Metals for Life in Earth & Planetary Sciences
Résumé
Metals are pre-requisites for life, fingerprints of life and tracers of metabolic processes of biomineralisation in living organisms. To study metals at macromolecular interaction scales requires state of the art analytical capabilities down to trace element levels and nanometer spatial resolutions. Fortunately, in the last decade, highly sensitive X-ray probes have been developed at worldwide 3rd generation synchrotron facilities. To date, a limited number of these highly specific nanoimaging probes have been deployed, and the ESRF ID16A/B and ID21 ones are among the leaders. X-rays are non (or least) destructive, noninvasive, penetrative and highly sensitive probes of solid samples and metals are their ideal targets. X-ray fluorescence has reached few tens of nm resolutions and a world record for absolute mass of e.g. 50 zg for Fe, which
can be recognized as only about 600 atoms. Over the past decade, we have developed a multi-analyses methodology of nanoimaging mid-Z elements in low-Z matrices as a direct application to Life and/or Planetary Sciences of trace metals in biological matrices or in C/Si-based ones.
X-ray fluorescence and absorption spectroscopies, deployed at the few nanometer scales, are sensitive probes but they require a re-assessment of the analytical requirements previously established at the few micron levels [1]. We will present some specific analytical developments and methodologies optimized for such applications. They are centered onto absolute quantification of metals using both the Fundamental Parameter Approximation and reference materials, after spectra analysis using the PyMCA package [2] coupled to Monte-Carlo simulations of sample compositions [3] and geometries, prerequisites for 2D/3D elemental imaging. Examples based on metal detection were applied to either environmental key organisms such as foraminifers or coccolithofores [4, 5] but also to the oldest living organisms traced
back to life's origins on Earth [1]. Finally, our search for life being also aimed at planetary and astronomical scales on exoplanets, we will present our patented methodology and sample holder [6] for Quarantine Extraterrestrial Sample Analyses (QESA) for the upcoming Returned Sample Missions from Mars and asteroids [7].
[1] – L. Lemelle, A. Simionovici et al., Trends Anal. Chem. 91, 104–111, 2017.
[2] – Solé, V.A., Papillon, et al., Spectrochim. Acta B, 62, 63-68, 2006.
[3] – T. Schoonjans, L. Vincze, V.A. Sol_e, et al., Spectrochim. Acta B 70, 10-23, 2012.
[4] – L. Lemelle, A. Bartolini, A. Simionovici, et al., Nature Comm., (in review) 2019.
[5] – B. Suchéras-Marx, F. Giraud, A. Simionovici et al., Geobiology 14, 390-403, 2016.
[6] – A. Simionovici and CNES, European Patent Office # EP2411791A1, 2010.
[7] – A. Simionovici, L Lemelle et al., Proc. of the EAS Annual Meeting, EWASS, 2019
