Asteroid Bennu could impact Earth 0:44

(CNN) -- When the OSIRIS-REx spacecraft passes close to Earth on Sunday, it is expected to deliver a rare cosmic gift: a pristine sample collected from Bennu, a near-planet asteroid.

If all goes according to plan, the spacecraft will launch from space a capsule containing about 250 grams of rocks and soil from the asteroid toward a landing zone in the Utah desert.

NASA will livestream the sample delivery starting at 10 a.m. Miami time on Sunday. The capsule is expected to enter Earth's atmosphere at 10:42 a.m. Miami time, traveling at about 44,498 km/h. It will land in Utah about 13 minutes later.

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After releasing the capsule, OSIRIS-REx will continue its journey through the Solar System to observe in detail another asteroid called Apophis.

Studying the sample can help scientists understand key details about the origins of our solar system, as asteroids are the "remnants" of those early days 4.500 billion years ago. But the sample may also provide information about Bennu, which has the potential to collide with Earth in the future.


NASA has been preparing for years to return to Earth the first asteroid sample collected in space. Here are the milestones of the mission to date and what lies ahead.

The spacecraft captured detailed images of the asteroid's surface.
(Credit: NASA/Goddard/University of Arizona)

The cosmic journey of a spaceship

OSIRIS-REx, an acronym for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, has made a great journey in the last seven years. Launched from Cape Canaveral in 2016, NASA's spacecraft reached Bennu's orbit in December 2018.

OSIRIS-REx, the first U.S. mission sent to a near-Earth asteroid, made history several times. It made the closest orbit of a spacecraft to a planetary body (and Bennu became the smallest object ever orbited by a spacecraft).

OSIRIS-REx inspected the asteroid in its entirety to determine the best location to collect a sample. Bennu measures approximately 500 meters across and is composed of rocks held together by gravity.

The views of Bennu provided by the spacecraft allowed the mission team to gain unprecedented information about the asteroid, which included the discovery of ice locked up in Bennu's rocks and of carbon in a form largely associated with biology. The team also witnessed the release into space of particles from the asteroid.

The spacecraft got closer and closer to the asteroid until, on October 20, 2020, it carried out the historic TAG (Touch-and-Go) sample collection mission.

Throughout the mission, problems arose that threatened its success, such as the spacecraft's sample collection head picking up so much material that the container could not be properly sealed, causing valuable material from the asteroid to leak into space.

During the historic collection event, the sampling head of the OSIRIS-REx spacecraft plunged 0.5 meters into the asteroid's surface. Apparently, Bennu's exterior is made up of loose particles that are not securely bonded together, judging by what happened while the spacecraft was collecting a sample. If the spacecraft hadn't fired its propellant to back up after its rapid collection of dust and rocks, it could have sunk directly into the asteroid.

That's when the mission team discovered that the asteroid's surface is similar to a pit of plastic balls.

Illustration of the OSIRIS-REx spacecraft descending towards the rocky surface of asteroid Bennu.
(Credit: NASA/Goddard/University of Arizona)

The OSIRIS-REx team was able to meet and overcome these challenges, and the spacecraft is expected to return the largest sample collected by a NASA mission since Apollo astronauts brought back moon rocks decades ago.

The team was also able to arrange a final flyby of Bennu in April 2021, which gave them a chance to see how OSIRIS-REx disturbed and altered the asteroid's surface during sample collection. The before-and-after photos showed some intriguing differences created by sample collection and firing the spacecraft's thrusters after it moved away from the asteroid, including the movement and rearrangement of large rocks on the asteroid's surface.

Return to Earth

Since saying goodbye to Bennu in May 2021, OSIRIS-REx has been on a journey back to Earth, circling the Sun twice so it could pass by our planet at the right time to drop off the asteroid sample.

NASA and Lockheed Martin Space have spent much of this year rehearsing every step of the sample recovery process.

If the spacecraft's trajectory goes well, the sample capsule is expected to detach from OSIRIS-REx 102,000 kilometers from Earth early Sunday. Since departing Bennu, the spacecraft has performed numerous maneuvers and fired its thrusters to pass by Earth at the right time to release the capsule. The capsule will land in an area 58 kilometers by 14 kilometers at the Department of Defense's Utah Test and Training Range.

Parachutes will deploy to slow the capsule to a soft landing at 17.7 km/h and teams will be prepared to retrieve the capsule once it is safe to do so, said Sandra Freund, OSIRIS-REx program manager at Lockheed Martin Space, which partnered with NASA to build the spacecraft, provide flight operations and help recover the capsule.

A helicopter will transport the sample in a cargo net and deliver it to a temporary clean room set up at the firing range in June. There, a team will prepare the sample container for transport on a C-17 aircraft to NASA's Johnson Space Center in Houston on Monday. Details about the sample will be revealed via a NASA broadcast from Johnson on Oct. 11.

Scientists will analyze rocks and soil over the next two years in a dedicated cleanroom inside the Johnson Space Center.

It is crucial to better understand the population of near-Earth asteroids, such as Bennu, that could collide with our planet. A better understanding of their composition and orbits is key to predicting which asteroids may come closest to Earth and when, as well as developing methods to deflect them.

The sample will be divided and sent to laboratories around the world, including OSIRIS-REx mission partners at the Canadian Space Agency and the Japan Aerospace Exploration Agency. About 70% of the sample will remain intact in the warehouse so that future generations, with better technology, can learn even more than is now possible.

The exhibition will reveal information about the formation and history of our solar system, as well as the role of asteroids in the development of habitable planets like Earth. Scientists believe that carbonaceous asteroids like Bennu slammed into Earth early in their formation, contributing elements such as water.

The sample is expected to land at the Department of Defense Test and Training Range in Utah, where recovery teams have been training for months.
(Credit: Keegan Barber/NASA)

"We're looking for clues that explain why Earth is a habitable world, this rare gem of outer space that has oceans and a protective atmosphere," explains Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona in Tucson.

"We think all those materials were brought by these carbon-rich asteroids very early in the formation of our planetary system. We think we're bringing back that kind of material, literally, maybe representatives of the seeds of life that these asteroids delivered early on our planet and that led to this amazing biosphere, to biological evolution and to us being here today."

asteroid Bennu