土卫六Titan大气中多环芳香烃PAH分子

Polycyclic aromatic hydrocarbons in the atmosphere of Titan

土卫六(Titan)是土星的最大一颗卫星,也是太阳系第二大卫星.它是太阳系唯一一颗拥有浓厚大气层的卫星.其大气层富含氮气(N2,体积比占98%),少量甲烷(CH4,占2%)以及其他微量有机分子(如乙炔C2H2).最近,卡西尼(Cassini)宇宙飞船上的VIMS光谱仪对土卫六的大气层作了光谱观测,探测到源自多环芳香烃(PAH)分子的3.28?m发射特征.PAH是星际介质的重要成分,也常被认为是土卫六上空橘红色的烟雾层(Haze)的重要成分.PAH分子如何在土卫六大气中形成是行星科学的一个难解之谜.本文从星际空间、太阳系的PAH分子研究着手,介绍了Titan的大气中多环芳烃PAH分子的观测特性、化学结构、形成机制及未来趋势.

Titan is the largest satellite of Saturn and the second largest satellite in the solar system. It is the only satellite in the solar system that has a dense atmosphere. Its atmosphere is dominated by N2 （98% by volume）, with a small amount of CH4 （2% by volume） and tiny amounts of other organic molecules. Very recently, the Visual-Infrared Mapping Spectrometer （VIMS） on board the Cassini spacecraft detected in the atmosphere of Titan the 3.28 ~m emission feature which is believed to arise from the C-H stretching mode of polycyclic aromatic hydrocarbon （PAH） molecules PAHs are thought to be a major constituent of the Titan haze. How PAHs are formed in the Titan atmosphere is still a mystery. This paper discusses the observational properties, chemical structures, and formation mechanisms of PAHs in the atmosphere of Titan.