The Climate on Venus Fred Taylor Venus Express Interdisciplinary Scientist EGU 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 Radiation Dynamics Chemistry

PAST Atmosphere Space Surface Interior Climate Atmosphere Space Surface Interior Future Atmosphere Space Surface InteriorVolcanism ?

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 SO 2 above Venus’ clouds by 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 ↓ 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 2009 Japanese Venus Climate Orbiter arrives December 2010 The End E. 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 SO 2 >> (~10 5 x) Earth –H 2 SO 4 clouds –Deep atmosphere SO 2 ~ 130 ppm(~10 5 x) Earth –CO 2 at equilibrium with surface, SO 2 out by > 100 Earth is volcanic

Volcanism on Venus - Caveats 1.Rainout on Earth removes SO 2 quickly, c.f Myr for SO 2 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 SO 2 variability in upper atmosphereStudy SO 2 variability in upper atmosphere Study SO 2 variability in lower atmosphereStudy SO 2 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 &c –Earth analogues Sponsor new missionsSponsor new missions

Conclusion: processes determine rates, it should be the reverse! Why is it important? Gases & cloud opacity warm climate H 2 SO 4 cloud albedo cools climate Both time-dependent; change if volcanic activity changes or stops CO 2 and H 2 O are both volcanic gases and may also change

The Surface of Venus seen from Orbit The ‘Greenhouse’ effect on Earth and Venus

Effect of changing composition on the surface temperature of Venus (Bullock 1997) Cloud effect does not include albedo!

Venus 400 K Surface Bullock & Grinspoon, JGR, 1996

To be continued