Analyzing Bennu

As part of their work with the samples, Milliken’s team is using reflectance spectroscopy, a technique that analyzes the light reflected at visible wavelengths of light, as well as near- and mid-infrared wavelengths that are longer than what the human eye can see. The key objectives are to better understand what appear to be two distinct types of rock on Bennu and to better grasp the material’s complex chemical history.

Researchers at Brown from the lab of Yongsong Huang, a professor of Earth, environmental and planetary sciences, will also be analyzing samples from Bennu when an upcoming shipment of fragments arrives from NASA. Huang’s team of organic geochemists plans to shine a spotlight on the organic chemicals present in Bennu samples using a series of newly developed methods. They plan to analyze a slew of volatile or highly volatile organic compounds such as methane, ammonia, formic acid, acetic acid, and small aldehydes and ketones.

“These compounds are the fundamental ingredients for synthesizing more sophisticated biomolecules such as amino acids and nuclear bases, which are also present in Bennu,” Huang said. “The analyses can provide key information for cosmic organic synthesis and fill in some of the missing puzzle pieces on how organic life may have started on Earth.”

So far, the first published studies of Bennu samples that Brown researchers were involved with, show that the asteroid contains water-bearing minerals, carbon, nitrogen, phosphorous and organic compounds. Now, researchers want to pinpoint and break down that data more thoroughly, quantifying the diversity of its composition.

The Bennu samples RELAB is analyzing look like ground pieces of charcoal to the naked eye and are kept in a specialized sample preparation box under nitrogen so that they will not be altered by oxidation, water vapor or contaminated by dust. 

“Our clean room is designed in a specific way,” said Takahiro Hiroi, a senior research scientist at RELAB. “The pristine samples must be kept dry enough to prevent water absorption but should not be too dry to cause static electricity. The temperature is just right for us to be comfortable enough but stable for the samples.”

Involvement in OSIRIS-REx sample analysis taps into the Department of Earth, Environmental and Planetary Sciences’ history of handling samples from planetary missions dating back to Apollo missions to the Moon. In September 2021, researchers at RELAB were among the first in the U.S. to examine samples from Ryugu, another near-Earth asteroid, helping show how the outermost surface of the asteroid lost some of its water.

“It's really exciting to be able to continue this long tradition of working with very sensitive materials,” Milliken said. “It speaks very highly of our department, our research environment and how our faculty have been trusted the past 35 plus years with these types of measurements.”

As an asteroid, Bennu is potentially hazardous because every six years it crosses Earth’s orbital path. In fact, scientists calculate a 1 in 2,700 in chance that Bennu could hit Earth in the year 2182. That is part of the reason NASA chose Bennu to sample and adds to the reverence planetary scientists have for this asteroid which is a fragment of a bigger asteroid.

“By studying Bennu, we're actually studying the excavated interior of its larger parent body, which is a really fascinating way to peer inside asteroids to see how they work,” said Cody Schultz, a postdoctoral researcher in the lab.

For Schultz, who worked in the lab while earning his Ph.D at Brown, the unique experience has been particularly powerful.

“Space exploration is one of the most exciting human endeavors and is what initially inspired me to study planetary science, so having the opportunity to be a part of the OSIRIS-REx team and work with these samples has been an extremely rewarding experience,” Schultz said. “Being able to say as a graduate student that you've worked with meteorites, studied asteroids and analyzed returned samples all within the course of your dissertation is pretty rare and will help serve as a launchpad for more exciting asteroid science to come.”