Deep Biospheres on Earth and Mars


D-BIOME (Deep BIOspheres on Mars and Earth) is the name of my current research project at the University of Edinburgh. This work is supported by the European Commission under a Marie Skłodowska-Curie Individual Fellowship as part of the Horizon 2020 programme of the European Union (the content of this website reflects only my own views and not those of the European Commission or the University).

What is this research about?

The Earth’s crust is porous, full of water, and teeming with tiny organisms like bacteria, which together belong to a vast hidden ecosystem referred to as the “deep biosphere”, which reaches miles downwards. This deep biosphere is as old as life itself (or very nearly), but we know almost nothing about its past. The deep biosphere is eagerly studied by microbiologists, but its fossil record has been neglected by palaeontologists. This leaves important questions unanswered:

  1. How has the deep biosphere changed over time? (Has it got bigger or smaller? Do different kinds of organisms dominate at different times in Earth history?)
  2. What controls the size (biomass) and productivity of the deep biosphere?
  3. How does the deep biosphere interact over time with groundwater, minerals, and the chemistry of the oceans and atmosphere?
  4. How can organisms become fossilized deep underground?
  5. How can we look for these fossils, and confirm that they are truly biological, genuinely indigenous to the subsurface, and ancient in origin?

What’s it got to do with Mars?

The world’s space agencies are currently preparing robotic missions to search for fossils on Mars. But for the last few billion years, the surface of Mars has been extremely cold, dry, caustic and irradiated. If there was life, it may have sheltered deep underground, where geothermal heat could keep water flowing. We can’t dig kilometres into Mars (it’s too expensive!) but we can look for fossils in minerals formed deep underground that later became exposed at the surface. My research asks:

  1. Can we find fossils of Mars-relevant organisms from Mars-like subsurface environments on Earth?
  2. What are the similarities and differences between Earth’s deep biosphere (and its fossil record) and any plausible deep biosphere on Mars (and its fossil record)?
  3. Can we pinpoint rock or mineral deposits on Mars that represent both (a) an ancient subsurface environment suitable for life, and (b) a good chance of fossilizing anything that lived there?
  4. Is it really worth targeting such fossils on Mars, or are we better off looking at rocks formed at the surface in the earliest history of Mars, when the surface was much warmer, wetter, and more hospitable than it became later?

How is my research conducted?

My research in Edinburgh involves: (1) the study of fossil material using microscopes and high-resolution analytical techniques; (2) experiments to understand how bacteria become fossilized; (3) computer modelling of the chemistry of subsurface environments; (4) synthesis of all of the above and relevant literature from many fields that contribute to my research questions.

This research began in October 2017. I will update this page with new developments as time goes by.