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Techniques used for the ISAR project:
Optical microscopy of thin sections is widely used in geology for characterizing petrology and petrography. For space exploration, high magnification imaging (camera) and optical microscopy are carried out on rough and abraded surfaces or powders.
X-Ray diffraction is used to measure the lattice parameters of a mineral in order to identify it. This technique is generally used on powdered sample but can also be used on bulk samples or thin sections. It will be used on Mars during the MSL mission (APXS device) and the Mars 2018 mission (Mars-XRD).
Infrared spectroscopy is used to identify mineral and organic phases in a sample from the vibration spectra of the molecules that make up of components of the sample. In geology laboratories, this technique is mostly used in transmission on a pellet made of powdered sample and KBr but analysis in reflectance on powdered sample, thin section or bulk sample is also possible. A large part of the mineralogical data from Mars was obtained from the orbit by IR spectroscopy (MRO, Mars Express). This technique is widely used for space exploration (MSL, Mars 2018, Rosetta…).
Raman spectroscopy uses a laser to identify mineral and organic phases in a sample from the vibration spectra of the molecules making up the components. It is a non destructive method and it can be used on bulk samples, thin sections or powders. 2D and 3D compositional maps of a sample can be made using a confocal scanning system. A Raman spectrometer will be used during the Mars 2018 mission.
Scanning electron microscopy uses an electron beam to scan the surface of a sample in order to make very high resolution, nm-scale imaging. Due to the interactions of the electrons with the matter, this technique can also be used to make elemental analyses by EDX for instance. SEMs have yet not been miniaturized for space exploration.
Electronic microprobe is a spectroscopic method using the X-ray emitted during the interaction of an electron beam with the matter to determine the elementary composition of a sample (structural formulae of minerals ) with very high precision. By scanning the surface it is also possible to obtain chemical element mapping. Electron microprobes have not been miniaturized for space exploration.
The Mössbauer spectrometry used gamma ray radiation to determine the degree of oxidation and the chemical environment of elements in a sample. The technique is widely used for the study of iron minerals. The MERs Sprit and Opportunity and the probe Beagle 2 were equipped with Mössbauer spectrometers.
The cathodoluminescence is used to detect trace elements and crystalline defects in minerals using the photoluminescence of the sample induced by an electron beam. It can be used on thin sections or hand samples. Cathodoluminescence has not yet been used for space exploration but it could equip a probe in the near future.
Inductively coupled plasma spectrometry is used to make the elemental composition analyses. Elements ionized by nitrogen plasma are analyzed by two main types of techniques: optical emission spectroscopy (ICP-OES ) for the major elements and mass spectroscopy (ICP-MS ) for traces elements. ICP has not yet been sent into space.