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The Formation of Sulfate and Elemental Sulfur Aerosols Under Varying Laboratory Conditions: Implications for Early EarthThe presence of sulfur mass-independent fractionation (S-MIF) in sediments more than 2.45 x 10(exp 9) years old is thought to be evidence for an early anoxic atmosphere. Photolysis of sulfur dioxide (SO2) by UV light with lambda < 220 nm has been shown in models and some initial laboratory studies to create a S-MIF; however, sulfur must leave the atmosphere in at least two chemically different forms to preserve any S-MIF signature. Two commonly cited examples of chemically different sulfur species that could have exited the atmosphere are elemental sulfur (S8) and sulfuric acid (H2S04) aerosols. Here, we use real-time aerosol mass spectrometry to directly detect the sulfur-containing aerosols formed when SO2 either photolyzes at wavelengths from 115 to 400 nm, to simulate the UV solar spectrum, or interacts with high-energy electrons, to simulate lightning. We found that sulfur-containing aerosols form under all laboratory conditions. Further, the addition of a reducing gas, in our experiments hydrogen (H2) or methane (CH4), increased the formation of S8. With UV photolysis, formation of S8 aerosols is highly dependent on the initial SO2 pressure; and S8 is only formed at a 2% SO2 mixing ratio and greater in the absence of a reductant, and at a 0.2% SO2 mixing ratio and greater in the presence of 1000 ppmv CH4. We also found that organosulfur compounds are formed from the photolysis of CH4 and moderate amounts of SO2, The implications for sulfur aerosols on early Earth are discussed.
Document ID
20110012866
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
DeWitt, H. Langley
(Colorado Univ. Boulder, CO, United States)
Hasenkopf, Christa A.
(Colorado Univ. Boulder, CO, United States)
Trainer, Melissa G.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Farmer, Delphine K.
(Colorado Univ. Boulder, CO, United States)
Jimenez, Jose L.
(Colorado Univ. Boulder, CO, United States)
McKay, Christopher P.
(NASA Ames Research Center Moffett Field, CA, United States)
Toon, Owen B.
(Colorado Univ. Boulder, CO, United States)
Tolbert, Margaret A.
(Colorado Univ. Boulder, CO, United States)
Date Acquired
August 25, 2013
Publication Date
January 1, 2010
Publication Information
Publication: Astrobiology
Volume: 10
Issue: 8
Subject Category
Geophysics
Report/Patent Number
GSFC.JA.4364.2011
Funding Number(s)
CONTRACT_GRANT: NNX07AV55G
Distribution Limits
Public
Copyright
Other

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