Profile: Searching for the Origins of Life

Scott Perl ’19 is nearly a mile beneath the Earth’s surface, crunching through the tunnels of the Boulby Underground Laboratory on England’s North Yorkshire coast. He’s gathering salt — 250-million-year-old salt, to be precise.

Boulby was dug into an ancient sea bed, where layers of salty sediment keep a record of the chemistry of past life. At the end of his trip, Perl will ship hundreds of pounds of briny sand back to his lab in California, where he’ll examine it for chemical signatures of ancient microbial life and to determine how long that evidence might have survived — an important factor when looking for signs of life on other planets.

His briny samples will share storage space with specimens from another extreme environment: deep-sea vents. Perl’s laboratory partner and fellow USC Dornsife Ph.D. graduate, Laurie Barge ’09, is researching fluid and minerals gathered from ocean floor vents that bubble 200 miles off the coast of southern Oregon.

The duo co-leads the Origins and Habitability Lab at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. They research how life formed on Earth to better understand how life might form on other planets. This means important lab collaborators are working “off-world.”

“We can analyze samples in our lab using instrument techniques similar to the instruments on the Mars rovers,” says Perl. Their lab can also mimic the environments of other planets, helping scientists determine the best methods for how to look for life on other worlds.

CUT FROM THE SAME CLOTH

Barge and Perl were space enthusiasts from an early age. They grew up watching Star Trek: The Next Generation and dreamed of exploring the universe. Both enrolled as undergraduates with the goal of eventually working at NASA.

As Barge began studying astronomy and astrophysics at Villanova University in Pennsylvania, she found herself increasingly drawn to the question of where life on Earth came from, and whether there might be life elsewhere in the universe.

She enrolled at USC Dornsife to pursue a Ph.D. in geological sciences after discovering the research of Ken Nealson, who was using geobiology to search for life on other planets. Nealson, now Professor Emeritus of Earth Sciences, became her doctoral adviser.

“How I worked with my adviser at USC Dornsife is how I work with my students here in the lab.”

“The department was wonderful; it really paid attention to students. I enjoyed having the freedom to explore astrobiology and biosignatures research for my thesis, and to also work at JPL part time as an intern, both of which led to my eventual postdoctoral research at JPL,” says Barge.

Perl graduated from State University of New York at Stony Brook with degrees in geology and material science, then accepted a job at JPL. He selected USC Dornsife for his geological sciences and geobiology Ph.D. program because of its flexibility for working students.

“I was looking for a department that was small enough that I could have face time with my adviser and where I wouldn’t be treated differently because I was already full time at JPL,” says Perl. “USC and JPL have a strong professional network.”

Barge and Perl met while working at JPL on the Mars Reconnaissance Orbiter mission, a spacecraft designed to study the geology and climate of Mars, and struck up a friendship. They were working as investigation scientists for instruments aboard the craft — Barge for the High Resolution Imaging Science Experiment (HiRISE) and Perl for the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). The HiRISE camera snaps images and helps find landing sites for future missions while CRISM maps mineral residue that appears where water once existed.

Barge and Perl didn’t realize at first that they were both USC Dornsife alumni or that they had attended the same astrobiology summer school in Spain, just one year apart.

“It’s funny, you can have the same life path as someone but never meet,” says Barge.

The two eventually decided to join forces and combined their individual labs into one.

“We realized there were many benefits of sharing leadership of a research group,” explains Perl.

SALT AND SEAS

Now they spend their days trying to unravel one of the most complex conundrums in astrobiology — how life began on our planet and how it can thrive on other solar system bodies. They use Earth field sites as test beds and analogous laboratory experiments to recreate rock-fluid interactions that could have led to the origin of life.

It’s a surprisingly unresolved question. Even pinpointing where life first began is hotly debated, with some researchers arguing for shallow seas while others favor the hot waters bubbling up from deep ocean vents. Perl, Barge, their students and postdocs conduct experiments that mimic various early Earth and planetary environments to understand which conditions would have been most conducive to chemistry leading to life’s origin.

They also look at samples from areas that once held life on Earth, like the sediment at Boulby, to see what traces life leaves behind. Understanding the chemical signature of past life on our planet allows scientists to look for those similar signs in the rocks they analyze on, say, Mars — or, perhaps, in the icy plumes of the ocean moons of Jupiter and Saturn.

“If life can emerge in deep-sea vents, then maybe it could have emerged on these ocean worlds as well, and future missions might be able to see signs of that organic chemistry,” explains Barge.

NASA’s rovers can touch down on Mars where water once stood and then scan for signs of life, or future missions could analyze plume material from the icy moons, with Barge and Perl comparing the mission data to what they see in the lab and in the field.

The precise point at which organic compounds acquire enough complexity to sufficiently form “life” is also still fuzzy — an important gap in our scientific knowledge that Barge hopes to fill.

“We need to better understand the boundary between life and non-life,” she says. Barge notes that planets like Mars or moons like Jupiter’s Europa or Saturn’s Enceladus could show evidence of organic compounds, yet it might be hard to determine if these compounds would qualify as once-living organisms.

LAB RESULTS

Along with solving pressing scientific questions, Perl and Barge are also defying stereotypes of scientists as lone geniuses.

“Laurie and I collaborate on everything,” Perl says. “We each have our favorite science projects but we write proposals together and serve as co-mentors to all of our students. Our work is a collective.”

They host a rotating crew of undergraduate and graduate students who assist with research projects or embark on their own science investigations. Barge and Perl credit USC Dornsife with helping inspire their lab group’s collaborative culture, which prioritizes curiosity and long-term friendship.

“How I worked with my adviser at USC Dornsife is how I work with my students here in the lab,” says Perl. “I still talk to my thesis advisers and our students return again and again. We focus not just on science experiments and research, but also on building lifelong careers.”

 —M.C.