John R. Haas

Johnson R. Haas

Associate Professor
Aqueous Geochemistry, Geomicrobiology

1129 Rood Hall
(269) 387-2878
FAX (269) 387-5513

Education

Ph.D. 1993, Washington University in St. Louis
B.Sc. 1988, Auburn University
Associate Professor in the WMU Environmental Studies Program

Courses Taught

ENVS 2150 - Environmental Systems and Cycles
GEOS 2000 - Evolution of Life, A Geologic Perspective
GEOS 5550 - Introduction to Geochemistry

Research

Aqueous Geochemistry, Astrobiology
My research focuses on the geochemistry of microbial-mineral interactions, the effects of microbial processes on planetary geochemistry, and the likely attributes of biogeochemical processes on exoplanets where life occurs. Microbes on Earth display a remarkable diversity of metabolic processes that sustain growth and replication, including heterotrophic metabolisms capable of respiring with a wide range of metals, metalloids and non-metals, and autotrophic metabolisms that sustain primary production through photosynthetic and chemosynthetic pathways. This observed metabolic diversity among biota on just one planet (Earth) suggests that geochemically-emergent replicators (life) may potentially obtain electrochemical energy for growth using any chemical reaction pathway that is thermodynamically favored but kinetically inhibited under local conditions. It is very likely that the spectrum of microbial metabolic pathways observed on Earth represents only a subsample of all possible and feasible metabolisms that occur within the population of exoplanet biospheres. My research examines the potential feasibility of alternative biochemistries and metabolic pathways that may occur on exoplanets and which may engender planetary geochemical conditions that depart radically from those found on Earth. Hundreds of exoplanets are known to exist, and many of them occur in the habitable zone of their star, where liquid water may be stable at or near the surface. By examining potential alternative biochemistries and assessing their thermodynamic plausibility and geochemical feasibility, we can develop better-informed expectations of how biota may influence host planets in ways that are detectable by remote observation, greatly facilitating our search for life elsewhere in the universe.

Ongoing Projects
• Theoretical studies of the thermodynamic properties of potential autotrophic metabolic processes that could feasibly sustain primary productivity within exoplanet biospheres.
• Examination of alternative biochemistries and formats for genetic replication involving non-aqueous solvents under exotic geochemical conditions.
• Assessment of the likely geochemical consequences of biospheres dominated by alternative metabolic processes on exoplanet atmosphere/hydrosphere/surface chemical compositions.

Recent Publications

Haas (2010) The potential feasibility of chlorinic photosynthesis on exoplanets. Astrobiology 10(9), 953-963.

Haas J. R. and Purvis O. W. (2006) Lichen biogeochemistry, in Fungi in Biogeochemical Cycles, G. M. Gadd, ed. Cambridge University Press, 490 p.

Haas J. R. and Northup A. (2004) Effects of aqueous complexation on reductive precipitation of uranium by Shewanella putrefaciens. Geochemical Transactions 5(3), 41-48.

Haas J. R. (2004) Effects of cultivation conditions on acid-base titration properties of Shewanella putrefaciens. Chemical Geology 209, 67-81.

Haas J. R. and DiChristina T. J. (2002) Effects of Fe(III) chemical speciation on dissimilatory Fe(III) reduction by Shewanella putrefaciens. Environmental Science and Technology 36, 373-380.

Haas J. R., DiChristina T. J., and R. Wade J. (2001) Thermodynamics of U(VI) sorption onto Shewanella putrefaciens. Chemical Geology 180, 33-54.

Haas J. R. and Shock E. L. (1999) Halocarbons in the environment: Estimates of thermodynamic properties for aqueous chloroethylene species and their stabilities in natural settings. Geochimica et Cosmochimica Acta 63(19/20), 3429-3441.

Haas J. R., Bailey E. H., and Purvis O. W. (1998) Bioaccumulation of metals by lichens: Uptake of aqueous uranium by Peltigera membranacea as a function of time and pH. American Mineralogist 83(11-12, Part 2), 1494-1502.

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