Humble beginnings in a one-room grade school in rural Montana led Trinity Hamilton to look to the stars. Now, as a NASA Postdoctoral Program Fellow with the NASA Astrobiology Institute, she brings her focus back to the ground to help expand our knowledge of the emergence of life on Earth.

"Understanding the role of biology in planetary evolution remains a daunting challenge to astrobiologists," she said. "We aim to better understand the co- occurrence of physiological strategies employed by microorganisms in early Earth analogs, and how and why signatures from these populations end up in the rock record."

Hamilton joined her mentor, Jenn Macalady, with the NAI team at Pennsylvania State University, though she spends much of her time at Little Salt Spring, her main field site in North Port, Fla. Formed thousands of years ago after the last ice age, Little Salt Spring is a karst sinkhole - formed from the dissolution of limestone - that is rich in artifacts that help researchers date human occupation in Florida.

By collecting samples from this field site, Hamilton hopes to learn about and increase our understanding of ancient life on Earth. Microorganisms leave very poor fossil records, so understanding the deposition of biosignatures is important. Ultimately, she aims at determining the role of photosynthesis in the rise of oxygen on early Earth before, during and after the Great Oxidation Event, or when free oxygen (O2) first appeared in Earth's atmosphere.

"An intricate balance between oxygenic and anoxygenic photosynthesis may have played an important role in oxygenation of the atmosphere on early Earth," she explained. "Examining this relationship in environments with conditions that are similar to those thought to have been present on early Earth is greatly enhancing our understanding of the role of prokaryotic photosynthesis in maintaining low levels of oxygen through the Proterozoic eon."

This research, Hamilton pointed out, will also greatly enhance the interpretation of biological markers in ancient rocks, revealing clues about both the metabolic capabilities of the organisms and the overlying geochemical conditions present at the time of deposition.

In addition to frequenting Little Salt Spring, Hamilton had the opportunity to travel to the Max Planck Institute for Marine Microbiology in Germany where she was trained in Dr. Dirk de Beers group to use microsensors that are necessary for measuring geochemical parameters on a very fine scale. These tools allow her to examine microbial physiology and better interpret how microbial activities may result in global consequences.

"Using microsensors to measure oxygen and sulfide concentrations in real-time allows me to test whether the cyanobacterium that I have isolated from Little Salt Spring is able to switch between oxygenic and anoxygenic photosynthesis," she said.

"By processing and understanding large and complex molecular datasets, I have gained valuable insights into the interplay between microorganisms and their environment and developing better tools to examine these interactions, both in situ and in laboratory experiments."

Hamilton eventually broke away from rural Montana when she was accepted to Montana State University in Bozeman, Mon. During her graduate studies, she had the opportunity to collaborate with Eric Boyd, a former NAI Fellow, and learn about NPP directly from a Fellow. The team examined carbon and nitrogen cycling in extreme environments, including thermal features in Yellowstone National Park and an alpine glacier in Canada.

"I wanted to have an opportunity to continue research in the field of astrobiology and develop as a geobiologist," she said. "Being exposed to research and problems on the fringe of my expertise is both exciting and motivating, especially as an early-career scientist. Being an NPP Fellow has given me the freedom to do research that I am very excited about."

Once she completes her fellowship, Hamilton plans to use the experiences and knowledge she gained to propel her into a professorship at a leading university, building and leading a research group of her own.