Liam Harris - Presenter Profile

Lasers on Mars: Raman Spectroscopy of Reduced Carbon in Preparation for the ExoMars Rover Mission

In this article, Liam Harris describes his research into how we might detect signs of past or present life on Mars.

About My Research

MarsI study an analytical technique called Raman spectroscopy, which is used to identify and characterise unknown materials.

It works by shining a coloured laser on a material (I usually use a green laser, but different colours have different advantages); some energy from the laser is absorbed, causing it to change colour and become redder. This colour change is specific to each material, acting like a fingerprint enabling us to identify it. Raman spectroscopy is routinely used to identify paints in works of art, suspicious liquids in airports and prescription drugs manufactured by pharmaceutical companies, however it has not yet been used on another planet.

In 2018 the European and Russian Space Agencies will launch the ExoMars rover, a mission to Mars with a goal to look for signs of past or present life. It will be equipped with a 2m drill to acquire samples from below the martian surface and numerous scientific instruments to analyse them, including the first Raman spectrometer to be sent into space (a spectrometer is a device used to do spectroscopy). My PhD involves determining the optimum design for the spectrometer and the best way to operate it and analyse the data it acquires, all for the highest chance of detecting signs of life.

To make recommendations about spectrometer design and operation it is necessary to test prototypes in the lab. Through collaboration with geology and geochemistry experts and also my own field work, I seek natural rock samples from Earth that have similarities to particular aspects of Mars. These samples, also known as analogues, could contain minerals that we know are abundant on Mars, have undergone chemical and geological processes that we believe occur on Mars, or contain traces of life that we expect to find on Mars if indeed life has ever existed there. Such traces of life might include chemical compounds produced by living organisms, or changes within rock that indicate the influence of microbial life.

Once these analogue samples have been identified, I study them in the lab using several Raman spectrometers, under different conditions (for example some of each sample is crushed and the powder studied) and using different analysis techniques. This allows me to determine what might be learned about a sample using Raman spectroscopy. It also enables me to make recommendations about the design of current and future spectrometers for space missions, how they should be operated for certain sample types and the most appropriate methods of analysis.

My Research Findings

I have studied a broad range of analogue samples to build up a detailed picture of what the Raman spectrometer will “see” when the ExoMars rover reaches Mars. Although these samples include many different mineral types, I have a particular interest in the detection and characterisation of carbon deposits in rock, so many of the samples I have used are especially rich in carbon.

When living organisms die, various carbon-based compounds remain in the environment, become buried and are subsequently processed by heat and pressure. This produces carbon that persists in rock for hundreds of millions of years and therefore if there has ever been life on Mars, the ExoMars rover could detect such carbon deposits. If it succeeds in its mission to detect signs of life, even long extinct life, it would be the first detection of life away from Earth. This would be exciting and highly significant, as it would provide a comparison with life here on Earth, allowing us to really begin to understand what life is and how it starts. A second example of life in the Solar System would also give us a better idea of how common life might be throughout the Universe.

Unfortunately not all carbon is of biological origin. It is abundant in meteorites, so any impacts could deposit carbon on a planet. It is also produced via volcanic activity and Mars was once volcanically active, even if it is a cool world today. Raman spectroscopy is unable to distinguish between carbon of biological and non-biological origins, however detection of even non-biological carbon on another planet would be extremely important. Any environment rich in carbon would be an ideal habitat for microbial life, as organisms require a source of carbon to produce chemicals necessary for survival. This means that carbon could act as a signpost, pointing to an area that should be investigated more thoroughly with other analytical techniques that take longer to produce results than Raman, but might provide greater detail.

I have shown that the Raman spectrometer onboard the ExoMars rover will indeed be capable of detecting carbon, even at very low concentrations (I am currently working to establish the lowest concentration that could be detected). The spectrometer will be capable of more than just detection however, as with careful analysis it is also possible to determine how thermally mature the carbon is. Put simply, thermal maturity describes how deep the carbon was buried, how hot it got and how old it is. This will be a particularly valuable technique on another planet such as Mars, because it allows samples with the greatest chance of harbouring life to be identified for analysis by other techniques. It also enables us to spot multiple sources of carbon in one sample, which might aid in finding carbon of biological origin. Finally, this work has allowed me to make recommendations to the planetary exploration community about the best spectrometer design for detecting carbon on another planet, including laser colour and power and the kind of camera to use, which I hope will influence the design of current and future spectrometers.

In the future my research will continue to explore what more Raman spectroscopy can tell us about carbon, as well as other signs of life that the ExoMars rover might encounter on Mars, and the optimum spectrometer designs for detecting them.

About Liam Harris

Liam Harris is a PhD Student at the University of Leicester (2015)Liam Harris is a research student working towards completion of his doctoral degree in the Department of Physics and Astronomy. Liam is supervised by Dr Ian Hutchinson and Dr Richard Ingley.

Liam will present his work at the Festival of Postgraduate Research 6 July 2015 - see Liam's Festival poster.

The Festival is open to all members of the University community and the public - book your place here.

Contact Liam

Department of Physics and Astronomy

University of Leicester

University Road

LEICESTER

LE1 7RH

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