DSC_1838 Dr. Sarah Stewart Johnson (PI)

I’m an associate professor at Georgetown University and a visiting scientist at NASA’s Goddard Space Flight Center.  I’m fortunate to get to work with some amazing people!  At present, my lab includes:

unnamed Dr. Maëva Millan
I am a postdoctoral fellow working on the chemical and mineralogical composition of the Martian surface using the Sample Analysis at Mars (SAM) experiment
onboard the Curiosity rover of the MSL mission. In particular, I am searching for organic molecules and biomarkers on Mars and investigating methods of their preservation in various kind of Martian minerals. In addition to data collected from SAM, I work with Martian analog samples from terrestrial environments. I recently received my Ph.D in specialty Astronomy and Astrophysics in France on a similar project. My daily laboratory experiments are physio-chemical analysis using
pyrolysis and wet chemistry coupled to gas-chromatography mass-spectrometry. I try to replicate SAM conditions as closely as possible to help data interpretation and the search of organic matter. Besides work, I love hiking and taking pictures of the beautiful places, landscapes and people I meet during my trips.
IMG_5836 Dr. Lu Chou
I am a NASA Postdoctoral Program (NPP) Fellow primarily based at NASA
Goddard Space Flight Center and the Johnson Biosignatures Laboratory. It was my endless fixation on the search for life in the universe that serendipitously (or
perhaps inevitably) led me to work on the Laboratory of Agnostic Biosignatures project. Though formally trained in organic geochemistry and microbiology, my current research is focused on understanding the relationship between chemical complexity and mass spectrometry data obtained from flight-capable instruments. I use both computational and experimental tools to look for potential biosignatures without assuming the presence of a specific biochemistry on other planetary bodies like Mars or Titan. Outside of my academic life, I enjoy the outdoors, hiking,
camping, biking, sewing, and traveling. I am also an astronomy enthusiast.
unnamed Nicole Wagner
I am a Ph.D student in the Johnson Biosignatures Lab. After receiving a B.S. from Stanford in physics with a focus on astronomy and a B.S. from Portland State
University in biology, I decided to merge my interests in the study of life in extreme environments used as Mars analogs here at Georgetown. My foray into the world of extremophiles began in Anna-Louise Reysenbach’s lab at Portland State University where I spent my days sifting through the genome of hyperthermophilic archaea. In my free time, I re-watch episodes of Star Trek, obsess over all things SpaceX, and dote on my toy poodle.
Anaïs Anaïs Roussel
The questions that I am passionate about pertain to how life developed and adapted to extreme and variable environments. I am particularly interested in biomarkers, how to find them and understand them, and how we can use this knowledge in the search for life in our solar system. Before coming to Georgetown to begin my PhD, I studied engineering in biotechnologies in France and researched biomarker preservation in ancient rocks in Oman as a member of the Summons Lab at MIT.
Maggie Maggie Weng
I am a PhD student whose interests include the microbial ecology of extremophiles: understanding how life survives in extreme environments and tracing potential
avenues for habitability on other worlds. I love traveling and fieldwork, and am
always interested in looking for intersections of my work with relevant
environmental problems. When I’m not working in the lab you can find me hiking, knitting, or writing.
julie Julie Bevilacqua
I’m a research technician in the Johnson Biosignatures Lab and a recent graduate of Georgetown University, where I studied Biology of Global Health and English. I’m interested in the metabolic mechanisms for survival in harsh conditions and in the diverse applications of new sequencing technology, from research labs to the field to clinical settings. Outside the lab, I like to spend my time reading, baking, and traveling.
Chad Pozarycki
I am a research technician working in the JBL with LAB to develop standardized procedures for the preparation and extraction of field samples. I also work with NASA Goddard on Curiosity’s SAM instrument and with CIFAR on a meta-
analysis of biologically sterile, polyextreme locations on Earth. I formerly worked with the House Research Group at Penn State. I enjoy surfing, mountain biking, and hosting neighborhood jazz concerts on his front porch.
Anjali photo Anjali Britto
I’m a sophomore at Georgetown University studying Science, Technology and
International Affairs concentrating in Global Health on the pre-med track. I’m
fascinated by how studying our planet can help us understand life beyond it.
Outside the lab, I like to read, run, and draw.
IMG_3958 Olivia Gadson
I am a freshman at Georgetown University studying Biology with a concentration in Ecology, Evolution, and Behavior. I have previously aided in research that
focused on using microfossils to determine climate in the Cenomanian time
interval. I’m interested in the field paleobiology and applying the fields of geology and molecular biology to study how organisms can survive in extreme
environments. In my free time, I love to hike, read, and hang out with my cat, Nelson.
Picture1 Laura Ratliff
I am a junior at Georgetown University majoring in Biology and minoring in
Science, Technology, and International Affairs. I am curious to explore what lessons extremophiles can teach us about the limits of life on our planet and how those could apply to life elsewhere. When not in the lab, I enjoy singing in choirs,
choreographing for the tap dance club on campus, and working on a high altitude balloon payload.

Our group also has the opportunity to collaborate closely and co-supervise students with Dr. Alexandra
, a geomicrobiologist and assistant research professor at Georgetown. You can read more about her work on her Google Scholar page, or connect with her on Twitter or LinkedIn.

Lab alums include:

20170102_123157 Mia
Chloe Fishman Maryse Napoleoni Mia Vanderwilt
PastedGraphic-1 unnamed DSC00351
Matthew Fisher Sam Greenfield Angela Bai
deirdre anushree
Maya Samuels-Fair Anushree Srivastava Elena Zaikova
mark Ben Indo1 (1) deirdre
Mark Sutton Ben Johnson Deirdre Collins
savannah IMG_0354 2015-05-22 15.07.15
Savannah Fuqua Monica Soni Allee Torres