HR: 1340h
AN: OS43B-0556    [Abstracts]
TI: Laser-induced Native Fluorescence Detection of Organic Molecules in Hydrothermal Vent Rocks
AU: * Harju, E
EM: harjue@u.washington.edu
AF: University of Washington, 1410 NE Campus Parkway, Seattle, WA 98195
AU: Kidd, R D
EM: richard.d.kidd@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109
AU: Bhartia, R
EM: Rohit.Bhartia@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109
AU: Conrad, P G
EM: conrad@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109
AB: We have developed a Multi-channel Deep Ultraviolet Excitation (McDuve) fluorescence detector that has been deployed at several Pacific hydrothermal vent sites [1]. The in situ McDuve detector was able to detect organic molecules at the vent site on rock surfaces and in the water, the signatures being distinguishable one from the other. The McDuve fluorescence detector uses a 224.3 nm helium-silver hollow cathode laser to induce native fluorescence from a sample. Spectral separation is achieved with optical band-pass filters which are coupled to photomultiplier tubes (PMTs) for detection. Samples were recovered at the vent sites and returned from the expedition for bench-top analysis for correlation of the McDuve observations with standard analytical tools-GCMS and X-ray diffraction (for mineralogical ID), as well as with a bench-top version of the McDuve fluorescence detector. Here we report the corroborative results of the laboratory studies. Several preserved samples were subjected to 224.3 nm ultraviolet excitation under wet and dry conditions. Organic molecules were detected on the wet samples analyzed in the lab, corroborating the in situ McDuve data. The fluorescence emission wavelengths associated with the detected organic molecules suggest they are 3-5 ring polycyclic aromatic hydrocarbons [2,3]. The samples were also pyrolized at 500 §C to decompose any organic molecules present and subsequently reanalyzed. This McDuve analysis revealed a significant decrease in laser induced native fluorescence, a result consistent with the pyrolytic decomposition of the organic content of the rock samples. [1] Conrad, P.G., A.L. Lane, R. Bhartia, W. Hug, (March 2004) Optical Detection of Organic Chemical Biosignatures at Hydrothermal Vents 35th Lunar Plan. Sci. XXXV, 2055. [2] Karcher, W. (1985), Spectral Atlas of Polycyclic Aromatic Compounds, vol. I, Kluwer Academic Publishing Company, Dordrecht, Holland. [3] Bhartia, R., McDonald, G.D., Salas, E.C., Hug, W., Reid, R., Conrad, P.G., (2004) A Model to Differentiate Organic Compounds Based on UV Fluorescence Spectroscopy, Intl. J. Astrobiology, Suppl. 1, 115-116
DE: 4815 Ecosystems, structure and dynamics
DE: 3015 Heat flow (benthic) and hydrothermal processes
DE: 3035 Midocean ridge processes
DE: 1020 Composition of the crust
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting