Is there life in Europa's ocean?

If you were going to look for life elsewhere in our solar system, where would you look?

For most of us, this is a purely hypothetical question. But not for Sara Miller. Miller, who is a doctoral student in the lab of Associate Professor Britney Schmidt in Cornell’s Department of Earth and Atmospheric Sciences (EAS), has her eyes set firmly on Jupiter’s moon Europa.

There is a preponderance of evidence that life on Earth began in the oceans, so Miller and many planetary scientists believe that in our search for life outside of Earth, it would be worthwhile to explore extraterrestrial oceans as soon as we are technologically able. Beneath its global ice shell, Europa hosts one of the most promising oceans for exploration beyond Earth. Combining information beamed back to Earth from NASA’s Galileo mission in the 1990s with observations from ground-based telescopes on Earth, experts are fairly confident that Europa’s frozen shell is made of water ice, and that under the ice is an ocean of salty, liquid water surrounding the entire moon at depths of 40 to 100 miles.

Miller’s path to becoming a planetary scientist has roots in her childhood. Her grandfather was a fighter pilot and his experiences inspired Miller and her brother to dream of exploring air and space, giving way to what their family referred to as the “Miller family space race.” Miller would go into aerospace engineering while her brother went to the U.S. Air Force Academy and became a pilot. As a junior in high school Miller had an internship at NASA’s Johnson Space Center in Houston and this led her to Georgia Tech, where she completed her undergraduate and Master’s degrees in aerospace engineering.

Miller had every intention of continuing on to a Ph.D. in the same field, but then took an elective course with Georgia Tech faculty member (and Cornell alumni) Professor James Wray ’10. Wray is a planetary scientist who has been involved in several NASA missions to Mars. Miller greatly enjoyed the class. One day she went to Wray’s office hours and in the course of their conversation said how deeply she wished she had known the field of planetary science existed as she was choosing a Ph.D. program.

Wray responded by asking Miller how old she was—which was 25 at the time—and then said the words that changed her life: “If 25 is too late for you to change your mind and change your major, then God help the rest of us.”

Miller took his words to heart, was introduced to Britney Schmidt, switched majors, and in August of 2021 moved to Ithaca to continue working with Schmidt in her new lab at Cornell. Schmidt’s team studies Earth’s glaciers and ice shelves and the oceans beneath them in an effort to better understand what conditions may exist beneath Europa’s ice. Miller’s role in this work is to use her deep knowledge of fluid dynamics to mathematically model ocean circulation and ice-ocean interactions for icy moons like Europa.

“Here on Earth, the transport of heat and salt and nutrients in our oceans is critical to sustaining the biosphere—which is all the living things,” Miller said. “Ocean dynamics are a key for life on Earth. So in the search for life beyond Earth in astrobiology, understanding the fluid dynamics of how those ocean worlds like Europa work is a really interesting problem to look at.”

NASA also has its attention focused on Europa and is currently developing the Europa Clipper mission with a planned 2024 launch date. The stated goal of the mission is search for signs of habitability on Jupiter’s icy moon. The spacecraft for the Clipper mission will orbit Europa and use its cameras, spectrograph, spectrometer, magnetometer, plasma instrument, radar, surface dust analyzer, and other instruments to gather data to help answer questions about the potential for life to exist in Europa’s ocean.

The data produced by the mission will inform models and help planetary scientists paint a clearer picture of what is going on beneath the ice in Europa’s ocean. When that data starts to come in, Miller will most likely no longer be at Cornell. If the mission launches on schedule in October 2024, the Clipper will not reach its orbit just above the icy surface until April of 2030.

When Miller thinks about exactly what she’ll be doing as the Clipper swoops low over Europa and completes nearly 50 flybys, she can’t say with certainty. Her hope is that she will be working with NASA or another space agency as a project scientist---quite a goal for someone who did not know that “planetary scientist” was a career option just a few years ago.