An astrobiological study of an alkaline-saline hydrothermal environment, relevant to understanding the habitability of Mars A thesis submitted for the Degree of Doctor of Philosophy By Lottie Elizabeth Davis Department of Earth Sciences University College London March 2012 1 I, Lottie Elizabeth Davis confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. 2 Declaration Abstract The on going exploration of planets such as Mars is producing a wealth of data which is being used to shape a better understanding of potentially habitable environments beyond the Earth. On Mars, the relatively recent identification of minerals which indicate the presence of neutral/alkaline aqueous activity has increased the number of potentially habitable environments which require characterisation and exploration. The study of terrestrial analogue environments enables us to develop a better understanding of where life can exist, what types of organisms can exist and what evidence of that life may be preserved. The study of analogue environments is necessary not only in relation to the possibility of identifying extinct/extant indigenous life on Mars, but also for understanding the potential for contamination. As well as gaining an insight into the habitability of an environment, it is also essential to understand how to identify such environments using the instruments available to missions to Mars. It is important to be aware of instrument limitations to ensure that evidence of a particular environment is not overlooked. This work focuses upon studying the bacterial and archaeal diversity of Lake Magadi, a hypersaline and alkaline soda lake, and its associated hydrothermal springs. Culture dependent and culture independent analytical methods have been used and have led to the identification of potentially novel isolates. In addition, the effects of simulated Martian conditions such as desiccation and UVC radiation upon single strains isolated from this environment, and the effects upon a complex soil community have been assessed. Results have also provided an indication of what issues may arise with identifying minerals associated with these environments using the equipment such as the ExoMars PanCam. It is hoped that this work has contributed to our understanding of the possible habitability of Mars. 3 Abstract Acknowledgements There are many people I want to thank for their help, advice and guidance over the past three and a half years. Firstly want to thank my supervisors Dr. Ian Crawford and Prof. John Ward for their constant enthusiasm, guidance and support throughout, and Dr. Adrian Jones and Dr Graham Shields-Zhou for their assistance and help during my PhD. I cannot thank Dr. Claire Cousins enough for all her advice and patience right from the start, and for sitting with me in the middle of nowhere in the cold, rain and hail to teach me how to sample in the field. I must also thank Dr. Stephanie Hunter, Dr. Markus Gershater and Dr. Lewis Dartnell, for their invaluable guidance and assistance in the laboratory. This work is almost entirely centred upon samples collected from Kenya, therefore I also want to thank Dr. Abigail Church, the Kenyan field work team, Ian Patmore and Professor Eric Odada, without whom the field work in Kenya could not have been possible. I also want to thank Dr. Andrew Griffiths who allowed me to test the PanCam instrument, Matt Gunn for his help with analytical instruments, and the stranger in the raman laboratory who brought me a cup of tea when everything seemed to be going wrong. I must also thank Dr. Manish Patel for allowing me to use the Mars chamber facilities and Dr Terry McGenity and Mr tony Osbourne for their help with water analyses. I want to give a big thank you to my two offices, firstly to Ceri, Claire, Josh, Shoshana, Pete, Dom, Helen and everyone in the planetary office (at some point) for numerous entertaining and often somewhat bizarre lunchtime conversations and for the all-important tea breaks and cake time. I also want to say a massive thank you to the biology office, to Oriana, Steph, Pedro, John (Mr), Markus, Lewis, Julio & Vishal for making the office and laboratory such an entertaining, friendly and fun environment, and for the much needed light relief during tea breaks and evenings out. I also want to thank the support staff at UCL, whose upbeat good mornings made the early starts in the laboratory more bearable. Also thank want to thank Esme, for your help and advice, and all the Biggin Hill Billies (and their partners) for listening to me gabble on about my work. I am also so grateful to Laura, for being there throughout it all, field work, transfer reports, and thesis writing, you have been fantastic friend and for that I thank you. I must thank my family, Mum, Dad, George, Gran, Grandad, Peter, Sheila, Jane, Malcolm and Lily and all the Davis’, the Wynne-Jones’, Howses and Hobdays, for the help and confidence that they have always had in me. Without your support, this would not have been possible. Finally, I must thank my boys, Bertie and my wonderful Mikey. Mike, I could not have done this without you, your belief in me, your patience and support, your dinners and the constant supply of yet more teas. I cannot thank you enough for putting up with my stress and endless yabbering on. I just hope I can be as much of a rock for you, as you have been for me. 4 Acknowledgements Contents Abstract .................................................................................................................................... 3 Acknowledgements .................................................................................................................. 4 List of abbreviations ........................................................................................................... 16 List of Figures ..................................................................................................................... 17 List of Tables ...................................................................................................................... 30 A study of alkaline-saline environments relevant to understanding the habitability of Mars ... 33 1.1. Alkaline environments and the origin of Life ................................................................ 34 1.2. Terrestrial saline alkaline environments ...................................................................... 35 1.3. Saline-alkaline lakes of the East African Rift Valley .................................................... 36 1.4. Hydrochemistry and geology of Lake Magadi ............................................................. 38 1.5. Identification of alkaline-saline deposits in the geological record ................................ 40 1.6. Microbiology of alkaline and saline environments ....................................................... 41 1.6.1. Environmental microbiology ..................................................................................... 41 1.6.2. Extremophile and extremotolerantorgansisms ......................................................... 43 1.6.3. Adaptation to extreme environments and stress factors ........................................... 45 1.6.3.1. High NaCl concentration ....................................................................................... 45 1.6.3.2. Alkaline pH ............................................................................................................ 45 1.6.3.3. Desiccation ............................................................................................................ 46 1.6.3.4. Ultraviolet-245nm (UV-C) radiation ....................................................................... 47 1.6.3.5. Ionizing radiation (IR) ............................................................................................ 48 1.6.3.6. Resistance to Desiccation, UV-C and Ionizing radiation ....................................... 49 1.7. Alkaline-saline environments as extraterrestrial analogues ......................................... 49 1.8. Relevance of alkaline-saline environments to planetary bodies within our solar system ........................................................................................................................................... 50 1.8.1. Europa ...................................................................................................................... 50 1.8.2. Enceladus................................................................................................................. 51 1.8.3. Mars ......................................................................................................................... 52 1.8.3.1. Exploring the surface of Mars ................................................................................ 52 1.8.3.1.1. ExoMars PanCam instrument ............................................................................. 56 1.8.3.2. Environments on present day Mars ....................................................................... 57 1.8.3.3. Environments on past Mars ................................................................................... 58 1.8.3.4. Hydrated minerals on Mars ................................................................................... 61 1.8.3.4.1. Phyllosilicates ..................................................................................................... 61 1.8.3.4.2. Carbonates ........................................................................................................