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.