Dalton James Bradley
SETI Institute, NASA Ames Research Center, Moffett Field, California 94035-1000, USA.
Astrobiology. 2003 Winter;3(4):771-84. doi: 10.1089/153110703322736097.
Remote sensing of the surface of Europa with near-infrared instruments has suggested the presence of hydrated materials, including sulfate salts. Attention has been focused on these salts for the information they might yield regarding the evolution of a putative interior ocean, and the evaluation of its astrobiological potential. These materials exhibit distinct infrared absorption features due to bound water. The interactions of this water with the host molecules lead to fine structure that can be used to discriminate among these materials on the basis of their spectral behavior. This fine structure is even more pronounced at the low temperatures prevalent on icy satellites. Examination of hydrated sulfate salt spectra measured under cryogenic temperature conditions provides realistic constraints for future remote-sensing missions to Europa. In particular, it suggests that a spectrometer system capable of 2-5 nm spectral resolution or better, with a spatial resolution approaching 100 m, would be able to differentiate among proposed hydrated surface materials, if present, and constrain their distributions across the surface. Such information would provide valuable insights into the evolutionary history of Europa.
利用近红外仪器对木卫二表面进行遥感探测表明存在水合物质，包括硫酸盐。人们一直关注这些盐类，因为它们可能提供有关假定内部海洋演化以及评估其天体生物学潜力的信息。由于结合水的存在，这些物质呈现出独特的红外吸收特征。这种水与主体分子的相互作用导致了精细结构，可根据其光谱行为用于区分这些物质。在冰卫星普遍存在的低温下，这种精细结构更为明显。对在低温条件下测量的水合硫酸盐光谱进行研究，为未来前往木卫二的遥感任务提供了现实的限制。特别是，这表明一个光谱分辨率能够达到2 - 5纳米或更高，空间分辨率接近100米的光谱仪系统，如果存在提议的水合表面物质，将能够区分它们，并限制它们在表面的分布。这些信息将为木卫二的演化历史提供有价值的见解。
