Dan Johnson, PhD

About Me

I am a geochemist by training and am currently supporting the Defense POW/MIA Accounting Agency as an Isotope Mass Spectrometrist with SNA International. I am using my expertise to support the DPAA's mission of providing the fullest possible accounting for missing U.S. personnel to their families and the nation. In practice, I prepare and isotopically analysis samples from recovered individual remains to assist with their identification and repatriation to families. I previously worked as a Postdoctoral Research Associate in the lab of Mark Torres at Rice University and completed my PhD thesis at Caltech in October 2020 under the mentorship of Jess Adkins. My thesis research focused on the using sulfur isotopes to understand processes in the modern and ancient marine sulfur cycle. More broadly, I am interested in reconstructing past Earth surface processes and chemical fluxes using the geochemical study of sedimentary materials. Our understanding of how these processes have operated in the past informs our predictions of how the processes may respond to future changes to the Earth system (especially anthropogenic global warming).


In my new role with the DPAA, I have become interested in developing novel isotopic approaches for application within the forensic sciences. Although the light stable isotopes (hydrogen, carbon, nitrogen, oxygen, and sulfur) have been used in forensic studies for decades, other isotopic systems remain largely unexplored (with the notably exception of strontium). Please feel free to contact me with ideas for potential applications and opportunities for collaboration.

Within the geosciences, I am driven by a desire to understand how Earth's surface processes have varied through time and, in turn, how variations in these processes have affected life and climate. To do this, I have used the geochemical analysis of sedimentary materials combined with mathematical modeling. This combination of measurements and modeling  has helped me answer two basic questions about any period in Earth's past: "What happened?" and "How did it happen?". My PhD thesis focused on these questions in the context of sulfur isotopes in sedimentary materials. My postdoctoral research switched gears to study the controls on nutrient input and organic matter preservation in natural sediments.

Read more about my past and present research here.


My first two journal articles were published in the journal Earth & Planetary Science Letters and can be found here. Further articles are in developed and will be added to this list as they are published.

Curriculum Vitae

You can learn more about my professional background by downloading my Curriculum Vitae (last updated July 24th, 2022).


I am passionate about increasing diversity and inclusion, mental health awareness, and public outreach within the geosciences. I also enjoy learning about and implementing new pedagogical strategies shown to increase educational equity and effectively engage students in the classroom. You can learn more about some of the work I've done and cool resources I've come across here.

Fun Stuff

I have many hobbies outside of my research work. I enjoy playing music, long distance running, camping, hiking, and reading literature. See this page for some fun photos and more.

Contact Me

Due to the ongoing COVID-19 pandemic, I am most accessible by email and social media. Please see the footer banner for links to my email, my LinkedIn page, and my Mastodon page. Looking forward to hearing from you!