Friends of the RAS (only) lecture: False biosignatures on Mars?

Artificially created carbon-sulphur biomorphs under a microscope
Artificially created carbon-sulphur biomorphs under a microscope
Julie Cosmidis (University of Oxford)
Start Date
End Date

This lecture will be a hybrid event meaning that Friends of the RAS will be able to attend in-person or online via Zoom. A ticket link will be emailed the Friends in due course.

You must book a ticket in advance to attend this lecture.


The search for life on Mars is not easy. Previous detections turned out to be mistaken: scientists were misled by objects, patterns and substances that resembled life but were not really biological in origin. In this talk, I will discuss the history of false biosignatures on Mars and analyse what went wrong. I will then discuss some of the remarkably lifelike objects, patterns and substances that could have formed on (early) Mars by purely geological, chemical and physical processes of self-organisation. All of these phenomena are interesting and beautiful in their own right, many of them can only occur in habitable environments, and some of them may have been involved in the origin of life on Earth. Understanding them may be critical for verifying any future detection of life on Mars.


Sean McMahon is an astrobiologist and co-director of the UK Centre for Astrobiology at the University of Edinburgh. His interests span the chemistry of fossilisation, the identification of fossil bacteria, the origin and early evolution of life, the search for life on Mars, and the problem of false positives in astrobiology. He has published more than fifty papers on these and related topics, combining fieldwork (on Earth!), laboratory experiments, and the use of high-resolution imaging and analysis techniques. Sean was educated at Oxford and then Aberdeen, where his PhD focused on possible sources of methane in the martian atmosphere. He undertook postdoctoral work at Yale University focusing on the chemistry of organic fossil preservation and its implications for the selection of landing sites and samples for Mars missions. He returned to Scotland in 2017 and now leads a research group in the School of Physics and Astronomy and the School of GeoSciences at Edinburgh.