HR: 0800h
AN: P51D-0953    [Abstracts]
TI: Photosynthesis via Mineral Fluorescence in Harsh UV Radiation Environments
AU: Barge, L M
EM: barge@usc.edu
AF: University of Southern California, 3651 Trousdale Parkway, Los Angeles, CA 90089 United States
AU: * Nealson, K
EM: knealson@usc.edu
AF: University of Southern California, 3651 Trousdale Parkway, Los Angeles, CA 90089 United States
AB: Before the development of a protective ozone layer about two billion years ago, the surface ultraviolet flux on Earth would have restricted ancient life to environments that offered some protection from direct solar radiation, such as the deep ocean or under or within rocks. In environments where the visible solar radiation would have been reduced to levels too low for photosynthesis, visible fluorescence resulting from UV irradiation of minerals may have provided a useable energy source. We are investigating the possibility that photosynthesis can occur without direct sunlight, if certain minerals are present that can absorb UV radiation and fluoresce in the visible. There are several common minerals(e.g. fluorite, calcite) that emit strong visible radiation under both short- and long-wave UV light, as well as some that only emit visible radiation under specific UV wavelengths. We will test a variety of minerals that fluoresce at wavelengths utilized by microbial chlorophylls and accessory pigments, and by simulating endolithic communities living under a few centimeters or millimeters of rock, we will measure the intensity of fluorescence and UV radiation received at various depths. We plan to simulate a variety of environments where the surface UV radiation may have a significant impact on the survival of life. These include the early Earth and present-day Mars(where the atmosphere would offer little to no protection against biologically damaging UV radiation), as well as extrasolar planets(a terrestrial planet in the habitable zone around an M-type star, for example, would be subject to an intense UV flux due to high flare activity). If mineral fluorescence proves to be a viable survival mechanism for photosynthetic organisms in harsh radiation environments, there are many implications for the study of ancient life on Earth as well as the search for life elsewhere.
DE: 0456 Life in extreme environments
DE: 3699 General or miscellaneous
DE: 5225 Early environment of Earth
SC: Planetary Sciences [P]
MN: Fall Meeting 2005