SO2 quickly, c.f. 1-10 Myr for SO2 removal on Venus

2. If global resurfacing ended 500 Myr ago, atmospheric sulphur may be of ancient origin

3. Could hot dry Venus surface be a source?

Volcanism on Venus- What can VEx do?

• Study SOStudy SO22 variability in upper atmosphere variability in upper atmosphere

• Study SOStudy SO22 variability in lower atmosphere variability in lower atmosphere

• Find thermal anomalies on the surfaceFind thermal anomalies on the surface• New theoretical studiesNew theoretical studies

– Models of interior, surface, clouds &cModels of interior, surface, clouds &c– Earth analoguesEarth analogues

• Sponsor new missionsSponsor new missions

Conclusion: processes determine rates, it should be the reverse!

Why is it important?

• Gases & cloud opacity warm climate

• H2SO4 cloud albedo cools climate

• Both time-dependent; change if volcanic activity changes or stops

• CO2 and H2O are both volcanic gases and may also change

The Surface of Venus seen from Orbit

The ‘Greenhouse’ effect on Earth and Venus

QuickTime™ and a decompressor

are needed to see this picture.

Effect of changing composition on the surface temperature of Venus (Bullock 1997)

Cloud effect does not include albedo!

Venus

400 KSurface

Bullock & Grinspoon, JGR, 1996

To be continued........