J. Phys. IV France 104 (2003) 377
X-ray imaging techniques and exobiologyL. Lemelle1, A. Simionovici1, 2, J. Susini3, Ph. Oger1, M. Chukalina4, C. Rau2, B. Golosio2 and Ph. Gillet1
1 Laboratoire de Sciences de la Terre de l'ENS Lyon, 46 allée d'Italie, 69007 Lyon, France
2 ID22 Group, European Synchrotron Radiation Facility, ESRF, 6 rue G. Horowitz, BP. 220, 38043 Grenoble cedex, France
3 ID21 Group, European Synchrotron Radiation Facility, ESRF, 6 rue G. Horowitz, BP. 220, 38043 Grenoble cedex, France
4 Institute of Microelectronics Technology RAS, 142432 Chernogolovka, Russia
X-ray imaging techniques at the best spatial resolution and using synchrotron facilities are put forth as powerful techniques for the search of small life forms in extraterrestrial rocks under quarantine conditions. Absorption and fluorescence X-ray microtomographies on sub-millimeter silicate assemblages inside a container reveal the mineralogical microenvironments were life should be looked for in priority. Limitations with respect to bacterial detection are due to the difficulties to obtain information about light elements ( ), major constituents of biological and silicate samples. The X-ray signature of a "present" bacteria on a silicate surface was defined by X-ray mapping, out of a container, as coincident micrometer and oval zones having strong P and S fluorescence lines (S-fluorescence being slightly lower than P-fluorescence) and an amino-linked sulfur redox speciation. The detection of a single cell along with new procedures to calculate tomographic views will allow considerable improvements of 3D detection of life by X-ray techniques.
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