SIMS remote analysis of the Phobos surface: The DION experiment

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was introduced into cosmochemistry about a decade ago. Major advantages of TOF-SIMS compared to other ion microprobe techniques are (a) parallel detection of all secondary ions with one polarity in a single measurement—both polarities in subsequent analyses, (b) high lateral resolution, (c) sufficient mass resolution for separation of major mass interferences, and (d) little sample destruction. This combination makes TOF-SIMS highly suitable for the analysis especially of small samples, like interplanetary and presolar dust grains, as well as tiny inclusions within meteorites. Limitations of this technique are mainly referring to isotopic measurements and quantification. The possibility to measure molecular and atomic ion species simultaneously extends the applications of TOF-SIMS to the investigation of indigenous hydrocarbons in extraterrestrial material, which might have been essential for the formation of life. The present work gives an overview of TOF-SIMS in cosmochemistry, technical aspects as well as applications, principles of data evaluation and various results.