火星快车OMEGA高光谱探测矿物组成的新进展

Progresses in OMEGA/Mars Express Detecting Minerals on Mars

主要介绍"火星快车(Mars Express)"搭载的"可见光及红外矿物制图光谱仪(OMEGA)"及其采集数据的特点、大气校正方法和矿物识别研究的新进展。"经验传输函数法"(ETF)是目前O-MEGA数据大气校正普遍采用的方法。OMEGA数据已经成功揭示了火星表面矿物和组成的多样性和复杂性。OMEGA检测到与水蚀变相关的层状硅酸盐矿物绿脱石、绿泥石和蒙脱石等主要分布于古老的诺亚期的露头上,这些层状硅酸盐矿物可能是火成岩矿物长期持续与液态水系统作用的结果。含水硫酸盐类矿物石膏、水镁矾和多水硫酸盐等水合化学沉积矿物在亮色调层状地层区的发现,表明火星表面有大量与水作用相关的蒸发盐的存在。火星表面缓慢风化形成的无水铁氧化物主要分布于北半球铁镁质含量低的低地(lowland)地区。OMEGA可以识别辉石和橄榄石,能够区分高钙辉石和低钙辉石。高钙辉石主要分布于Hesperian期的低反照率的火山岩分布地区、黑色沙丘和撞击坑喷射物分布区;低钙辉石主要分布于老的诺亚期的亮色调露头分布区。OMEGA在反照率变化大的极地冰盖地区可以识别水冰和CO2冰。水冰主要利用1.08μm、1.25μm、1.51μm和2.0μm特征吸收波段来识别。水冰各吸收特征波段的吸收强度与水冰的粒度呈正相关。CO2冰主要利用1.43μm、2.0μm和2.6μm特征吸收波段来识别。

The paper mainly introduces the features of OMEGA/Mars Express instrument and acquired data,the atmospheric correction methods,and recent progresses of mineral detection. Empirical Transmission Functions （ ETF） is the relative effective atmospheric correction method up to now. The OMEGA data have successfully revealed the diversity and complex of Mars surface minerals and composition. The hydrated phyllosilicates,a family of aqueous alteration products,such as nontronite,chlorite and montmorillonite,are detected by OMEGA. These minerals are mainly associated with Noachian outcrops,which are consistent with an early active hydrological system,sustaining the long-term contact of igneous minerals with liquid water. The hydrated sulfates,such as gypsum,kieserite and polyhydrated sulfates,are identified on light-toned layered terrains. The existence of these minerals means that there have evaporates deposits on Mars which are related to water processes. Anhydrous ferric oxides formed in a slow superficial weathering are distributed in lowland over the northern hemisphere,without liquid water playing a major role across the planet. OMEGA can identify pyroxene and olivine. It discriminates between the high-calcium pyroxenes and low-calcium pyroxenes. The high-calcium pyroxenes dominate in low-albedo volcanic regions of Hesperian age,dark sand and crater ejecta. The low-calcium pyroxenes occur as moderate to bright outcrops in older,Noachian terrains. OMEGA can also discriminate the H2O ice and CO2 ice in varied high-albedo polar icecap area. The H2O ice absorption features are major in the 1. 08 m,1. 25 m,1. 51 m and 2. 0 m. The H2O ice absorption depth increases with the ice grain size. The CO2 ice can be identified by 1. 43 m,2. 0 m and 2. 6 m absorption features.