I am currently working on three projects that will eventually make up the three chapters of my PhD. All of my projects focus on how organic matter is altered when it interacts with its environment.
Previous work has shown that weak sorption interactions between organic molecules and solid filter phases can impart a small C isotope effect. Additionally, modeling work suggests that H isotopes are sensitive to local electron distributions that are affected by sorption interactions. As a result, it is possible that the preservation of organic molecules by sorption to mineral surfaces alters their isotopic composition. To test this I am sorbing organic molecules to mineral surfaces and measuring isotope fractionation. This work has implications for studies that rely on isotope composition such as paleo-temperature reconstructions or source identification.
Isotopes are atoms that have the same number of protons but a different number of neutrons. The amount of rare isotopes in an organic molecule can tell scientists a lot of things, such as where the molecule came from or how cold it was when the molecule formed. However, to use isotopes as a tool scientists need to understand the processes that affect a molecule's isotope distribution. Organic molecules often stick to mineral surfaces and it's possible this process affects their isotope distribution. I am testing this theory sticking organic molecules to minerals and seeing if their isotope distribution changes.
Despite predictions of higher organic matter content due to meteoric delivery, only low concentrations of chlorinated hydrocarbons have been detected in Martian soils. The lack of organics is partially due to exposure to radiation or oxidants present in the soil breaking down organic material. However, its is possible that radiation exposure also produced metastable organic molecules that are not amenable to pyrolysis gas chromatography mass spectrometry techniques, such as organic acids. To test this theory, I am exposing characteristic meteoric organic matter to 200 MeV protons and identifying metastable products. This work has implications for future Mars missions that are focused on detecting organic material.
We have sent several rovers to Mars to look for evidence of past life in the form of organic molecules. However, the rovers have only found small amounts of organic molecules, much less than what scientists were expecting. Even if life never existed on Mars, we still expect organic molecules to be there from meteorite impacts. One possible explanation as to why we haven't found organic molecules on Mars is we are sending the wrong type of instrument. Radiation on Mars could be changing the organic matter into organic acids, which require a different type of instrument to measure. I am going to expose organic matter, similar to what we see in meteorites, to radiation and see what types of organics are produced.
Position specific isotope analysis is already widely used in the food and drugs sciences and is becoming mainstream in geochemistry applications. Its use in geochemistry requires that we understand processes that could affect these intramolecular isotope pattern. I am currently developing a molecular model to predict intramolecular isotope patterns organic molecules sorbed to mineral surfaces.
Scientists are now using the position of a rare isotope within a molecule to infer information about how a molecule formed. To do this, we have to understand how different processes could change where a rare isotope ends up. I am making a computer model that will help us predict how the position of rare isotopes change when the molecule sticks to another surface.
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