Testing the Waters: Astrophysicist’s Work Transports Him From the Moon to the Oceans

When astrophysicist Gerardo Dominguez tells people what he does for a living, they often ask him to point out constellations. But growing up in Los Angeles, Dominguez had few opportunities to see the stars. “The only constellation I know is maybe the Big Dipper, and that’s about it,” he says. 

Dominguez doesn’t spend his nights staring at the skies. He’s more interested in meteors and asteroids than stars. By studying the water within these space rocks, he’s solving mysteries about the solar system.

To the Moon and Back 

In his lab at California State University San Marcos, Dominguez uses isotope forensics to dust for molecular fingerprints on meteors, asteroids and other rocky materials. Isotopes are atoms of the same element that have different masses. For instance, oxygen has two common isotopes — a heavy and a light variety called oxygen-18 and oxygen-16, respectively. 

Ratios of these two oxygen atoms are used to study the history of ice formation on earth, and Dominguez is applying similar methods to explore the origins of water and ice in the solar system. Using an Isotopic Characterization Experimental (ICE) apparatus that combines infrared light and lasers, he can identify the different oxygen isotopes within his space samples.

Identifying when and how water formed within space rocks helps scientists better understand the timeline for the development of the solar system. “You can basically constrain when different components within meteorites were formed — down to a fraction of a million years,” he says. 

Given that the solar system is roughly 4.6 billion years old, “a fraction of a million years” is reasonably precise. 

Recently, Dominguez joined a global team of scientists, called the Interdisciplinary Consortium for Evaluating Volatile Origins (ICE Five-O for short), to investigate ice found near the Moon’s poles. “We’re trying to understand the origins of lunar water and also what happens to minerals when they get exposed to the solar wind and radiation,” he says.

Understanding the formation and evolution of water on the Moon may help researchers learn how water first formed on the Earth. The ICE Five-O findings will also help NASA plan future missions to the Moon. 

A Narrowly Employable Astrophysicist 

Dominguez credits books and teachers for sparking his interest in science. “In third grade, when I started to read more independently, I was really fascinated by books on volcanoes and glaciers and the solar system that I could find in the school library,” he says. “There was definitely something about those topics that captivated me.”

A few years later, Dominguez progressed from reading about earth science to conducting his own paleontological dig in the cliffs near his home. “After I found out that there were fossils from my sixth-grade science teacher, I just was fascinated by it,” he says. “I had to go out there and go find some fossils.”

But as a first generation Mexican American, he never realized his interest in geosciences could turn into a career. “I think it’s very revealing about my upbringing,” he says. “That was not something that I ever discussed, certainly not with my parents.” 

When it came time to apply for college, Dominguez wasn’t sure what major to choose. He applied to a few architecture programs because he liked to draw, but his teachers urged him to consider engineering. “People would say, ‘Well, you’re really good at math and science, so you should be an engineer,’” he says. 

He enrolled in the civil engineering program at the University of California, Berkeley, but by the end of his sophomore year, Dominguez had doubts about his career path. He realized he enjoyed his science classes much more than his engineering ones, so he transferred to the physics program. He jokes that he could have been a very successful civil engineer instead of “a more narrowly employable astrophysicist.”

Dominguez discovered atmospheric chemistry during his postdoctoral work at the University of California, San Diego. While there, he also learned about a novel imaging technique that combines atomic force microscopy with infrared lasers to characterize nanoparticles too small to be seen in a traditional microscope. He used the technique to study dust from comets and meteorites, but he suspected there were many more applications.

Getting to Hobbiton

In a departure from his extraterrestrial investigations, Dominguez’s latest project involves environmental issues here on Earth. With funding from the California Coastal Conservancy, he hopes to use the nano infrared spectroscopy he learned as a postdoc to quantify and analyze nanoplastics in the Earth’s water systems. 

Dominguez says his love of nature sparked his involvement in the project. “Only in the last maybe three years did I become aware of microplastics and then nanoplastics as an emerging problem,” he says. “Of course, in my head, I’m like, ‘Oh, wait, I have this hammer [nano infrared spectroscopy], and it would be perfect for this problem.’”

Both microplastics and nanoplastics are particles produced from the breakdown of plastic objects, but they are quite different in size. Microplastics are between 1 micrometer (or micron) and 5 millimeters across, while nanoplastics are between 1 and 1,000 nanometers. For comparison, a human hair is approximately 90 micrometers, or 90,000 nanometers, wide. 

These tiny plastic particles can slip through the filtration systems at water treatment plants and contaminate drinking water. The chemicals in the plastics also affect sea life that inadvertently ingest them. 

Eventually, Dominguez hopes to understand how microplastics turn into nanoplastics and how factors such as UV light accelerate their breakdown in water. He says a similar degradation process occurs when plastic toys are left out in the sun. “They outgas (give off vapors), and they get fragile,” he says. “There’s stuff that comes off them, residue that we just don’t think of. But there’s probably nanoplastics in there and microplastics for sure.”

For the next six months, Dominguez and his team will test the nano infrared spectroscopy technique using samples of water and polystyrene, a versatile plastic found in food packaging, surfboards, toys and electronics. 

Once they perfect the protocol, they can search for nanoplastics in seawater, ice and snow. To do so, they will need to collect water samples from different locations around the globe, including the South Pole. 

An avid “Lord of the Rings” fan, Dominguez jokes about using these sampling expeditions to fulfill his fanboy dreams. “I’m just trying to figure out a way to get to Hobbiton in New Zealand,” he says. “And to get to the South Pole, New Zealand’s kind of a stopping place on the way there.”

Nature’s Call

Dominguez claims the timing is just a coincidence, but his newfound interest in seawater coincides with his participation in another water-related activity. 

Although he loved boogieboarding as a child, he wasn’t too keen on surfing. “I tried it once when I was a teenager, and I sucked at it,” he says. “I fell over.” 

But faced with several hours of free time during a January 2020 conference in Hawaii, Dominguez opted for a surf lesson. He was instantly hooked. “I remember going out there with the surf instructor, and I stood,” he says. “I was pretty amazed at what it felt like to stand and glide on this 11-foot-long board.” He signed up for another lesson the next day.

Dominguez took a few more lessons when he returned to San Diego and got some pointers from a fellow surfer in the kinesiology department. “He told me, ‘You can take all the lessons you want in the world, but at the end of the day, you just have to go out there and try it.’”

Less than two years since that first surf lesson, Dominguez now owns five surfboards and hits the water three to four times per week. “I just love it,” he says. “It’s being out in nature, and it’s getting exercise without getting all sweaty and gross.”

A Fervor for Physics

When he’s not studying space rocks, catching waves or plotting ways to get to Hobbiton, Dominguez tries to get others interested in science. He particularly likes mentoring undergraduate students and “seeing them develop their confidence and their ability to do things independently.” 

Dominguez also enjoys giving public talks about his work. He gets excited when people want to learn about the solar system or atmospheric chemistry. And he’s always happy to answer questions — as long as no one asks him how to find Orion’s Belt.

If you are interested in learning more about physics, check out this article about the science of snack foods.