People: Astrobiology Graduate Students

Eva Stueeken
Earth & Space Sciences

Dass ich erkenne, was die Welt im Innersten zusammenhält (J.W. v. Goethe, Faust I, 1808, v. 382) – "So that I may perceive whatever holds the world together in its inmost folds."

This admittedly ambitious statement by one of my German forefathers describes very well my desire to understand the complexity of the world around us, the processes that have led to its formation and the laws of nature that will determine whether or not we are alone in the Universe.

As a foreign student in the UW Astrobiology program, I enjoy working in an international and interdisciplinary environment where these fundamental questions are addressed from all angles and where collaborations across departmental boundaries are highly encouraged.

My personal expertise lies in inorganic geochemistry, and I'm particularly interested in stable isotope fractionation. Isotopes of the same element generally show the same chemical behavior, but tiny differences in bond energies can accelerate or stabilize the heavier or lighter isotopes in certain reactions. For example, bacteria reducing sulfate to sulfide or selenate to selenide during respiration preferentially use the lighter isotopes.

Together with Roger Buick and Bruce Nelson, I am trying to measure microbially induced isotopic fractionation of sulfur and selenium recorded in ancient sediments and to use it as a proxy for the level of sulate and selenate throughout Earth's history. Both species would not be present in significant amounts without an oxic atmosphere, which in turn has probably been an essential condition for the rise of animals and intelligent life. The sulfur and selenium cycle together will help us unravel the timing of atmospheric oxygenation and thus shed light on biological and planetary evolution on Earth, which we hope to be an average chunk of rock in space.