Raman spectroscopy is a technique employed to identify mineral phases produced by water-related processes.[3][4][5] RLS will help to identify organic compounds and search for microbial life by identifying the mineral products and indicators of biologic activities. RLS will provide geological and mineralogical context information that will be scientifically cross-correlated with that obtained by other instruments.[6]
Raman spectroscopy is sensitive to the composition and structure of any organic compound, making it a powerful tool for the definitive identification and characterisation of biomarkers, and providing direct information of potential biosignatures of past microbial life on Mars.[3] This instrument will also provide general mineralogical information for igneous, metamorphous, and sedimentary processes.[3]
RST will also correlate its spectral information with other spectroscopic and imaging instruments such as the Infrared Spectrometer and MicrOmega-IR.[3] This will be the first Raman analyser to be deployed for a planetary exploration.[6] The first version for the rover was presented by Fernando Rull-Perez and Sylvestre Maurice in 2003.[6] The RLS is being developed by a European consortium integrated by Spanish, French, German and UK partners.[6] The Principal Investigator is Fernando Rull-Perez, from Spanish Astrobiology Center.[3] The co-investigator is from Observatoire Midi-Pyrénées (LAOMP), France.[8]
The three major components are the Spectrometer Unit, the Control and Excitation Unit (includes the power converters), and Optical head.[9]
Principle and operation
The RLS instrument provides a structural fingerprint by which molecules can be identified. It is used to analyse the vibrational modes of a substance either in the solid, liquid or gas state.[6] The technique relies on Raman scattering of a photon by molecules which are excited to higher vibrational or rotational energy levels. In more detail, it will collect and analyse the scattered light emitted by a laser on a crushed Mars rock sample; the spectrum observed (number of peaks, position and relative intensities) is determined by the molecular structure and composition of a compound, enabling the identification and characterisation of the compounds in the sample.[3]
Some advantages of RLS over other analysers are that it is nondestructive, analysis is completed in a fraction of a second, and the spectral bands provide definitive composition of the material.[6] RLS measurements will be conducted on the resulting crushed sample powder and it will be a useful tool for flagging the presence of organic molecules for further biomarker search by the MOMA analyser.[citation needed]
The processor board carries out several key functions for the Raman spectrometer control, spectral operation, data storage, and communications with the rover. The complete instrument has a mass of 2.4 kg (5.29 lb) and consumes about 30 W while operating.[3][6][7]
^ abcdefghThe Raman Laser Spectrometer for the ExoMars Rover Mission to Mars. Fernando Rull, Sylvestre Maurice, Ian Hutchinson, Andoni Moral, Carlos Perez, Carlos Diaz, Maria Colombo, Tomas Belenguer, Guillermo Lopez-Reyes, Antonio Sansano, Olivier Forni, Yann Parot, Nicolas Striebig, Simon Woodward, Chris Howe, Nicolau Tarcea, Pablo Rodriguez, Laura Seoane, Amaia Santiago, Jose A. Rodriguez-Prieto, Jesús Medina, Paloma Gallego, Rosario Canchal, Pilar Santamaría, Gonzalo Ramos, Jorge L. Vago, and on behalf of the RLS Team. Astrobiology, 1 July 2017, 17(6-7), pages 627-654. doi:10.1089/ast.2016.1567
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