Graduate Students

Val Aguilar

Val Aguilar

1st Year Ph.D Student
She/Her/Hers

Val received her BS in Earth Sciences (paleobiology & geology) from UC Santa Barbara in 2021. As an RA at Johns Hopkins University, she became interested in using lab and field techniques to answer questions related to perturbations in Precambrian biogeochemical cycles. At Harvard, Val works in the Drabon & Johnston lab groups, where she hopes to use isotope geochemistry and sedimentology as tools to characterize disturbances on early Earth. Her research currently involves unravelling how the Archean biosphere and surface environment changed as a result of large extraterrestrial impacts.

Ana Gonzalez Valdes

Ana Gonzalez Valdes

5th Year Ph.D Student

Ana Gonzalez Valdes received her B.A. in Earth Sciences from Columbia University in 2016. At Columbia and Caltech she worked to understand how microbes in unique environments cycle nutrients like phosphorus and sulfur. At Harvard Ana will be spanning the Johnston and Pearson labs and hopes to dig deeper into microbial nutrient cycling and how it can be measured isotopically.

Daianne

Daianne Höfig

1st Year Ph.D Student
She/Her/Hers
My name is Daianne, and I am originally from Brazil, where I obtained a BSc in Geology and an MSc in Geochemistry. During my studies at Texas A&M University, I transitioned from U-Pb zircon geochronology to organic geochemistry. Isotopes are my favorite tools to (1) research how biogeochemical cycles operated in past climate systems and (2) anchor these key climate events to precise timeframes. As a member of the Johnston lab, I aim to become proficient in using stable isotope geochemistry to address geobiological questions across different time scales and numerical modeling.

Ella

Ella Hughes

3rd Year Ph.D. Student
Ella is coming to Harvard from the UK, where she completed a BA degree in Natural Sciences and MSc degree in Earth Science at the University of Cambridge. Her Master’s research at Cambridge and Caltech focussed on the sulfur isotope composition of organic matter, and as part of the Johnston lab she is hoping to expand her knowledge of stable isotope geochemistry as a tool to approach biogeochemical questions.
K Keller

Katherine Keller

4th Year Ph.D Student
She/Her/Hers
Katherine received her BA in Environmental Chemistry from Columbia University in 2014. Since then, she has worked at the US Geological Survey on Quaternary paleoceanogprahic and hydroclimate reconstruction in the Arctic. At Harvard, she will be working in the Johnston and Schrag labs.
Haley

Haley Olson

3rd Year Ph.D. Student
She/Her/Hers
Haley received a BA in Geology from Carleton College in 2017. Haley's research uses stable isotope geochemistry to constrain marine geochemical conditions throughout geologic time (thus far from the Archean to the Neogene). She is currently focused on the Paleozoic and understanding how the sulfur cycle responded to the proliferation of land plants and how sediments record large volcanic events.