Department of Geosciences
                    State University of New York at Stony Brook

Planetary and Terrestrial Sedimentary Research
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    Nicholas Tosca                                     Department of Geosciences
   Graduate Student                                 SUNY Stony Brook
                                                                       Stony Brook, NY 11794-2100
                                                                       Ph: 631-632-1936
    Curriculum Vitae                                Fax: 631-632-8240

    B.S., Geology, State University of New York at Albany, 2001
    M.S., Geology, State University of New York at Stony Brook,     2003
    Ph.D., Geology, State University of New York at Stony Brook,     (in-progress)

My research interests are using experimental and theoretical geochemistry to better understand surface processes on Mars. Specifically, my focus is on understanding (1) the chemical weathering of basaltic materials on the Martian surface, and (2) evaporation processes on the Martian surface. This research is also applicable to several problems in environmental science.

(1) Chemical weathering of basaltic materials at the Martian surface:

Our focus is better understanding the chemical weathering process from two perspectives:

                   - Controls on fluid chemistry

                   - Controls on secondary mineralogy produced during chemical weathering

Generally, we take an experimental approach to investigating chemical weathering, by synthesizing our own “Martian” basalts of any desired composition, mineralogy or crystallinity. By using constraints on basalts analyzed at the Martian surface (e.g., from remotely sensed or in-situ data), we can synthesize basalts which are, in fact, quite uncommon on the Earth’s surface. Once the synthesis is completed and the basaltic materials are well-characterized, we conduct a variety of weathering experiments that can evaluate effects such as: open vs. closed hydrologic systems, temperature, atmospheric composition, and fluid composition. By taking a fundamental approach to understanding what controls solute acquisition and secondary mineral formation during chemical weathering, we can apply our results to those returned from various exploration missions to better interpret Martian surface mineralogy.

Selected Publications:
          Tosca, N.J., McLennan, S.M., Lindsley, D.H., Schoonen, M.A.A. (2004) Acid-sulfate weathering of           synthetic Martian basalt: The acid fog model
revisited, Journal of Geophysical Research, 109,           E05003, doi: 10.1029/2003JE002218.

          Tosca, N.J., Hurowitz, J.A., Melzer, L., McLennan, S.M., Schoonen, M.A.A. (2004) Olivine weathering           on Mars: Getting back to basics. In Lunar and Planetary Science XXXV, Abstract #1043, Lunar and           Planetary Institute, Houston (CD-ROM).

          Tosca, N.J.
, McLennan, S.M., Lindsley, D.H., Schoonen, M.A.A. (2003) Low-temperature aqueous           alteration on Mars: insights from the laboratory. In Sixth International Conference on Mars, Abstract           #3178, Lunar and Planetary Institute, Houston (CD-ROM).

(2) Evaporation processes at the Martian surface:

Saline mineral assemblages have been identified at the Martian surface in several locations, including Meridiani Planum, where evaporites have been subject to sedimentary processing. In addition, evidence for saline minerals also comes from SNC-type meteorite analyses which show that pre-terrestrial carbonate, sulfate and chloride minerals were indeed preserved.

By using data generated from our basaltic weathering investigations, we can evaluate controls on saline mineral formation during evaporative concentration, both theoretically and experimentally.

Our theoretical approach employs a geochemical modeling code investigating mineral equilibrium upon fluid evaporation. We employ the Pitzer ion interaction approach to calculating activity coefficients in these high-ionic strength, evaporating solutions. One complication, however, is that our results show chemically weathering Martian basalt typically results in high Fe concentrations, especially under acidic conditions. Therefore, we have constructed a Pitzer-based thermodynamic dataset which includes both Fe2+ and Fe3+ as additional components to allow the effects of redox disequilibrium to be considered in our calculations. The model has been tested to produce accurate results and provides much insight into fluid-mineral equilibrium in such unique geochemical systems.

Our experimental approach to evaporation processes at the Martian surface involves the full characterization of fluid chemistry and mineral precipitates during isothermal evaporation of basaltic-weathering derived fluids. We employ an apparatus which allows the effects such as temperature, atmospheric composition and redox disequilibrium to be evaluated during the evaporation experiments. In addition, the design of the apparatus allows more complicated processes typical of terrestrial evaporite sedimentation to be evaluated such as fractional crystallization and mineral recycling. Our unique equilibrium modeling code provides critical data on the departure from equilibrium with respect to precipitating mineral phases, allowing complicating kinetic effects to be identified.

Selected Publications:
          Tosca, N.J., McLennan, S.M., Clark, B.C., Grotzinger, J.P., Hurowitz, J.A., Knoll, A.H., Schröder, C.,           Squyres, S.W. (2005) Geochemical Modeling of Evaporation Processes on Mars: Insight from the           Sedimentary Record at Meridiani Planum. Earth and Planetary Science Letters, 240, 1, 125-151, doi:           10.1016/j.epsl.2005.09.042.

          Tosca, N.J. and McLennan, S.M. (2006) Chemical divides and evaporite mineral assemblages on           Mars. Earth and Planetary Science Letters, 241, 1-2, 21-31, doi: 10.1016/j.epsl.2005.10.021.

          Tosca, N.J. and McLennan, S.M. (2006) Experimental constraints on evaporation processes at           Meridiani Planum. In Lunar and Planetary Science XXXVII, Abstract #2260, Lunar and Planetary           Institute, Houston (CD-ROM).

          Tosca, N.J. and McLennan, S.M. (2006) Constraints on evaporation processes at Meridiani Planum:           Combining theoretical and experimental data. In Lunar and Planetary Science XXXVII, Abstract           #2278, Lunar and Planetary Institute, Houston (CD-ROM).

Mars Exploration Rover (MER) Mission:

In April 2004, I was named a student collaborator for the Mars Exploration Rover (MER) mission, which was launched in the summer of 2003 and began surface operations in January of 2004. From April to August of 2004, I worked at the Jet Propulsion Laboratory in Pasadena, California with the Athena Science team building science plans and planning various experiments with the rovers. I worked with both the Opportunity and Spirit rovers and among the science plans I had helped build that were implemented were plans for digging the third trench in Gusev Crater, which Joel Hurowitz and myself named “The Boroughs”, in honor of New York City. We also planned the science observations in the newly dug trench, using the APXS and Mössbauer spectrometers and microscopic imager. Interestingly enough, the trench revealed some of the highest SO3 abundances measured at Gusev Crater. I am still a student collaborator and am still involved in planning science activities for the two rovers here at Stony Brook.

I was also involved in assessing the limits of mobility of the rovers which was necessary prior to Opportunity’s entry into Endurance crater. This involved re-constructing a portion of the exposed outcrop on the crater wall which the rover would have to drive over at various slopes (tested up to 50 degrees). Here is a video which was made at JPL showing how the mobility testing was done:

“Entering Endurance Crater” video – June 21, 2004

I was lucky enough to participate in a Mars Exploration Rover mission press briefing on June 25, 2004. Here is the link to the video and some links to the press release:

Mars Rover Surprises Continue; Spirit, Too, Finds Hematite (NASA Press Release)

Spirit Finds Hematite, Opportunity Discovers Signs of More Water (The Planetary Society)

“Mars Rovers: Energizer Bunnies of Planetary Exploration” (Stony Brook University – Office of the Vice President for Research)