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William R. Sheldon, Ph.D., Professor, and
James R. Benbrook, Ph.D., Professor, Department of Physics, UH
The University of Houston Ozone Program is proceeding along three directions: (1) investigation of ozone depletion in the lower stratosphere in the exhaust plumes of large rockets, (2) investigation of ozone depletion in the upper stratosphere at sunrise, and (3) investigation of the Earth's history based on the paleontological record and the requirement that organisms living at the Earth's surface need an ozone layer for protection from solar ultraviolet (UV) radiation.
The investigation of large booster rockets is part of the RISO (Rocket Impacts on Stratospheric Ozone) program in collaboration with The Aerospace Corporation and other investigators. The measurements are conducted onboard a WB57F aircraft that operates above 60,000 feet. To date, we have investigated six launches: three Titan IV's, two Space Shuttles, and one Delta. From a twilight observation we have determined that ozone destruction in a Titan plume requires daylight, an indication that photolytic processes are involved.[1] From the two daylight Titan investigations, the temporal and spatial aspects of ozone destruction in the exhaust were measured.[2]
An observation of a significant amount of ozone destruction at 40 km at sunrise from a balloon flight in France was reported in the Journal of Atmospheric and Solar-Terrestrial Physics.[3] This measurement is important because it represents a rare instance of dynamic photochemistry in action. Our French colleagues at the Service d'Aéronomie du CNRS suggested that the measurement be repeated. To this end, we prepared a proposal to the Texas Higher Education Coordinating Board which has been supported. Discussions are currently underway with French colleagues regarding this campaign which is expected to be performed during the coming two years. In the meantime, Shyam Munshi, an undergraduate physics student, is working on a computer program to calculate ozone photochemistry at sunrise.
The requirement that living organisms need protection from solar UV radiation in order to live at the Earth's surface, or in shallow seas, provides a unique perspective for interpreting the Earth's paleontological record. Prof. Sheldon collaborated on a paper in Origins of Life[4] and has presented papers on various aspects of this topic to four international conferences in 1996 and 1997. Another presentation will be delivered to the December, 1997 meeting of the American Geophysical Union on "The Cambrian Explosion Paradox."
References
[1]Geophys. Res. Lett. (1997).
[2]M. N. Ross, J. R. Benbrook, and J. R. Mckenzie. "Observation of Stratospheric
Ozone Depletion in Rocket Exhaust Plumes," Nature 390 (Nov. 1997): 62-64.
[3]J. Atmos. Solar-Terr. Phys. 59 (Jan. 1997): 1-7.
[4]Origins of Life 27 (1997): 413-20.
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