HR: 0800h
AN: P51B-0489    [Abstracts]
TI: Highly Oxidizing Surface Radicals in Lunar Dust
AU: * Kulahci, I
EM: ipek.kulahci@gmail.com
AF: Carl Sagan Center SETI Institute, 515 N Whisman Rd., Mountain View, CA 94043, United States
AU: Freund, F T
EM: ffreund@mail.arc.nasa.gov
AF: Carl Sagan Center SETI Institute, 515 N Whisman Rd., Mountain View, CA 94043, United States
AU: Freund, F T
EM: ffreund@mail.arc.nasa.gov
AF: NASA Ames Research Center, Code SGE, Moffett Field, CA 94035-1000, United States
AU: Freund, F T
EM: ffreund@mail.arc.nasa.gov
AF: San Jose State University, Department of Physics, San Jose, CA 95192-0106, United States
AU: Bose, M
EM: milton.bose@gmail.com
AF: Carl Sagan Center SETI Institute, 515 N Whisman Rd., Mountain View, CA 94043, United States
AU: Bose, M
EM: milton.bose@gmail.com
AF: UC Riverside, Department of Physics, Riverside, CA 92521, United States
AU: Loftus, D J
EM: djl@leland.stanford.edu
AF: NASA Ames Research Center, Code SCR, Moffett Field, CA 94035-1000, United States
AU: Loftus, D J
EM: djl@leland.stanford.edu
AF: Stanford University, Cancer Center, Stanford, CA 94305-5820, United States
AB: Lunar rocks are generally believed to be very "dry" with little or no evidence for hydroxyl as indicators of traces of dissolved H2O. The absence of hydroxyl, however, is not a sure sign of the absence of dissolved H2O. The reason is that hydroxyl pairs in the structure of host minerals, O3X-OH HO-XO3, with X=Si4+, Al3+ etc., tend to undergo an electronic rearrangement (redox conversion) in the course of which two oxygen anions are oxidized from the 2- to the 1- valence, forming a peroxy link, O3X-OO-XO3, plus an H2 molecule. If the H2 molecules diffuse out (which they are expected to do from lunar rocks and lunar fines over the course of 4 Gyrs), the peroxy links remain as the only "memory" of a former solute H2O content. Hard UV causes peroxy links to dissociate. In the process an electron from a neighboring O2– jumps into the broken peroxy bond. This is equivalent to forming an O–, e.g. a defect electron in the oxygen anion sublattice. Such defect electrons, also known as positive holes or pholes for short, represent highly mobile charge carriers. When trapped at the surface of dust grains, these charge carriers turn into highly reactive, highly oxidizing O– radicals, which are of concern because of their toxicity when lunar dust is inhaled by astronauts. We propose a device to measure the UV-activation of peroxy links by dusting lunar fines onto a polyethylene base plate with Au electrodes sputtered onto both ends and an ammeter connecting the two electrodes. One end of the dust layer will be exposed to the ambient UV radiation, while the remainder will be shaded. During the lunar night no current is expected to flow between the two Au electrodes. During passage through the night-day terminator, a current is expected to flow between the Au electrodes carried by defect electrons activated in the irradiated portion of the dust layer. Such a current would be an indicator that lunar fines and, by implication, lunar rocks contain peroxy links as a memory of a former solute H2O content.
DE: 5430 Interiors (8147)
DE: 6250 Moon (1221)
DE: 6297 Instruments and techniques
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting