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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 - BoulderJune 20, 2014
Photo Credit: J. Gabás Esteban
• Sulfur compounds have been observed on a number of planetary bodies.
Background/Motivation
Photo credit: ESA
Venus Earth Mars
Io EuropaCallisto
Background/Motivation• 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
Background/Motivation
Belyaev et al. Icarus, Volume 217, Issue 2, 2012, 740 - 751
Mixing Ratio (ppmv)
Altit
ude
(km
)
SO2
SO
• Sulfur compounds have been observed on a number of planetary bodies.
• Venus– Sulfuric acid clouds 50-70 km
– Increase in SO2 at 90 km
– Exceeds model predictions by orders of magnitude
Background/Motivation
Belyaev et al. Icarus, Volume 217, Issue 2, 2012, 740 - 751
Mixing Ratio (ppmv)
Altit
ude
(km
)
SO2
SO
• Sulfur compounds have been observed on a number of planetary bodies.
• Venus– Sulfuric acid clouds 50-70 km
– Increase in SO2 at 90 km
– Exceeds model predictions by orders of magnitude
– Requires a chemical source of SO2 in the middle atmosphere
• UV photolysis of H2SO4
UV Photolysis?
H2SO4 + UV SO3+H2O SO3 + UV SO2+O
• UV photolysis of H2SO4
UV Photolysis?
H2SO4 + UV SO3+H2O SO3 + UV SO2+O
Lane and Kjaergaard, J Phys. Chem A. 2008, 112, 4958-4964
180 nmSulfuric Acid Cross Section
• UV photolysis of H2SO4
UV Photolysis?
H2SO4 + UV SO3+H2O SO3 + UV SO2+O
Lane and Kjaergaard, J Phys. Chem A. 2008, 112, 4958-4964
180 nmSulfuric Acid Cross Section Spectral Actinic Flux of Venus
Zhang et al. Icarus, Volume 217, Issue 2, 2012, 714 - 739
58 km 70 km112 km
Red Light Photolysis
V=0
V=1
V=2
V=3
V=4
V=5
V=6
4v9
5v9
O-H Stretch
Feierabend et al., Chemical Physics Letters, 2006, 420, 438 - 442
Credit: Zeb Kramer
38.5 kcal/mol
47.2 kcal/mol
Feierabend et al., Chemical Physics Letters, 2006, 420, 438 - 442
Red Light Photolysis
Credit: Zeb Kramer
38.5 kcal/mol
47.2 kcal/mol
Feierabend et al., Chemical Physics Letters, 2006, 420, 438 - 442
Red Light Photolysis
Explains SO2 vertical profile on Earth
Does It Explain SO2 on Venus?
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
Sulfurous Acid
Voegele et al. (2002) “About the Stability of Sulfurous Acid and its dimer,” Chem. Eur. J. 8, 24, 5644-5651.
H2SO3 + n H2O SO2 + (n+1)H2O
New UV Spectrometer
iHR550 Spectrometer
with UV Sensitized CCD
Energetiq Laser Driven Light
Source
Glass Cell with Quartz Windows
Iris
First Test - June 2nd
+
First Test - June 2nd
+
H2O?
Recent ResultsPure SO2
Recent ResultsPure SO2 Pure Water
Recent ResultsPure SO2 Pure Water
SO2 + Water (varied)
Recent ResultsPure SO2 Pure Water
SO2 + Water (varied) Water + SO2 (varied)
Recent Results
Recent Results
Cell WindowpH~3
Clean WindowpH~7
Future Work
CRD
Nd:YAG
Dye Laser
SO2 + H2O + H2SO3H2O
Xe Arc Lamp
Future Work
CEAS
Red Photochemical
Lamp
SO3 + H2OH2SO4 +H2O
SO2 + H2OH2SO3 + H2O
Energetiq LDLS
J
J
Future Work- Experiments
Dye Laser
Nd:YAG
Energetiq LDLS
CEAS
CRD
AcknowledgementsVaida Group Members– Allison Harris, Rebecca Rapf, Russell Perkins
Steve Brown – NOAA
NSF Grant Number CHE1306386
Contact: [email protected]
