Asteroid Sample of Record Size to Be Brought Back to Earth

On Sunday, fragments of an asteroid that hold valuable information about the early stages of our 4.5 billion-year-old solar system and the potential source of water on Earth are expected to touch down in the Utah desert.

NASA’s OSIRIS-REx mission has been in the making for more than a decade. Its goal was to retrieve a large sample of rocks and dust from a near-Earth asteroid called Bennu and bring it to our planet for study. The spacecraft successfully captured its prize in 2020, and this weekend will finally pass Earth and release the capsule containing the sample and send it down to Utah.

“This is obviously the moment we’ve all been waiting for,” said Lori Glaze, director of NASA’s Science Mission Directorate’s Planetary Science Division.

The sample helps scientists get a snapshot of what materials were present when our solar system first formed. Scientists believe that asteroids like Bennu haven’t changed much since the birth of our cosmic Neighborhood. They plan to study the recovered rocks and use the mission to inform future exploration.

“We believe that asteroids could have been the source material not only for building the rocky parts of our planet, but also for supplying the water that makes up our hydrological system,” Glaze said.

Scientists don’t know exactly how much sample is in the container, but suspect it’s the largest sample ever collected from an asteroid, weighing about 250 grams — or about as much as a hamster. This gives them more rocks to analyze than ever before.

OSIRIS-REx picked up more rocks and material than expected — so much that it jammed the spacecraft’s sample collector open and some of it leaked into space. NASA decided not to measure the sample and instead quickly stored the rocks to keep them safe.

Small risks

The spacecraft left Bennu with the sample in 2021 and has been on its way to Earth since then. On Sunday morning, OSIRIS-REx will come within 63,000 miles of Earth, when the final stage of the journey will begin – and not entirely without risk.

First, the probe releases a sample container—about the size of a tire—into space. If the container doesn’t fall as planned and gets stuck in the OSIRIS-REx spacecraft, the team will have to wait until September 2025 to try again. The spacecraft has to go around the Sun again before it gets close to Earth.

If it goes well, from there it travels down to the planet, taking about four hours to reach Earth’s atmosphere. During this time, it is not possible to control the capsule. “When we release it, it’s really just a ballistic object,” Sandy Freund, director of Lockheed Martin’s OSIRIS-REx program, said.

The container enters the atmosphere at about 27,000 miles per hour and heats up to about 5,000 degrees Fahrenheit. It has a heat shield, a critical piece of equipment designed to prevent the sample from burning – which would end the mission.

“It’s really kind of your worst-case scenario,” Freund said. “Your samples are completely gone.”

As it descends, the capsule releases a parachute to keep it stable, after which another parachute slows it down. If all goes according to plan, the capsule will land gently in Utah at 10-11 miles per hour. In the unlikely event that the parachutes don’t work and the capsule doesn’t slow down enough, the samples can still make it to the ground.

“We are prepared for a hard landing scenario,” Freund said. “It’s not ideal, but the specimens are on the ground, right? They’re not as pristine as the team would like, but they’re still here.

From there, a helicopter tows it along a cable to a clean room, where a nitrogen purge removes any impurities. It will then head to NASA’s Johnson Space Center in Houston, where the sample will be unveiled to the public in October.

A confident team

Despite the potential shortcomings, Freund says he is confident in the task. They have done several practices to prepare for the fall before Sunday. During the fall, several planes follow the container and radar in the area. The team has also improved the technology used in previous sample recovery missions.

“We’ve drawn on a lot of heritage and we’ve been very fortunate to be able to do that,” Freund said.

OSIRIS-REx could also help inform future missions to asteroids—perhaps even ones that mine these rocks for resources.

“In the future, people have talked about maybe using asteroids as resources that we could exploit,” Glaze said. “I think OSIRIS-REX’s operation near Bennu was really informative about how you would do something like that yourself.”