1. PHOTON AND WATER MEDIATED SULFUR OXIDE AND ACID CHEMISTRY IN THE ATMOSPHERE OF VENUS Jay A. Kroll, Veronica Vaida Department of Chemistry and Biochemistry University of Colorado - Boulder June 20, 2014 Photo Credit: J. Gabás Esteban

2. Sulfur compounds have been observed on a number of planetary bodies. Photo credit: ESA VenusEarthMars IoEuropaCallisto

3. Sulfur compounds have been observed on a number of planetary bodies. Venus – Sulfuric acid clouds 50-70 km http://nssdc.gsfc.nasa.gov/image/planetary/venus/pvo_uv_790226.jpg

4. Belyaev et al. Icarus, Volume 217, Issue 2, 2012, 740 - 751 Mixing Ratio (ppm v ) Altitude (km) SO 2 SO Sulfur compounds have been observed on a number of planetary bodies. Venus – Sulfuric acid clouds 50-70 km – Increase in SO 2 at 90 km – Exceeds model predictions by orders of magnitude

5. Belyaev et al. Icarus, Volume 217, Issue 2, 2012, 740 - 751 Mixing Ratio (ppm v ) Altitude (km) SO 2 SO Sulfur compounds have been observed on a number of planetary bodies. Venus – Sulfuric acid clouds 50-70 km – Increase in SO 2 at 90 km – Exceeds model predictions by orders of magnitude – Requires a chemical source of SO 2 in the middle atmosphere

6. UV photolysis of H 2 SO 4 H 2 SO 4 + UV  SO 3 +H 2 O SO 3 + UV  SO 2 +O

7. UV photolysis of H 2 SO 4 H 2 SO 4 + UV  SO 3 +H 2 O SO 3 + UV  SO 2 +O Lane and Kjaergaard, J Phys. Chem A. 2008, 112, 4958-4964 180 nm Sulfuric Acid Cross Section

8. UV photolysis of H 2 SO 4 H 2 SO 4 + UV  SO 3 +H 2 O SO 3 + UV  SO 2 +O Lane and Kjaergaard, J Phys. Chem A. 2008, 112, 4958-4964 180 nm Sulfuric Acid Cross Section Spectral Actinic Flux of Venus Zhang et al. Icarus, Volume 217, Issue 2, 2012, 714 - 739 58 km 70 km 112 km

9. Sulfuric acid – Modeling – Photolysis – Earth explanation Modeling of Venus V=0 V=1 V=2 V=3 V=4 V=5 V=6 4v 9 5v 9 O-H Stretch Feierabend et al., Chemical Physics Letters, 2006, 420, 438 - 442

10. Credit: Zeb Kramer 38.5 kcal/mol 47.2 kcal/mol Feierabend et al., Chemical Physics Letters, 2006, 420, 438 - 442

11. Credit: Zeb Kramer 38.5 kcal/mol 47.2 kcal/mol Feierabend et al., Chemical Physics Letters, 2006, 420, 438 - 442 Explains SO 2 vertical profile on Earth

12. Zhang et al. Icarus, Volume 217, Issue 2, 2012, 714 - 739 Include UV Cross Section Debate on Effect of Water Clustering Lab Measurements of J values are needed Sulfuric Acid Cross Section

13. Voegele et al. (2002) “About the Stability of Sulfurous Acid and its dimer,” Chem. Eur. J. 8, 24, 5644-5651. H 2 SO 3 + n H 2 O SO 2 + (n+1)H 2 O

14. iHR550 Spectrometer with UV Sensitized CCD Energetiq Laser Driven Light Source Glass Cell with Quartz Windows Iris

15. +

16. + H 2 O?

17. Pure SO 2

18. Pure Water

19. Pure SO 2 Pure Water SO 2 + Water (varied)

20. Pure SO 2 Pure Water SO 2 + Water (varied)Water + SO 2 (varied)

22. Cell Window pH~3 Clean Window pH~7

23. CRD Nd:YAG Dye Laser SO 2 + H 2 O + H 2 SO 3 H2OH2O Xe Arc Lamp

24. CEAS Red Photochemical Lamp SO 3 + H 2 O H 2 SO 4 + H2OH2O SO 2 + H 2 O H 2 SO 3 + H2OH2O Energetiq LDLS J J

25. Dye Laser Nd:YAG Energetiq LDLS CEAS CRD

26. Vaida Group Members– Allison Harris, Rebecca Rapf, Russell Perkins Steve Brown – NOAA NSF Grant Number CHE1306386 Contact: Jay.Kroll@colorado.edu