Homepage News Database Contact us
We distinguish five different types of analogue samples, namely analogues, witness plate, voucher specimen, reference sample, and standards.
Analogues are materials that have one or more physical or chemical properties similar to Earth-returned extraterrestrial samples.
Reference samples are well characterised materials with known physical/chemical properties used for testing of the whole process or part of it. They may not necessarily be the same materials as the analogues defined above.
Standards are internationally recognised, homogeneous materials with known physical/chemical properties that are used for calibration (e.g. silicon for Raman spectrometry). They can also be used as reference samples in certain circumstances. They may be made of natural materials (e.g. the Belemnitella americana from Pee Dee Formation in South Carolina, used for 13C isotope studies) but are often produced artificially (e.g. the calibration targets used on the instrument ChemCam in the MSL mission).
A voucher specimen is a duplicate of materials used at any stage during sample acquisition, storage, transport, treatment etc., e.g. space craft materials (including solar panels), lubricants, glues, gloves, saws, drills, and other, and stored for when needed. In addition, Earth landing site samples (from the touch down site) would be necessary in case of doubtful analysis even if normally this type of contamination is not expected (cf. Stardust).
A witness plate is defined material left in an area where work is being done or assessed for e.g. biological, particulate, chemical, and/or organic contamination. It is a spatial and temporal document of what happens in the work area.
Analogue materials could be solids, including ices, liquids or gases. These could contain biological (extant and/or extinct) and/or organic components. They could be natural materials, e.g. rocks or minerals, or manufactured, such as mixtures of different components, that may be biologically and/or organically doped.
What analogues for what purpose? Analogues with appropriate sample size and nature, as well as physical/chemical properties will be suited best for testing and training of sample handling procedures, and transport protocols. Training of science and curation teams also requires reference samples and standards. Long-term storage needs special witness plates and voucher specimens. Developing and testing sample preparation protocols need all analogue sample types.
A list of natural analogues considered a minimum to be available within the curation facility includes rocks and minerals but also gases and liquids. The latter two should be provided on demand if considered necessary.
Rocks identified are terrestrial igneous rocks (from basalt to tuff), sedimentary rocks, impact melt breccias, and meteorites, such as chondrites and achondrites. Minerals identified as necessary include major rock-forming minerals such as olivine and pyroxenes, metal (Fe-Ni kamacite and taenite), magnetite, haematite, calcite, dolomite, gypsum, anhydrite, perchlorates, sulphides, smectites, serpentine, silica polymorphs and ices. Masses should be on the order of 1 kg for miner-als and meteorites, and about 40 kg for terrestrial rocks.
Manufactured analogues need to simulate regolith and soil materials, various mixtures of soils (e.g. with perchlorate, ice), icy/dusty mixtures, biological and organic doped samples.
Each proposed analogue contains specific information which will be provided in the form of an spreadsheet, that was especially developed for this purpose (see below). It lists for the analogue: nature and provenance, a EURO-CARES code number, the target extraterrestrial body for which it is an analogue (specific mission, if relevant), the target body geological context, the curation facility storage, the analogue’s state of matter, a general geological description of the target including petrography, mineralogy, chemistry,etc.; physical properties, including density, hardness/compressive strength, porosity, tenacity; cleavage, fracture, electrical properties, magnetic pro-perites, thermal behaviour; health risks; location of the sample, if relevant; other information; associated data; history of the sample.
This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 640190