A group of scientists huddled around a television screen and anxiously watched the live coverage as an object from space streaked through Earth’s atmosphere.
This wasn’t a scene from a disaster movie, but the drama grew as the object sped closer to the Utah desert floor. Then, a parachute opened. And 2,000 miles away, Kate Freeman could breathe.
“We have a rock,” said Freeman, Evan Pugh University Professor of Geosciences, amid cheers from colleagues, students, family, and friends gathered in her State College home on a rainy Sunday morning in September.
Floating safely to the ground just west of Salt Lake City was a capsule containing rocks and dust from space—pieces of the asteroid Bennu that may carry clues about the formation of the solar system—and potentially of life on Earth.
The capsule’s return in September marked the end of a dramatic chapter for NASA’s Origins, Spectral Interpretation, Resource Identification, and Security,-Regolith Explorer, or OSIRIS-Rex, mission.
OSIRIS-Rex launched in 2016, reached Bennu in 2018, collected samples in 2020, and returned the rubble to Earth to the waiting arms of scientists like Freeman, Christopher House, professor of geosciences, and Allison Baczynski, assistant research professor of geosciences at Penn State.
The trio were among a select group of scientists picked to receive a small portion of the asteroid for study. At Penn State, they will analyze the stable isotopes in organic matter and organic molecules found in the samples.
Asteroids are like time capsules, the scientists said, preserving the earliest history of our solar system and chemical signatures of the ancestral building blocks of life. And Bennu is rich in carbon, making it an ideal specimen for this work, the researchers said.
“These are very exciting samples because they are exotic – from very far away,” Freeman said. “And we think they contain signatures from before the solar system was formed and from stuff that happened after. Untangling those two threads is something we as geoscientists are very interested in.”
A Spoonful of Asteroid
When collecting your sample requires traveling 200 million miles from Earth and landing on an object about as wide as the Empire State Building, you take what you can get.
For researchers on the OSIRIS-Rex project, that might mean receiving as little as two grams of Bennu material, about the size of a sugar packet.
That’s just fine for the Penn State researchers, who have spent parts of their careers developing ever more sensitive equipment that can do more with less material.
“Even just within the arc of my career, I’ve done a lot of instrument development work, funded by NASA, thinking ‘oh, this might be useful for a sample return someday,’” Freeman said. “And now we’re using those exact instruments for this project. That’s pretty satisfying.”
Freeman and Baczynski have developed high-precision instruments to analyze isotopes within a wide array of molecules and minerals – equipment that is housed in the Peter Deines Isotope Mass Spectrometry Laboratory in the recently renovated basement of the Deike Building.
Isotopes are atoms of the same element that differ slightly in mass due to having different numbers of neutrons in their nucleus. Certain physical or chemical processes may favor one isotope over another. Living things, for example, use a specific carbon isotope, and analyzing molecules can therefore provide clues on whether a sample’s origin is biotic or abiotic – made by living organisms or left behind by things like water or atmosphere.
With their equipment, supported by the NASA-funded Astrobiology Center for Isotopologue Research, the team can measure isotopes at specific locations within molecules, giving clues to how molecules were synthesized.
“That can tell you a little bit about if it’s biotic versus abiotic – or if we’ve acquired any sort of terrestrial contamination or not,” Baczynski said. “The isotopes will hopefully give us some insight into where this organic matter that’s present on this asteroid came from and at what point in the development of the solar system it emerged.”
Ancient Earth and Beyond
While much of her time this fall has been spent getting the laboratory ready for when Penn State receives its Bennu samples, Baczynski’s mind has not always been on asteroids and space.
As a doctoral student, she studied molecular fossils from the Bighorn Basin in Wyoming that capture the Paleocene-Eocene Thermal Maximum (PETM), a global warming event 55.5 million years ago that’s considered the best analogue for modern climate change.
Molecules left behind from the waxy coating on leaves that fell and became preserved in the rock record hold clues about the conditions ancient trees experienced—the water they took in and the carbon dioxide they breathed from the atmosphere. But the molecules were not in high enough concentrations in the rock record to measure specific biomarkers.
“This particular event I was studying was really lean in terms of organics,” Baczynski said. “We were running up against the limits of our instrumentation. So when I came to Penn State, I was working to lower the detection limits of these instruments. Because even on Earth, with terrestrial fossils, we were sample limited.”
Baczynski spent parts of four years improving the sensitivity of the equipment by two orders of magnitude, and using that tool, led research that collected the first biomarker record of the PETM from terrestrial core samples.
“And having these tools ended up being interesting to NASA and other places who were saying, ‘you know, when we send a spacecraft out and bring a sample back we are also sample limited,’” Baczynski said. “And so we thought we could bring a lot to the mission by having these analytical instruments. And clearly, they thought so too. And that’s really exciting.”
A teenager’s bedroom
Though it took the OSIRIS-REx spacecraft two years to first reach Bennu, the asteroid is actually considered a close neighbor of Earth. Passing near our planet about every six years, it is among a group of near-Earth asteroids that pose a slight risk of someday crashing into us.
“One thing that surprised me when I got involved in this project was how many of these asteroids there are out there,” Freeman said. “It kind of looks like a kid’s bedroom in adolescence. There’s a lot of stuff on the floor.”
Asteroids like Bennu may be remnants of the early solar system, which formed from the solar nebula—a hot disk of gas and dust—like hydrogen—that surrounded the early sun.
“You start to condense out from the gas, dusts and grains that ultimately build up to rocks and then into small bodies which are called planetesimals,” said Christopher House, director of Penn State’s Planetary System Science Center. “That generates what we call primitive material.”
According to NASA, scientists think Bennu’s present-day composition was already established within ten million years of the solar system’s formation—meaning it may have spent the last 4.5 billion years floating though space, not affected by the same processes happening on, for example, Earth.
“So that’s the idea—that Bennu is sort of sampling this time period in the early part of the formation of the solar system and it carries organics in it that reflect some interstellar material as well as material processed in the early history of the solar system,” Freeman said.
In conducting initial tests of the Bennu samples, NASA scientists found evidence of high carbon content and water, considered building blocks of life on Earth that could offer new clues into how these materials were distributed in the early solar system.
“When we’re studying prebiotic chemistry, we are asking where does life come from. It comes from some organic goo that had an energy source—it started with a set of processes that eventually led to life,” Freeman said.
But what were those chemicals? What was in the primordial soup to begin with and how were those ingredients shaped by their history in the solar system?
“Those are kind of a core questions,” Freeman said. “And this asteroid is a look back in time, because it was formed early in the solar system history, and then hasn't had a lot of planetary process altering it since then. And so it's a way to kind of get back to the early inventory, and grocery store that led to primordial soup.