Wwhat would it be like to hold a piece of space in your hand? Some lucky scientists will soon find out when NASA’s OSIRIS-REx spacecraft (shorthand for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) returns from its seven-year mission. The probe will drop from a canister containing about a cup of pebbles and dust from the surface of the near-Earth asteroid Bennu. “Bennu is a time capsule of the early solar system and we are cracking it open,” said Amy Hofmann, an isotope geochemist at NASA’s Jet Propulsion Laboratory who is a co-investigator on the mission. “We can be the first to see what’s inside. I get goosebumps when I talk about it.”
Hofmann is one of approximately 200 scientists who will receive parts of the payload brought back by OSIRIS-REx. On Sept. 24, the probe will release its sample return capsule, which will fly through Earth’s atmosphere and make a parachute landing at the Department of Defense’s Utah Test and Training Range. If all goes well, salvage teams will helicopter it into a portable cleanroom to remove the heat shield and backing, then fly it to a specially prepared facility at the Johnson Space Center in Houston. Scientists there will carefully open the inner container and handle it in a glove box to keep out all contaminants, to retrieve some of the only pristine bits of asteroid ever to reach Earth’s surface. (Meteorites are great too, but their unprotected burning through our atmosphere changes them.)
The samples will reveal the state of the solar system when it first formed, including what amino acids and other chemical compounds important to biology were present. “The ‘O’ in ‘OSIRIS-REx’ really stands for the origin of life,” said Dante S. Lauretta of the University of Arizona, the mission’s principal investigator. “We want to understand the role these carbon-rich asteroids played in bringing the precursors of life to Earth.”
OSIRIS-REx was launched in 2016 and arrived in Bennu in 2018. It spent two years near the space rock, taking measurements with its onboard cameras, spectrometers and other instruments. Those scans revealed a lot about Bennu, including that it resembles a pile of loosely bound debris more than a solid object and that it contains hydrous minerals. But the real reward is the monsters. “We have access to cutting-edge technology here on Earth,” said study co-author Michelle Thompson, a planetary scientist at Purdue University. “Having time, having this huge team and having the ability to do coordinated analyses, to look at the same sample with multiple different techniques – there’s really nothing that can replace that. The return of samples is a cornerstone of planetary science.”
In October 2020, the spacecraft made a close approach to the asteroid and touched the surface briefly with its Touch-and-Go Sample Acquisition Mechanism (TAGSAM), a robotic arm that fired a burst of nitrogen gas to stir up dust and rock. then piped to its collection head. “It’s like an air filter, except we brought the air,” says Lauretta. Photos taken during the collection process suggest that the mission scooped up a lot of material. Some extra bits of sample even stuck to the outside of the TAGSAM.
After scientists reopen the TAGSAM to Earth, a quarter of the catch will go to the OSIRIS-REx team, which will distribute it from the Johnson Space Center to laboratories around the world. Four percent of the sample will go to Canada, a contributor to the mission, and at least 0.5 percent will go to Japan, which carried out the two Hayabusa missions that returned the world’s first asteroid samples in 2010 and 2020. But 70 percent of the returned items will not be touched by anyone, at least for now. “As with Apollo, we want to save the vast majority of samples for future scientists,” said University of Arizona planetary scientist Andrew Ryan, leader of the OSIRIS-REx Sample Physical and Thermal Analysis Working Group. “We’re going to have new questions, there’s going to be future tools, and we want to make sure we haven’t burned out the whole sample.”
Even the first scientific findings should significantly increase our knowledge of asteroids like Bennu. Ryan’s team will measure how much heat the material conducts, how much space there is between the particles in each grain and how strong the force is that holds the pieces together. By comparing their findings to estimates researchers made when the spacecraft orbited Bennu, they can better characterize other asteroids based on distant measurements — a potentially critical ability if we need to deflect an Earth-bound rock in the future. .
Hofmann will use a special kind of mass spectrometer called an Orbitrap to identify specific organic molecules with different isotopic compositions in her samples and compare their amounts. For example, measuring the extent to which multiple carbon-13 atoms (a rare, stable form of carbon with an extra neutron) replace carbon-12 (the most abundant form of carbon) in a given molecule can tell researchers about the temperature when the connection formed. “These measurements weren’t even possible when OSIRIS-REx was first proposed,” says Hofmann. “It’s forensics for planetary science.”
Thompson will use electron microscopes to study how Bennu has been weathered over time by impacts from other space rocks and by energetic particles streaming off the sun. These measurements, combined with the findings of other planned experiments for the samples, aim to provide a comprehensive picture of the state of our early solar system and how it became what it is today. “The questions we are going to answer are very diverse,” she says. “[They cover] everything from understanding and characterizing the building blocks of the solar system to looking at the material’s physical characteristics. We will emerge from this mission with a totally revolutionary understanding of these types of bodies. Everyone should be very excited.”
![The timeline of the OSIRIS-REx mission begins with the launch date of September 8, 2016 and ends with an expected arrival of asteroid Apophis in 2029. Key dates are highlighted, including October 20, 2022 (Bennu sample collection) and September 24, 2023 (sample capsule is expected to be delivered to Earth).](https://static.scientificamerican.com/sciam/assets/Image/2023/saw070823Mosk31A_d(1).png)
![A series of discrete frames illustrates how OSIRIS-REx approached Bennu, briefly touched the asteroid and collected surface material with a cylindrical head on a robotic arm, took off, and then stored the material in a sample return capsule.](https://static.scientificamerican.com/sciam/assets/Image/2023/saw070823Mosk31B_d.png)
![A series of discrete frames illustrates how the asteroid material is expected to be delivered to Earth. OSIRIS-REx will release its sample return capsule on Sept. 24 and then move into orbit around the sun. The capsule will fall, two parachutes slowing it down to 4.6 meters per second for a soft land at the Utah Test and Training Range.](https://static.scientificamerican.com/sciam/assets/Image/2023/saw070823Mosk31C_d.png)