Joshua Sebree

Associate Professor - Astrochemistry, Astrobiology

Joshua Sebree

213 McCollum Science Hall

(319) 273-2617

Joshua Sebree

Associate Professor - Astrochemistry, Astrobiology

2011-2013 Postdoc, Goddard Space Flight Center, NASA (with Melissa Trainer)

2011 Ph.D. Physical Chemistry, Purdue Univeristy (with Timothy Zwier)

2006 B.S. Chemistry, The University of Kansas

Research Interests

My research program falls into two categories.  Part of my work aims to explore the new aspects of prebiotic and Titan-like aerosols and their importance both in interpreting data from NASA missions and in understanding how biological molecules may form in abiotic environments.  The other part is exploring the chemistry that gives rise to and sustains life in astrobiological field environments, such as caves.

1. The effect of trace species on bulk aerosols
The majority of Titan aerosol studies start with a premix of several percent methane in nitrogen. This premix is then exposed to an energy source to initialize reactions. The resulting aerosols are then characterized using a variety of methods including infrared (IR) spectroscopy and mass spectrometry (MS). While this “Titan Standard” mixture is a good starting point, from the Cassini mission, it is becoming evident that other atmospheric constituents should be taken into account. Data from the Cassini spacecraft has allowed for the identification of numerous trace (>1%) species in Titan’s atmosphere including acetylene (C2H2), carbon monoxide (CO), hydrogen cyanide (HCN), cyanoacetylene (HC3N) and benzene (C6H6), to name a few. Preliminary results from my current study demonstrates that the photolysis of larger aromatics (naphthalene and quinoline) at ppm levels leads to the formation of large poly-aromatic systems containing eight or more aromatic rings. We have also demonstrated that far-IR (50-600 cm-1) spectra of these new aerosols have features similar to those observed by Cassini that have not been match previously by laboratory-created aerosols. Building upon this work, my research group is focusing on how trace compounds, such as cyanoacetylene and HCN interact with these aromatic seeded aerosols and how they may lead to the incorporation of nitrogen and possible formation of PANHs within the aerosols.

2. Cave Research
Wind Cave national Park represents a unique opportunity to study an accessible, yet isolated, extremophile ecosystem.  The cave is one of the oldest (>300 Myr), longest, and most complex cave systems in the world.  With over 150 miles of mapped passageways, Wind Cave serves as the only natural access to the Madison formation aquifer via a series of lakes in the deepest section of the cave.  These lakes contain an isolated, nutrient-limited biome that may serve as the most accessible natural analog for low-biomass aqueous environments such as the oceans of Enceladus and Europa.  Access to these lakes requires climbing and crawling ~3 km underground through passageways as small as 20 cm, limiting the amount of anthropomorphic contamination from human visitors.  All living organisms require three things to survive: sources of energy, water, and nutrients.  Extremophiles are organisms that have evolved to live in environments that severely lack one or more of these.  Given the limited nutrients available in Wind Cave, microbial life found deep i the cave is expected to make extreme adaptations to survive.  Samples from water in the cave are being tested and cultured.  This will tell us about what life can thrive in the extreme environment of the cave, and is critical in determining what types of organisms can be found in other extreme environments.

Professional Accomplishments


Sebree JA, Stern JC, Mandt KE, Domagal-Goldman S, Trainer MG. "13C and 15N Fractionation of CH4/N2 Mixtures during Photochemical Aerosol Formation: Relevance to Titan” Icarus, 2015, DOI:10.1016/J/Icarus.2015.04.016.
Sebree JA, Trainer, MG, Loeffler MJ, Anderson CM. "Titan Aerosol Analog Absorption Features Produced from Aromatics in the Far Infrared" Icarus, 236: 146-152, 2014.
Trainer MG, Sebree JA, Yoon YH, Tolbert MA. “The influence of benzene as a trace reactant in Titan aerosol analogs”. The Astrophysical Journal Letters, 766:L4, 2013
Sebree JA, Kidwell NM, Amberger BK, Selby TM, McMahon RJ, Zwier TS. “Photochemistry of Benzylallene: Ring-closing Reactions to form Naphthalene”. Journal of the American Chemical Society, 134 (2): 1153-1163, 2011.
Sebree JA, Zwier TS. “The Excited States and Vibronic Spectroscopy of Diphenyldiacetylene and Diphenylvinylacetylene”. Physical Chemistry Chemical Physics, 14 (1): 173-183, 2011.
Sebree JA, Plusquellic DF, Zwier TS. “Spectroscopic Characterization of Structural Isomers of Naphthalene: 1-Phenyl-1-butyn-3-ene”. Journal of Molecular Spectroscopy, 270 (2): 98-107, 2011.
Sebree JA, Kidwell NM, Buchanan EG, Zgierski MZ, Zwier TS. “Spectroscopy and ionization thresholds of -isoelectronic 1-phenylallyl and benzylallenyl resonance stabilized radicals”.Chemical Science, 2 (9): 1746-1754, 2011.
Sebree JA, Kislov VV, Mebel AM, Zwier TS. “Isomer specific spectroscopy of C10Hn, n=8-12: Exploring pathways to naphthalene in Titan's atmosphere”. Faraday Discussion, 147: 231-249, 2010.
Sebree JA, Kislov VV, Mebel AM, Zwier TS. “Spectroscopic and Thermochemical Consequences of Site-Specific H-Atom Addition to Naphthalene”. The Journal of Physical Chemistry A, 114 (21): 6255-6262, 2010
Lehnig R, Sebree JA, Slenczka A. “Structure and Dynamics of Phthalocyanine‚Argonn (n = 1-4) Complexes Studied in Helium Nanodroplets”. The Journal of Physical Chemistry A, 111 (31): 7576-7584, 2007