Föreläsning med Sean McMahon
- Datum: –17.00
- Plats: Geocentrum
- Föreläsare: Sean McMahon
- Arrangör: Institutionen för geovetenskaper, Uppsala universitet
- Kontaktperson: Anna Neubeck
The Search for a Fossil Deep Biosphere on Mars: Three Challenges
The Martian surface has been cold and predominantly dry for at least the last three billion years and is an extremely challenging environment for life. However, the subsurface could have sustained stable reservoirs of geothermally heated liquid water for much of this time, providing a protected habitat with its own sources of energy and nutrients, analogous to autotrophic ecosystems in the “deep biosphere” on Earth. Since Earth’s deep biosphere appears to have a fossil record, it has been suggested that our best chance for finding life on Mars is to send rovers to look for similar fossils in martian rocks exposed from great depths. Here, I will present three objections to this proposal. First, it is unclear whether known fossils from Earth’s deep biosphere are good analogues for any deep biosphere on Mars. Second, it is unclear how to optimise the search for an ancient martian deep biosphere, which is unlikely ever to have been global in extent; mineralized fractures and pores are mostly too small to resolve from orbit, and most are unlikely to be fossiliferous. Third, lacustrine mudstones on Mars — already shown to represent palaeohabitats capable of preserving organic matter — seem to offer a much more compelling target in the near term. Despite these objections, I will conclude that more work on the fossil record of Earth’s deep biosphere, especially as an analogue for Mars, is urgently needed.