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Stability of hydroxylated minerals on Mars: A study on the effects of exposure to ultraviolet radiation

Yen, Albert S. and Murray, Bruce and Rossman, George R. and Grunthaner, Frank J. (1999) Stability of hydroxylated minerals on Mars: A study on the effects of exposure to ultraviolet radiation. Journal of Geophysical Research E, 104 (E11). pp. 27031-27041. ISSN 0148-0227. doi:10.1029/1999JE001065.

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The density and composition of the Martian atmosphere allow solar ultraviolet photons with wavelengths as short as 190 nm to reach the surface. We investigate the hypothesis that this UV radiation is capable of inducing the release of water from iron oxyhydroxide minerals resulting in the formation of oxide phases. These experiments, which utilize a quadrupole mass spectrometer to monitor the water vapor pressure above mineral samples during cyclic exposure to ultraviolet radiation, offer 5 to 6 orders of magnitude greater sensitivity than previous attempts to establish and quantify this process. We find no evidence that UV photons are capable of liberating OH from the crystal lattice of minerals, and we set a minimum ultraviolet radiation-induced dehydroxylation time of 10^8 years for removal of this structural OH from mineral particles at the Martian surface. The overturning timescales for surface fines are likely to be shorter than this lower limit for exposure time. Thus we conclude that UV-stimulated dehydroxylation is not a significant process at the Martian surface and that iron oxyhydroxides, if formed during an earlier water-rich environment, should still be found on Mars today. The lack of clear evidence for iron oxyhydroxides at the Martian surface further suggests that Mars' surface was never warm and wet for a long enough period of time for Earth-like weathering to have occurred.

Item Type:Article
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Rossman, George R.0000-0002-4571-6884
Additional Information:© 1999 American Geophysical Union. Received April 9, 1999; revised August 31, 1999; accepted September 9, 1999. We thank Natasha Johnson and an anonymous referee for providing careful and perceptive reviews of the initial manuscript. We wish to thank the MicroDevices Laboratory at the Jet Propulsion Laboratory for providing the facilities and equipment to conduct these experiments. A. Y. was supported by the NASA Graduate Student Researchers Program (NGT5-50125). The research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
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NASA Graduate Student Researchers ProgramNGT5-50125
Issue or Number:E11
Record Number:CaltechAUTHORS:20130415-152214853
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Official Citation:Yen, A. S., B. Murray, G. R. Rossman, and F. J. Grunthaner (1999), Stability of hydroxylated minerals on Mars: A study on the effects of exposure to ultraviolet radiation, J. Geophys. Res., 104(E11), 27031–27041, doi:10.1029/1999JE001065
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:37951
Deposited By: Tony Diaz
Deposited On:17 Apr 2013 16:36
Last Modified:09 Nov 2021 23:32

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