‘Science on Saturday’ lecture brings students along a cosmic treasure hunt to find stardust in meteorites

Lawrence Livermore National Laboratory’s (LLNL’s) educational outreach program Science on Saturday kicked off its 2026 program with an impactful lecture on meteorites and cosmochemistry. Held on Saturday mornings at the Mertes Center for the Arts in Las Positas College, the annual series offers local students and other community members a glimpse into the life and work of LLNL researchers.

In a February 7 presentation titled “Cosmic Treasure Hunt: Finding Stardust in Meteorites,” LLNL scientist Emilie Dunham and Granada High School teacher Tom Shefler teamed up to deliver an interactive lecture on cosmochemistry, a field that sits at the intersection between geology, chemistry, and astrophysics.

The presentation opened with a foundational question: “What is a meteorite?” From there, Emilie traced the origin of meteorite material from explosive stars and explained how meteorites preserve physical evidence of those cosmic events. She brought several notable meteorite fragments to show, including a piece of the Chelyabinsk meteorite, which fell in Russia in 2013 and was named for the town where it landed.

Tom gave the first of two demonstrations to connect cosmic element formation to everyday objects. He and Emilie arranged a set of familiar household objects on a table to show the source of the elements around us: a balloon filled with helium, a coal briquette representing carbon, and metallic items such as iron pills and silverware. Tom explained that lighter elements like hydrogen and helium were forged in the Big Bang, whereas carbon, calcium, potassium, and iron were made in the cores of stars. Lastly, heavier metals such as copper, zinc, silver, and gold were formed during star explosions.

After summarizing where elements originate from, Tom then explained how scientists infer their histories. The second demonstration illustrated some basic atomic science cosmochemists use to estimate how, when, and where different meteorite materials form and evolve. Using a chocolate sandwich cookie as a model, Tom described the protons and neutrons make up an atom’s nucleus, and how the nucleus is surrounded by electrons. “Isotopes of an element are the same element with different numbers of neutrons. In the cookie model, the ‘thin-stuffed’ and the ‘thick-stuffed’ cookies are still the same flavor as the normal cookie—science is delicious!” he explained. He held up each version of the cookie, visually reinforcing the idea that isotopes share an identity but differ in mass.

These small differences are not just significant in differentiating cookies, but are also one of the main clues that cosmochemists look for to study the origin and age of meteorites. Cosmochemists typically analyze meteorite samples to extract isotopic fingerprints, determine their structure, and identify their elemental composition.

Tom tied the concept back to our own origin: “The hydrogen atoms inside us are almost 14 billion years old, as old as the universe, and the carbon atoms that makes up our bodies originated in stars,” he said. “That means the atoms in our bodies are older than the solar system.”

Emilie then explained how these cosmic timelines are determined in practice, using the array of microanalytical techniques available to her. “Every instrument that I need to study stardust samples is here at LLNL,” Emilie said. “And the people who run the facilities and who are excited to collaborate with me make the work possible and fun.”

Emilie focused on three different types of mass spectrometers: a towering secondary ion mass spectrometer (SIMS), a room filled by a resonance ionization mass spectrometer (RIMS), and a sofa-sized noble gas mass spectrometer (NG-MS). Mass spectrometers are instruments that identify and measure atoms or molecules by turning them into charged particles and then separating them by mass-to-charge ratio. Scientists can then determine what a sample is made of, and the relative amounts of different isotopes.

The lecture drew to a close with an interactive storyboard quiz about the life of a stardust grain and an audience Q&A session.

After fielding questions from the audience, Emilie invited students, parents and other audience members to see and touch the meteorites that she had held up during the lecture. “People are always amazed that they can hold a piece of the Moon and Mars,” she shares.

Emilie, a first-time Science on Saturday presenter, felt honored for the opportunity to share her research experience. “The collective atmosphere we created mirrored the curiosity and awe that I felt,” she says. “Sharing my research with the public feels like a big part of my purpose in doing that research, it’s very inspiring.”

View past lectures on LLNL’s Science on Saturday YouTube channel

—Grace Jeng