纳米离子探针分析在地球早期生命研究中的应用

地球早期生命的个体极其微小,又因遭受了漫长地质年代中各种地质作用的破坏,现今保存下来的生命记录往往不完整,很难用常规分析手段对其进行原位分析.而纳米离子探针(Nano-SIMS)具有极高的空间分辨率,在使用Cs+一次离子源来获得非金属元素或同位素信息的条件下,其空间分辨率可达到50 nm,能有效地解决在地球早期生命研究中所面临的难题.基于选取的5个实例,介绍了NanoSIMS在寻找地球早期生命中发挥的重要作用.通过NanoSIMS获得的生命元素(C,N,S等)分布图像能够直观地观察到生命元素在待研究区域内的分布情况,在排除了无机成因的前提下,C,N,S等生命元素所呈现出的紧密联系可以用来指示生物成因；而获得的微区原位的C,S等同位素信息能够进一步帮助判断所谓的“生物体”或“生物遗迹构造”等是否是真正的生物或由生物活动造成的.

Application of Nano Ion Microprobe In-situ Analysis in the Evolution of Earth's Early Life

When life arose on Earth is an unresolved scientific issue, Therefore, it is of great significance to explore the origin of life on Earth and search for possible extraterrestrial life by identifying early life. Morphological or chemical features of life are the most compelling evidence for biogenic in origin. However, morphology is not sufficient to prove biogenicity, as many inorganic processes can result in similar features. In addition, the earliest life on Earth were extremely small and poorly preserved because they went through various geological destructive processes in the long geological time, so it is very difficult to use conventional analytical methods to study those early life in situ. Fortunately, NanoSIMS has very high spatial resolution. And with Cs+ primary ion source that is used to gain non metal elements or isotope information, its spatial resolution can promote to 50 nm, which can effectively solve the problems of early life on Earth we are facing. In this paper, five study examples related to early life are presented, which show the great important role NanoSIMS plays in searching for early life.
By using the life related element (like C, N, S) distribution images obtained by NanoSIMS, we can directly observe the distribution of the life-related elements (like C, N, S) in the study area. And after excluding the biogenic processes, the close relationship among C, N, S and other elements indicates a biological origin;
at the mean time, C and S isotope data of the obtained micro in situ area can further help to determine whether the so called “organism” is a true organism or “biological trails” is truly caused by biological activities.