Mr SEAN MCMAHON
The University of Aberdeen
Department of Geology & Petroleum Geology,
School of Geosciences,
University of Aberdeen,
MESc Oxf (Hons) FRAS
2010-present: PhD candidate in Geology, University of Aberdeen
2006-2010: MEarthSci, St. Edmund Hall, University of Oxford
Fourth-year thesis: Deciphering a Palaeoproterozoic nutrient cycle: New evidence from phosphate in the 1.9-Ga Gunflint Formation, Canada
(supervised by Prof. Martin Brasier)
Third-year dissertation: How did Symbiosis Drive the Early Evolution of Eukaryotes?
Honours and awards
Summer 2013: NASA Planetary Biology Internship, NASA Ames Research Center, California
2013: Principal's Prize for Public Engagement with Research: Recognition of Special Achievement
2009: Palaeontological Association Undergraduate Prize for Best Third-Year Performance in Palaeontology.
Summer 2009: E.P. Abraham Internship, Oxford University Museum of Natural History (palaeontology curation)
Summer 2008: Nuffield Foundation Science Bursary Studentship: Animal Ancestors
My work applies geological perspectives and techniques to astrobiological problems ranging from the origin and distribution of life in the universe to the origin of methane in the martian atmosphere. I am particularly interested in microbes that live kilometres below the Earth’s land surface and seafloor: the possibility of such “deep biospheres” changes what it means for a planet to be habitable.
Geofluids in astrobiology
Deep biospheres and planetary habitability
Microbiology, especially methanogens
Origins of life
Palaeobiology, especially Precambrian micropalaeontology
Mars, Methane and Microbes: Identification of Methane-Rich Rocks and Their Potential to Support Life on Earth and Mars.
Funding: STFC (Aurora Programme, European Space Agency)
Supervisors: Professor John Parnell, Department of Geology & Petroleum Geology; Dr. Graeme Nicol, School of Biological Sciences
This research investigates the behaviour of methane in geological environments—especially in relation to micro-organisms—on Earth and Mars. Among the central questions are:
1. How effectively and by what processes do rocks and minerals—especially those that could be sampled on Mars—trap methane, and for how long do they retain it?
2. How can this methane be extracted and analysed, especially on Mars?
3. How do methane-producing and methane-oxidising micro-organisms on Earth relate to methane-bearing phases such as natural gas reservoirs, clathrate hydrates and fluid inclusions in minerals?
4. Which of these phases might be involved in an explanation for atmospheric methane on Mars?
5. What kinds of evidence do methanotrophs and methanogens leave in the geological record, and how could this evidence be located, recovered and analysed on Mars?
6. Could known methanogens and methanotrophs survive in a deep biosphere on Mars; in particular, what pressure and temperature conditions might such organisms endure and what are the biochemical and metabolic effects of these conditions?
Royal Astronomical Society (Fellow)
Astrobiological Society of Britain
Publications & Presentations
Peer-reviewed Journal Articles
1. Parnell, J., McMahon, S., Blamey, N. J. F., Hutchinson, I. B., Harris, L. V., Ingley, R., Edwards, H. G. M., Lynch, E. & Feely, M. (2014) Detection of reduced carbon in a basalt analogue for martian nakhlite: a signpost to a habitat on Mars. International Journal of Astrobiology (In press).
2. Price, M., Ramkissoon, N., McMahon, S., Miljkovic, K., Parnell, J., Wozniakiewicz, P., Kearsley, A., Blamey, N., Cole, M., & Burchell, M. (2014) Limits on methane release and generation via hypervelocity impact of Martian analog materials. International Journal of Astrobiology (In press).
3. McMahon, S., Parnell, J. (2013) Weighing the deep continental biosphere. FEMS Microbiology Ecology. In press.
4. McMahon, S., O'Malley-James, J., & Parnell, J. (2013) Circumstellar habitable zones for deep terrestrial biospheres. Planetary and Space Science 85: 312-318. dx.doi.org/10.1016/j.pss.2013.07.002
5. McMahon, S., Parnell, J., Ponicka, J., Hole, M., & Boyce, A. (2013) The habitability of vesicles in martian basalt. Astronomy & Geophysics 54: 1.17-1.21. dx.doi.org/10.1093/astrogeo/ats035
6. Brasier, M., Matthewman, R., McMahon, S., Kilburn, M., & Wacey, D. (2013) Pumice from the ~3,460 Ma Apex Basalt, Western Australia: a natural laboratory for the early biosphere. Precambrian Research 224: 1-10. dx.doi.org/10.1016/j.precamres.2012.09.008
7. McMahon, S., Parnell, J., & Blamey, N. J. F. (2013) Sampling methane in basalt on Earth and Mars. International Journal of Astrobiology 12: 113-122. dx.doi.org/10.1017/S1473550412000481
8. McMahon, S., Parnell, J., & Blamey, N. J. F. (2012). Sampling methane in hydrothermal minerals on Earth and Mars. International Journal of Astrobiology 11: 163-167. dx.doi.org/10.1017/S1473550412000067
9. Brasier, M.D., Matthewman, R., McMahon, S., & Wacey, D. (2011). Pumice as a Remarkable Substrate for the Origin of Life. Astrobiology 11(7): 725-735. doi:10.1089/ast.2010.0546.
Conference Papers and Presentations
(Presented) Parnell, J. & McMahon, S. (2012). Targeting the Deep Biosphere in the Search for Life. EANA 12th European Astrobiology Workshop, Stockholm, Sweden.
(Presented) McMahon, S., Parnell, J. & Blamey, N. J. F. (2012). Analysis of volatile fluids in basalt, a possible source of Martian methane. EANA 12th European Astrobiology Workshop, Stockholm, Sweden.
(Presented) McMahon, S. (2012).Plenary talk: Deep biospheres on Earth, Mars and beyond. ESA/ISGP Joint Life Sciences Meeting 2012, Aberdeen, UK.
(Presented) McMahon, S., Parnell, J. & Blamey, N. J. F. (2012). Analysis of volatile fluids in basalt, a possible source of Martian methane. Astrobiology Science Conference, Atlanta, Georgia, USA [awaiting online release].
McMahon, S., Parnell, J. & Blamey, N. J. F. (2012). Analysis of volatile fluids in basalt: a possible source of Martian methane. In Proc. Lunar and Planetary Science Conf. XLIII, abstract 1046.
McMahon, S., Parnell, J., Burchell, M. & Blamey, N. J. F. (2012). Methane retention by rocks following simulated meteorite impacts: implications for Mars. In Proc. Lunar and Planetary Science Conf. XLIII, abstract 1040.
(Presented) McMahon, S. (2011) Is Earth's Biosphere Exceptionally Surficial? Royal Astronomical Society Specialist Discussion Meeting ("Is the Earth Special?"), December 9th 2011.
(Co-presented) Parnell, J., McMahon, S., Blamey, N. (2011) Identification of methane-rich rocks and their potential to support life, on Earth and Mars. Royal Astronomical Society Specialist Discussion Meeting ("UK Participation in Aurora"), January 14th 2011.
Brasier, M.D., Matthewman, R., McMahon, S., & Wacey, D. (2011). Pumice as a remarkable substrate for the origin of life. EGU General Assembly 2011. In Geophysical Research Abstracts Vol. 13, abstract EGU2011-3929
Brasier, M.D., Battison, L., McMahon, S., Wacey, D. (2010). Opening the phosphate window onto early life—the 1900 Ma Gunflint Chert. In 20th Australian Earth Sciences Convention (AESC), p. 89.
I am enthusiastic about sharing science with everybody. I am now registered as a STEM Ambassador.
Volunteering & Events:
2013. Speaker, Meet the Expert/Stargazing Live, Satrosphere, Aberdeen: "Life on Mars: Past, present and future."
2012. Speaker, British Science Festival session: "Is life on Earth exceptionally shallow?"
2012. Presenter, Café Cosmos evening event, Aberdeen College Planetarium: "Is Life on Earth Exceptionally Shallow?"
2011. Speaker, Techfest Highland Schools Tour: "From Cells to Cellphones". Five schools in the Scottish Highlands.
Popular Science Writing
2010–present. Au Science Magazine, University of Aberdeen.
What's Mars Hiding? — Feature article about life on Mars (Issue 1)
Mind the Gap — A discussion of art and science (Issue 1)
Philosophy? Naturally — History of the philosophy of science (Issue 2)
Why Science? — An argument that science is interesting! (Blog)
Aberdeen's Nobel Pride — An account of Aberdeen's five Nobel Prize-winning scientists (Issue 2)
Carnival of the animals (with Scott Byrne) — Feature article about the incredible Aberdeen Bestiary (www.abdn.ac.uk/bestiary)
2012. Oxonian Review — 2011: The Year in Science (Blog)
Scientific Illustration, Layout & Design
2010–2012. Creative Editor, Au Science Magazine Issues 1–5, University of Aberdeen.
2009–present. Designer, Science and Celebrities annual leaflet, Sense About Science.
2008–2009. Creative Director, Bang! Science Magazine, University of Oxford.
update | about Staff Pages