A NEW HABITABILITY ASSESSMENT AND ORGANIC MATTER DETECTION INSTRUMENT FOR MARS PETER RORY GORDON Department of Earth Science and Engineering Imperial College London A thesis submitted for the degree of Doctor of Philosophy The copyright of this thesis rests with the author and is made available under a Creative Commons Attribution Non-Commercial No Derivatives licence. Researchers are free to copy, distribute or transmit the thesis on the condition that they attribute it, that they do not use it for commercial purposes and that they do not alter, transform or build upon it. For any reuse or redistribution, researchers must make clear to others the licence terms of this work. All original data and results presented in this thesis are the outcome of my own work; any work by others has been appropriately credited. All passages of text have been authored by myself with the editorial assistance of my supervisor. Peter Rory Gordon Supervisor: Prof. Mark Sephton Mars Sample Return is the next major step in the search for life beyond Earth. Mineralogical studies have revealed a wetter, more dynamic Mars than previously considered; the past environments of Mars could have hosted life and the search for its remains is a major scientific preoccupation. The return to Earth of the very best samples requires an effective prioritization and selection process, thus there is a requirement for a triage instrument which examines mineral phases in situ to determine the habitability potential of a region and to detect important biosignatures contained in any rock. This thesis demonstrates the viability of a pyrolysis-Fourier transform infrared spectroscopy (FTIR) instrument to fulfil these mission requirements. Thermal decomposition techniques have long been used on Mars to analyse solid samples, and FTIR instruments have been successfully deployed on the Martian surface. The combination of the two presents a resource efficient and robust analytical solution. Investigations were conducted using pyrolysis-FTIR to show how habitability and the biosignature preservation potential of rocks can be assessed through the release of key gases, namely carbon dioxide, water and sulfur dioxide. The sensitivity limits for detecting organic matter and the effects of different mineral matrices on the organic compound signal were also investigated though measurement of methane and larger hydrocarbon compounds. Finally a field study was conducted using samples collected from a sulfate stream ecosystem which represents an analogue for the Hesperian of Mars. The investigations have shown that pyrolysis-FTIR, through utilisation of different temperature modes and the qualitative and quantitative feedback of resulting spectra, provides adequate information to determine mineral phases relating to habitability. Pyrolysis-FTIR detects organic compounds present in quantities as low as tens of parts-per-million. Sulphates and chlorinated mineral phases diminish organic compound signals, but combustion products offer another avenue for detection. The field study demonstrated that a phased pyrolysis-FTIR protocol will select the most valuable samples. This thesis includes recommendations for the progress of pyrolysis-FTIR to the next design iteration. 3 I first must recognise the privilege that has been afforded to me by Imperial College London and the Science and Technology Facilities Council. These past four years have been an arena for me to develop personally as well as academically; this has only been a material opportunity through the investment and support provided by these institutions. Most of this development has been facilitated by the staff and colleagues throughout the college who have shared this experience with me (to whom I will find more appropriate displays of gratitude than a few lines in a thesis). Regarding the project, it is appropriate to give special recognition to Dr. Richard Court for laying the pyrolysis-FTIR groundwork and providing guidance and assistance, Dr. Jon Watson and Dr. Wren Montgomery for general lab assistance and administration, and Dr. James Lewis for his generosity in collaboration and ever-so-dependable Mars expertise. Dr. Caroline Smith of the Natural History Museum and Dr. Karen Olsson-Francis of the Open University are thanked for hosting me on sub-project work. Of course my successes would not have been possible without the love and support of my family and friends. I am truly humbled by my parent’s dedication and sacrifice and thank them dearly for their support. However, the lion’s share of gratitude is reserved for my supervisor, Prof. Mark Sephton. The academic and professional assistance and wisdom he has provided surpassed all expectations, only to be exalted by displays of personal support. His consolidation of experience, insight and academic prowess is a significant asset to this department, thus my blessings have been well and truly counted having landed myself as one of his students. Considering some of the challenges presented it’s not far-fetched to envisage less desirable outcomes had it not been for the affable nature and patience so defining of Mark’s character, and for that I will be eternally indebted. It is my sincere wish that this work brings returns that are well in excess of his investment. 4 Published works • Mark A. Sephton, Richard W. Court, James M. Lewis, Miriam C. Wright, Peter R. Gordon, Selecting samples for Mars sample return: Triage by pyrolysis–FTIR, Planetary and Space Science , Volume 78, April 2013, Pages 45-51, ISSN 0032-0633, http://dx.doi.org/10.1016/j.pss.2013.01.003. • Peter R. Gordon, Mark A. Sephton, Rapid habitability assessment of Mars samples by pyrolysis- FTIR, Planetary and Space Science , Volume 121, February 2016, Pages 60-75, ISSN 0032-0633, http://dx.doi.org/10.1016/j.pss.2015.11.019. Accepted for publication • Peter R. Gordon, Mark A. Sephton, Organic matter detection on Mars by pyrolysis-FTIR: an analysis of sensitivity and mineral matrix effects, Astrobiology. In preparation • Peter R. Gordon, Mark A. Sephton, Pyrolysis-FTIR survey of an acid stream ecosystem and its implications for sample triage during Mars Sample Return. 5 Abstract ............................................................................................................................................. 3 Acknowledgements................................................................................................................................... 4 Publications by the author ........................................................................................................................ 5 Published works ................................................................................................................................... 5 Accepted for publication ...................................................................................................................... 5 In preparation ...................................................................................................................................... 5 Contents ............................................................................................................................................. 6 List of figures ......................................................................................................................................... 11 List of tables ........................................................................................................................................... 14 List of abbreviations ............................................................................................................................... 17 Chapter 1 Review of sample return missions, life on Mars and instrument development ..................... 19 1.1 Introduction to thesis ............................................................................................................. 20 1.2 Sample return ......................................................................................................................... 21 1.3 Pyrolysis-FTIR ....................................................................................................................... 24 1.3.1 FTIR in a triage application ........................................................................................... 24 1.3.2 Pyrolysis in a triage application ....................................................................................... 25 1.3.2.1 Thermal decomposition of minerals ........................................................................... 25 1.3.2.2 Extraction and thermal fission of organic matter ........................................................ 26 1.3.3 Pyrolysis-FTIR as part of Mars Sample Return ............................................................... 26 1.4 Life on Mars ........................................................................................................................... 29 1.4.1 Mineralogical indicators of habitability ........................................................................... 29 1.4.2 Indicators of life ............................................................................................................. 31 1.4.2.1 Biosignatures in the atmosphere ................................................................................. 34 1.5 Instrument Design Process ..................................................................................................... 35 1.5.1 Instrument performance thresholds ...............................................................................