Development of micro-analytical methods
Stable Carbon Isotope analysis of TEM sections by means of Nuclear Microprobe Rutherford Backscattering Stable carbon isotopes play an important role in the interpretation of biological activity, particularly when the fossil record includes morphological and chemical signatures of life.  Isotopic information is therefore a useful tool in paleontological and astrobiological studies. Dr. Tomas Hode and his collaborators are developing a new non-destructive microanalytical nanoscale ion beam system for measurement of stable carbon isotope ratios in TEM samples with high spatial resolution and good counting/detection statistics.  The technique is based on elastic scattering of alpha particles with an energy of 2.75 MeV.  At this particular energy, there is a resonance effect in which the nuclear wave functions interact so that the 13C cross-section is enhanced relative to the pure Rutherford cross-section, whereas the 12C cross section is reduced.  The method is a valuable complement to other micro- or nano-analytical methods for the following reasons: (1) It is a non-destructive method particularly suited for micro/nano-analysis of extraterrestrial and other rare or irreplaceable material, (2) There are no matrix effects associated with the method. Thus, any type of solid material can be analyzed, including biological material. (3) Nuclear isotope measurements can be taken from specimens prepared for transmission electron microscopy, which can result in the acquisition of isotopic, imaging, diffraction, and spectroscopic analyses of the same object in a TEM specimen. The implications of this method are of particular interest in martian exploration research, especially for the analysis of samples returned from Mars. Any material delivered from the red planet would be considered extremely valuable, especially if there was evidence that the material might contain possible microfossils or other microbial biosignatures. Though destructive analytical methods would harm or destroy valuable samples, the methods being developed in this study provide a means to obtain carbon isotope data from microscopic samples non-destructively. A New Method for (Single) Fluid Inclusion Extraction Fluid inclusions in rocks and minerals may hold valuable information about the temperature and composition of the fluids from which the minerals precipitated. Low-temperature mineralizations from fluids that contain organic phases are of special interest for astrobiologists since they may act as sealed containers of non-contaminated organic matter with a defined minimum age. Most techniques for characterizing such fluid inclusions are indirect, and involve freezing and heating the sample to study homogenization temperatures and composition of the fluid, Raman analysis of solid phases, and fluorescence spectroscopy of organic phases. To perform often needed direct analysis of the fluid content, it has been necessary either to crush the sample or to heat it, with subsequent decrepitation of the inclusions, to extract the fluids. However, the primary disadvantage with crushing or heating a sample is that the mean composition of all fluid inclusions in the sample will be analyzed. No distinction can be made between primary and secondary inclusions. To date, the only way to open fluid inclusions in a controlled manner has been laser ablation, but that method has many disadvantages, particularly when it involves organic matter, and the technique has therefore not been fully explored. Dr. Hode has developed on a novel concept to extract single fluid inclusions without ablating the sample. The method is based on the illumination of selected fluid inclusions with a laser of a wavelength that is absorbed by water and organic material, but not the minerals encapsulating the fluid. Thus, when the laser illuminates the inclusion the fluid expands and the inclusion decrepitates. Since the sample is placed in a vacuum chamber, the fluid evaporates and may subsequently be collected either on a cooling trap or via a carrier gas that can transport it directly into an apparatus for analysis. An additional advantage with Dr. Hode’s new method is the potential to avoid contamination of the analyzed hydrocarbons. Since fluid inclusions act as sealed vessels, the chemical composition of the fluid stays intact until the vessel has been opened. The sample can thus be handled and prepared in any desired way (often as doubly polished thin sections) without contaminating the fluid before the extraction takes place. The biggest difficulty is actually analyzing the very small amount of material trapped in fluid inclusions. Dr. Hode is currently supervising a student who is working on a project to use the ToF-SIMS (Time of Flight Secondary Mass Spectrometry) as a way of analyzing extremely small amounts of hydrocarbons trapped inside fluid inclusions.