Full title Effect of grain size distribution on Raman analyses and the consequences for in situ planetary missions Short title Effect of grain size distribution on Raman analyses Authors and affiliations

Raman spectroscopy can be used for analysing both mineral and organic phases, thus allowing characterisation of the microbial-scale geological context as well as the search for possible traces of life. This method is therefore very useful for in situ planetary exploration missions. Compared to the myriad of sample preparation techniques available in terrestrial laboratories, the possibilities for sample preparation during in situ missions on other planetary bodies is extremely limited and is generally restricted to abrasion of rock surfaces or crushing of the target samples. While certain techniques need samples to be prepared in powder form, such as X-Ray Diffraction, this kind of preparation is not particularly suitable for optical microscopy and/or Raman spectroscopy. In this contribution, we examine the effects of powdering rock and mineral samples on optical observations and Raman analyses. We used a commercial Raman spectrometer, as well as a Raman Laser Spectrometer (RLS) that simulates the instrument being developed for the future ExoMars 2018 mission. The in su -0 08 19 72 2, v er si on 1 19 A ug 2 01 3 Author manuscript, published in "Journal of Raman Spectroscopy 44, 6 (2013) 916-925" DOI : 10.1002/jrs.4307