# Lithospace: an automated system for in situ petrographic thin section preparation on Mars

Frédéric Foucher, Nicolas Bost, Sylvain Janiec, Frances Westall, Pascal

Perron, Michel Bouquin, Aïcha Fonte, Nicole Le Breton, Michel Tagger,
Michel Viso, et al.

<figure><img src="image_1.png" /></figure>

► To cite this version:

Frédéric Foucher, Nicolas Bost, Sylvain Janiec, Frances Westall, Pascal Perron, et al. Lithospace: an automated system for in situ petrographic thin section preparation on Mars. European Planetary Science Congress 2018, Sep 2018, Berlin, Germany. insu-03352850

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# Lithospace: an automated system for in situ petrographic thin section preparation on Mars

Frédéric Foucher (1), Nicolas Bost (1), Sylvain Janiec (2), Frances Westall (1), Pascal Perron (3), Michel Bouquin (3), Aïcha Fonte (4,5), Nicole Le Breton (2), Michel Tagger (6), Michel Viso (7), Pascale Chazalnoël (8), Frédéric Courtade (8), Michel Villenave (8) and the students from Lycée Benjamin Franklin (3) and Polytech' Orléans (5)

(1) CNRS, CBM, Orléans, France, (2) ISTO, Université d'Orléans, France, (3) Lycée Benjamin Franklin, Orléans, France, (4) PRISME, Université d'Orléans, France, (5) Polytech' Orléans, France, (6) LPC2E, CNRS-Université d'Orléans, France, (7) CNES, Paris, France, (8) CNES, Toulouse, France, (frederic.foucher@cnrs.fr)

## Abstract

The aim of the LithoSpace project, supported by the CNES since 2014, is to work on the development of an automated system permitting preparation of petrographic thin sections on extraterrestrial bodies, in particular, on Mars.

## 1. Introduction

Optical microscopy in transmitted light is probably one of the most standard techniques in geology. It has been used for more than 150 years. Indeed, analyses of microscopic images of rocks and their characteristic mineralogy and textures are widely used in geological departments [1]. Observation in transmitted light permits identification of rocks having similar chemical and mineralogical compositions but different mineral organizations (basalt vs. gabbro for instance). Using polarized light, it permits identification of most of rock-forming minerals in thin section [2]. Observation in transmitted light is also essential for micropale-ontology since it is the only way to observe individual microfossils, if they are large enough 1, and to document the mineralogical and textural context in which the biosignatures occur. Nevertheless, optical observation in transmission has never been carried out on Mars. Indeed, although optical microscopes can be readily designed for space exploration, thin section preparation is not easy to do in situ. In particular, it requires several human manipulations that are difficult to automate.

The aim of the LithoSpace project, supported by the CNES since 2014, is to work on the development of an automated system permitting preparation of petrographic thin sections on extraterrestrial bodies, in particular, on Mars. Several studies and tests were conducted and most of the problems solved. The final

<figure><img src="image_3.png" /><figcaption>Figure 1: Pieces of rocks from (a) the Gunflint formation (-1,9 Ga) and (c) Svalbard, and (b,d) associated optical microscopy images in transmitted light. (d) Image in polarized-analyzed light.</figcaption></figure>

protocol follows the process from obtaining a standardized drill core to observation of a thin section in a fully automated way.

## 2. Proof-of-concept

The objective of the project is now to make a “proof-of-concept” model. Thus, a first numerical model of the system has been designed by students in fifth year at the engineering school Polytech', University of Orléans. With the help of students in BTS (two-year technical degree) “industrialization of mechanical products”, from the Benjamin Franklin high school of Orléans, the objective is now to make this model real. Finally, this study is a good way to raise student aware-
ness of space exploration by involving them directly at
the start of the project.

3. On the use of thin sections for in situ space exploration

*In situ* thin section preparation would be an impor-
tant improvement for the geological and astrobiologi-
cal exploration of the solar system, for Mars but also of
other planetary bodies. The proposed instrument could
incorporate new high resolution techniques, such as
Raman mapping or micro-LIBS as well as optical mi-
croscopic observation in transmitted light

**4. Summary and Conclusions**

The LithoSpace project permit us to propose a concept
for an automated system permitting preparation of pet-
rographic thin sections on extraterrestrial bodies. This
project appeared to be an excellent way to raise student
awareness of space science and technology. A group
of five students from the Lycée B. Franklin, helped by
their teachers, have started the development of a phys-
ical demonstration model to be presented during the
EPSC 2018 meeting.

Acknowledgements

We acknowledge the Polytech'Orléans students J. Li
and T. Platel and the Benjamin Franklin high school
students C. Navereau, Q. Truchot, R. Segret, S. De
Olivera and A. Tessier-Neilel for their work. We ac-
knowledge CNES for funding.

References

[1] MacKenzie, W.S. and Guilford, C.: Atlas of rock-
forming minerals in thin section, ed. Pearson Prentice
Hall, pp. 98, 1980.

[2] Michel-Lévy A., Interference color chart, 1888.