Experimental constraints on the formation of oxychlorine species by UV irradiation and mechanical pulverization on the lunar surface

Perchlorate and chlorate are present in various extraterrestrial celestial bodies throughout the solar system,such as Mars,the moon,and asteroids.To date,the origin mechanisms of perchlorate and chlorate on the Martian surface have been well-established;however,relatively little attention has been cast to airless bodies.Here,we experimentally investigated the potential oxidation mechanisms of chloride to chlorate and perchlorate,such as ultraviolet irradiation under H_(2)O-and O_(2)-free conditions and mechanical pulverization processes.Individual minerals,olivine,pyroxene,ilmenite,magnetite,TiO_(2)and anhydrous ferric sulfate,and lunar regolith simulants(low Ti,CLRS-1;high-Ti,CLRS-2)and their metallic iron(Fe^( 0))bearing counterparts were examined.We found that pulverization of dry matrix material-halite mixtures,even in the presence of O_(2),does not necessarily lead to perchlorate and chlorate formation without involving water.Under photocatalytic and H_(2)O and O_(2)-free conditions,olivine and pyroxene can produce oxychlorine(ClO_(x)^(−))species,although the yields were orders of magnitude lower than those under Martian-relevant conditions.Nanophase-Fe^(0)particles in the lunar regolith and the common photocatalyst TiO_(2)can facilitate the ClO_(x)^(−)formation,but their yields were lower than those with olivine.The oxides ilmenite and magnetite did not efficiently contribute to ClO_(x)^(−)production.Our results highlight the critical role of H_(2)O in the oxidation chloride to chlorate and perchlorate,and provide essential insights into the environmental influence on the formation of oxychlorine species on different celestial bodies.

国际火星探测科学目标演变与未来展望

火星探测是当前太阳系探测和行星科学的焦点.经过近60年的发展,火星成为除地球外,探测和研究程度最高的太阳系行星体,派生出火星空间环境、火星大气、火星表层/次表层物质组成、形貌构造、撞击历史、冰川和冰冻层、气候变化、火星内部结构等多个研究领域.火星陨石研究和实验室模拟研究(实验模拟、数值模拟等)也得以快速发展.火星的重大科学发现包含早期和现代的水活动证据、地质环境多样性、现代地质过程监测、甲烷和有机物的发现、大气组成和演化、当前和近期气候变化、重力场和表面辐射环境等.重大科学成果的取得得益于科学目标规划的指引,也影响着未来科学目标的制订.通过梳理美国火星探测项目分析组(Mars Exploration Program Analysis Group,MEPAG)近20年火星探测科学目标(生命、气候、地质、载人)的演变,展现出国际火星探测思路及未来探测重点.未来10年的火星探测将进一步认知火星内部结构、开启火星生命探测的新阶段和开展火星和火星卫星样品返回.中国开展的火星探测任务也将为国际火星科学发展做出贡献.当前火星仍有诸多重大科学问题未有解答,这些问题与太阳系的重大科学问题紧密融合,突显出火星探测在太阳系形成演化以及太阳系行星宜居性的形成演化研究中不可替代的重要地位.