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SUMMARY:Evolving Concepts of Planetary Habitability from Earth Analogue En
 vironments    - Barbara Sherwood Lollar\, University of Toronto
DTSTART:20240124T160000Z
DTEND:20240124T170000Z
UID:TALK205582@talks.cam.ac.uk
CONTACT:Dr Emily Mitchell
DESCRIPTION:The challenges of the green energy transition to address the e
 ver-increasing effects of climate change has raised the profile of natural
 ly-occurring geologic hydrogen accumulations in the crust – but the foun
 dational research on this phenomenon arose from investigations focused on 
 life forms other than humans. Only recently have human populations begun t
 o consider competing with their microbial cousins for this subsurface hydr
 ogen resource on a global scale. Over the past few decades\, Earth analogu
 e studies has revealed previously unexplored localities and unexpected pro
 cesses that have challenged us to think more broadly and universally about
  the fundamentals of habitability. Scientists investigating microbial comm
 unities identified water-rock chemical reactions such as serpentinization 
 and radiolysis that produce critical electron donors (e.g. hydrogen) and e
 lectron acceptors (e.g. sulfate) capable of sustaining chemolithotrophic m
 icrobial communities in the oceanic and terrestrial crust. Such processes 
 of water-rock reaction have now been shown to be a major driver H and S cy
 cles in the subsurface of the planet\, and increasingly their role in the 
 deep C cycle is being investigated.  \n\nSubsurface “rock-eating” micr
 obial communities have been shown to be sustained on long time scales\, is
 olated from the surface hydrologic cycle. Both field and laboratory discov
 eries are expanding the spectrum of water-rock reactions that drive the H\
 , S and C deep cycle and provide mechanisms for sustaining deep subsurface
  life in the absence of interaction with a surface photosphere. Discussion
 s of habitability typically focus on the necessity for fluid mixing and/or
  spatial geochemical gradients\, but recent discoveries suggests apparentl
 y thermally and spatially “stagnant” systems may still be habitable th
 rough radiolysis. Taken together\, insights from terrestrial analogue site
 s suggest new potential models for planetary habitability capable of susta
 ining chemolithotrophic life on planets where photosynthesis may never hav
 e arisen. These terrestrial discoveries have catalysed an expanded search 
 for habitable environments on planets\, exoplanets and moons to include no
 t only surface based life but potentially vast subsurface biospheres.  
LOCATION:Martin Ryle Seminar Room\, Kavli Institute
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