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Aubrey AD Chalmers JH Bada JL Grunthaner FJ Amashukeli X Willis P Skelley AM Mathies RA Quinn RC Zent AP Ehrenfreund P Amundson R Glavin DP Botta O Barron L Blaney DL Clark BC Coleman M Hofmann BA Josset JL Rettberg P Ride S Robert F Sephton MA Yen A 《Astrobiology》2008,8(3):583-595
The Urey organic and oxidant detector consists of a suite of instruments designed to search for several classes of organic molecules in the martian regolith and ascertain whether these compounds were produced by biotic or abiotic processes using chirality measurements. These experiments will also determine the chemical stability of organic molecules within the host regolith based on the presence and chemical reactivity of surface and atmospheric oxidants. Urey has been selected for the Pasteur payload on the European Space Agency's (ESA's) upcoming 2013 ExoMars rover mission. The diverse and effective capabilities of Urey make it an integral part of the payload and will help to achieve a large portion of the mission's primary scientific objective: "to search for signs of past and present life on Mars." This instrument is named in honor of Harold Urey for his seminal contributions to the fields of cosmochemistry and the origin of life. 相似文献
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Jean-Luc Widlowski Thomas Lavergne Bernard Pinty Nadine Gobron Michel M. Verstraete 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,41(11):1724-1732
The divergence of horizontal radiation in vegetation canopies is generally considered to be of negligible consequence in algorithms designed for the physically-based interpretation of space borne observations. However, non-zero horizontal radiation balances are likely to occur if the internal variability of a vegetation target and the typical distances that photons may travel horizontally within such three-dimensional (3-D) media extend to spatial scales that are similar to or larger than those of the nominal footprint of the measuring sensor. Detailed radiative transfer simulations in 3-D coniferous forest environments are presented to document the typical distances that photons may travel in such media, and to quantify the impact that the resulting net horizontal fluxes may have with respect to the local and domain-averaged canopy reflectance. Based on these simulations it is possible to identify a fine spatial resolution limit beyond which pixel-based interpretations of remote sensing data over tall forested areas should be avoided because the horizontal radiation transport at the surface may contribute to 10% or more of the measured reflectance signature of the target pixel. 相似文献
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