Each year, graduating seniors majoring in EAPS present a thesis in completion of their Bachelor of Science Degree. This year we had a class of seven students specializing in areas across the earth, atmospheric and planetary sciences.
Natural Variability in Eastern Tropical Pacific Nitrous Oxide Emissions Elisabeth Boles (advisor Prof. Andrew Babbin)
Research: I examine the temporal and spatial patterns in atmospheric concentrations of nitrous oxide over the Pacific Ocean, in order to understand the importance of oxygen minimum zones in the eastern tropical Pacific on marine N2O emissions, as well as how natural emissions vary between El Nino and La Nina periods.
What's Next: "I'll be working in an oceanography lab (Austral Boreal Carbon at LOCEAN) in Paris!"
Investigation of the Heterogeneous Ice Nucleation Potential of Sea Spray Aerosols Lily Dove (advisor Prof. Dan Cziczo)
Research: Sea spray is the largest aerosol source on Earth. Bubble bursting mechanisms at the ocean surface create smaller film burst and larger jet drop particles. These two assemblages of particles have different chemical properties which impact how effectively they activate as ice nucleating particles. Ice nucleating particles go on to form high-altitude tropospheric ice clouds and additionally contribute to mixed-phase cloud glaciation, which are important factors in global climate. In this study, we used cultures of Prochlorococcus, one of the most abundant phytoplankton species in the global ocean, to act as model source of organic sea spray aerosols. We quantified the ice nucleation potential of single component organic molecules that mimic Prochlorococcus proteins, lipids, and saccharides to explore the role of chemistry in the successful activation of Prochlorococcus culture particles. Ultimately, the findings can be used to help develop an understanding of how changes in the marine system, such as ocean acidification, may impact the global climate system.
What's Next: "I will be pursuing a Ph.D. in Environmental Science and Engineering at Caltech"
Modeling Methylmercury in Maine‚ Äôs Tribal Meres Nick Hoffman (advisor Prof. Noelle Selin)
Research: The Wabanaki traditional-subsistence diet, marked by extensive consumption of fish, is rendered potentially dangerous by the bioaccumulation of the globally distributed toxicant methylmercury (MeHg) in fish from tribal lakes. To investigate the potential health impact of MeHg on the Wabanaki subsistence diet, MeHg concentrations in twenty Maine tribal lakes were modeled for the year 2035 under three different policy scenarios. The model was calibrated for parameters specific to the Maine environment - e.g. the methylation rate constant - using a factorial analysis. A least squares regression performed on the modeled results before and after calibration demonstrated a slight improvement in model accuracy following calibration. (The modesty of this improvement suggests that some of the model parameters may require calibration specific to the particular lake, rather than the general region.) The model predicts that the strictest global Hg regulations will reduce the concentration of MeHg in these twenty Wabanaki lakes most dramatically - on average, by 22.10% for the year 2035, as compared to 14.51% and 4.69% projected for the other two scenarios modeled. The more that MeHg is reduced, the healthier it becomes for the Wabanaki to pursue a traditional-subsistence diet.
What's Next: "Still working on my research!!"
Identifying Binary Central Stars of Planetary Nebulae with Kepler K2 Campaign 11 Photometric Data Jonathan Hurowitz (advisor Dr. Amanda S. Bosh and Dr. George H. Jacoby [Lowell Observatory])
Research: Planetary nebulae are large clouds of ionized gas ejected from certain stars at the end of their stellar evolution cycle, and most planetary nebulae have unusual, and often asymmetric, shapes. There are two main theories for the development of these unusual morphologies, one of which is gravitational shaping from binary interactions with another star or planet. Hurowitz programmed a software pipeline to search for periodicity in the photometric data of 140 planetary nebulae, a larger sample than ever before analyzed, in the highly-accurate Kepler K2 campaign 11 data to confirm this theory. Since our sun will probably create a planetary nebula when it begins to run out of fuel in about 5 billion years, this research can shed light on the shape of the planetary nebula that will one day replace the Earth!
What's Next:"I will be attending Stanford Law School."
Methane and Carbon Cycling in Soils of the Harvard Forest Alexa Jaeger (advisor Prof. Colette Heald)
What's Next:"Strategy Analyst at Accenture Strategy in Chicago."
Sublimative Torques as the Origin of Bilobate Comets Taylor Safrit (advisor Dr. Amanda S. Bosh)
Research: Modeled sublimative torqueing on Centaurs through their dynamic evolution to determine whether magnitude of angular acceleration large enough to spin Centaurs past critical point, causing potential breakup and reformation in bilobate structure.
Development of a Leaching Procedure for Isotopic Study of Metal/Silicate Partitioning Experiments Mary Spanjers (advisor François Tissot)
Research: One major step in the formation of rocky planets is differentiation: i.e., the separation of metal and silicate melts resulting in the segregation of a large metallic core. During the differentiation process, some elements will preferentially be incorporated into the metal or silicate phase, depending on their geochemical characteristics. This elemental fractionation might be accompanied by an isotope fractionation, which would lead to different isotopic composition in the final metal and silicate reservoirs. Recently, the existence of isotope fractionation has been invoked for uranium to explain results obtained on some iron meteorites. If true, isotope fractionation during metal/silicate partitioning would affect both the dating of iron meteorites (which uses uranium isotope ratios) and provide us with a means to constrain the budget of heat-producing elements in the inner core (radioactive uranium isotopes produce heat). To confirm the claim that differentiation can fractionate uranium isotopes we selected 16 well-characterized metal/silicate experimental charges. We used these samples to test a step-leaching protocol (from 2.5M HCl to concentrated HF) that were designed to selectively digest metal or silicate fractions, and present the resulting U release pattern. The depleted nature of the U used in these experiment precludes any possibility to obtain sufficiently high precision isotopic data. Nevertheless, the release patterns of U obtained suggest that the leaching protocol developed here could be used on samples with natural U isotopic composition to quantify the extent of isotope fractionation of uranium, and possibly other elements, between the metal and silicate fraction.
What's Next:"Field Engineer at Schlumberger"
Photo credit: V. Mckenna
Special thanks, as always, to Jane Connor, EAPS' Lecturer from Writing Across the Curriculum, for her work supporting and coaching this year's graduating class. Connor, who provides one-on-one writing and effective presentation support to EAPS undergraduates as well as undergraduates in other courses, holds a BA in English from Swarthmore College, and an MA in Languages, Literature and Communication, with an emphasis on Communication Theory, from Columbia University.