Energy Flow and Life: A Thermodynamic-Kinetic View of Biology in Its Relationship With the Environment
When: March 1, 2010 11AM PST
Life’s unique and universal relationship with energy flow offers an added constraint in conceptualizing and quantifying habitability and biosignatures, the central concepts in the search for life beyond Earth. The statement, “life requires energy”, is widely accepted and often invoked in astrobiology, but is of little practical use given that energy – in one form or another, and at one level or another – is present everywhere in the universe. However, qualification and constraint are introduced by considering the unique attributes of life’s dependence and effect on energy flow, at physical, chemical, and biological levels of specificity. Life’s relationship with energy has both thermodynamic and kinetic dimensions: how much and how fast are both important, where energy demand, availability, and transduction are concerned. When considered in concert, these two dimensions yield significant resolving power in quantifying life’s need for energy (a constraint on habitability) and life’s imprint on energy flow (a form of biosignature). They do so at a fundamental point of interface between life and its host environment, and in a fashion that need not be specific to Earth-type life. This approach will be described at a conceptual level, and then applied to the specific example of habitability of serpentinizing systems for methanogenic organisms.