Ehlmann was born in
Southern California, where her father, Bryon Ehlmann, was an assistant professor of
Computer science at
Chapman University. The family then relocated to
Tallahassee, Florida, where Bryon was a professor at
Florida A&M University and
Florida State University. Ehlmann graduated from
James S. Rickards High School with an
International Baccalaureate Diploma in 2000, where she was awarded the
Fred Biletnikoff Award. They then relocated to
Edwardsville, Illinois, near Bryon's hometown of
St. Charles, Missouri, where he was a professor at
Southern Illinois University Edwardsville. She graduated with a
Bachelor of Arts and Science in 2004. She then attended the
University of Oxford as a
Rhodes Scholar beginning in 2004. There, she received two
Master of Science degrees, one in Environmental Change and Management under the mentorship of John Boardman, awarded in 2005, and the other in
Geography under the mentorship of
Heather Viles, awarded in 2007. While at Oxford, she contributed to the analysis of
remote sensing data to help evaluate safe landing sites for the
Mars Exploration Rover in a 2005 study. Her Geography thesis was entitled "Developing quantitative techniques for evaluating rock breakdown morphology: a case study of basalt boulders in the
Channelled Scablands, Washington, USA." Ehlmann then returned to the United States to attend
Brown University for a Master of Science degree and a
Doctor of Philosophy (PhD) in
Geological Sciences in the research group of
John F. Mustard. During her doctoral career, her focus shifted to studying
Mars, utilizing orbital spectral data from the
Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), a visible-infrared spectrometer aboard the
Mars Reconnaissance Orbiter that takes measurements from the surface and atmosphere of Mars. CRISM is used to find the signature spectral signatures of different minerals to understand what minerals are present on Mars and form hypotheses on how different geological processes have shaped the planet over the course of its history. Using CRISM data, Ehlmann became the first to identify
carbonate-bearing rocks on Mars, the presence of which suggests that water present on Mars when these rocks formed was neutral to alkaline. She also discovered evidence for the presence of a
methane-producing mineral called
serpentine on Mars. The discovery could be a clue of past life on Mars, as serpentine arises from a mineral called
olivine in a hydrothermal process that could serve as an energy source for methane-producing microbes. Her dissertation, published in 2010 and entitled "Early Mars Environments Revealed Through Near-Infrared Spectroscopy of Alteration Minerals," documented her investigation of aqueous processes that occurred on ancient Mars during the earliest epoch of Martian history: the
Noachian (>3.7 Ga). The work was aimed, in part, at better understanding the changing habitability of Mars over time, as well as understanding how aqueous environments have evolved on Mars. Her dissertation received Brown University's Joukowsky award for the outstanding PhD dissertation. In 2024, Ehlmann received an honorary
Doctor of Science from Washington University. == Research and post-doctoral career ==