Raman Laser Spectrometer

Raman Laser Spectrometer (RLS) is a miniature Raman spectrometer that is part of the science payload on board the European Space Agency's Rosalind Franklin rover,[3] tasked to search for biosignatures and biomarkers on Mars. The rover is planned to be launched in August–October 2022 and land on Mars in spring 2023.[2]

Raman Laser Spectrometer

Operator	European Space Agency
Manufacturer	(INTA)
Instrument type	Raman spectrometer
Function	mineralogical composition
Mission duration	≥ 7 months[1]
Website	ExoMars Rover Instrument Suite
Host spacecraft
Spacecraft	Rosalind Franklin rover
Operator	European Space Agency
Launch date	August–October 2022[2]
Rocket	Proton-M/Briz-M
Launch site	Baikonur

Raman spectroscopy is a very useful technique employed to identify mineral phases produced by water-related processes.[4][5][6] 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.[7]

Overview

RLS	Parameter/units[8]
Type	Raman spectrometer
Mass	2.4 kg
Power consumption	20W to 30 W
Laser wavelength	532 nm
Irradiance on sample	0.4 - 8 kW/cm^2
Spectral range	150-3800/cm^−1
Spectral resolution	6 to 8/cm
Spot size	50 μm

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.[4] This instrument will also provide general mineralogical information for igneous, metamorphous, and sedimentary processes.[4]

RST will also correlate its spectral information with other spectroscopic and imaging instruments such as the Infrared Spectrometer and MicrOmega-IR.[4] This will be the first Raman analyser to be deployed for a planetary exploration.[7] The first version for the rover was presented by Fernando Rull-Perez and Sylvestre Maurice in 2003.[7] The RLS is being developed by a European consortium integrated by Spanish, French, German and UK partners.[7] The Principal Investigator is Fernando Rull-Perez, from Spanish Astrobiology Center.[4] The co-investigator is from Observatoire Midi-Pyrénées (LAOMP), France.[9]

The three major components are the Spectrometer Unit, the Control and Excitation Unit (includes the power converters), and Optical head.[10]

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.[7] 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.[4]

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.[7] 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.

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.[4][7][8]

Objectives

The goal of RLS is to seek signs of past life on Mars (biosignatures and biomarkers) by analysing drilled samples acquired from 2  meters below the Martian surface by the Rosalind Franklin rover core drill. The science objectives of RLS are:[7]

1. Identify organic compounds and search for life.[11]
2. Identify mineral products and indicators of biologic activity.[11]
3. Characterize mineral phases produced by water-related processes.
4. Characterize igneous minerals and their alteration products.
5. Characterize the water/geochemical environment as a function of depth in the shallow subsurface.

See also

• Astrobiology
• Life on Mars

References

1. Vago, Jorge L.; et al. (July 2017). "Habitability on Early Mars and the Search for Biosignatures with the ExoMars Rover". Astrobiology. 17 (6–7): 471–510. Bibcode:2017AsBio..17..471V. doi:10.1089/ast.2016.1533. PMC 5685153. PMID 31067287.
2. "N° 6–2020: ExoMars to take off for the Red Planet in 2022" (Press release). ESA. 12 March 2020. Retrieved 12 March 2020.
3. Howell, Elizabeth (July 24, 2018). "ExoMars: Searching for Life on Mars". Space.com. Retrieved March 13, 2020.
4. "The ExoMars Rover Instrument Suite: RLS - Raman Spectrometer". European Space Agency. 3 April 2013.
5. Popp, J.; Schmitt, M. (2006). "Raman spectroscopy breaking terrestrial barriers!". Journal of Raman Spectroscopy. 35 (6): 18–21. Bibcode:2004JRSp...35..429P. doi:10.1002/jrs.1198.
6. Rull Pérez, Fernando; Martinez-Frias, Jesus (2006). "Raman spectroscopy goes to Mars" (PDF). Spectroscopy Europe. 18 (1): 18–21.
7. The 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
8. Raman Laser pectrometer for 2020 ExoMars Mission. Engineering and qualification model capabilities and future activities. (PDF). A. G. Morala, F. Rull, S. Maurice, I. Hutchinson, C.P. Canora, L. Seoane, R. Canchal, P. Gallego, G. Ramos, J.A.R. Prieto, A. Santiago, P. Santamaría, M. Colombo, T. Belenguer, G. López, C. Quintana, J. Zafra, A. Berrocal, C. Pintor, J. Cabrero, J. Saiz. 49th Lunar and Planetary Science Conference 2018. LPI Contrib. No. 2083.
9. "The ExoMars Rover Instrument Suite". exploration.esa.int. Retrieved 2018-07-22.
11. The search for signatures of early life on Mars: Raman spectroscopy and the Exomars mission. Howell G.M. Edwards, Ian B. Hutchinson, Richard Ingley, Nick R. Waltham, Sarah Beardsley, Shaun Dowson, and Simon Woodward. Spectroscopy Europe.