Image showing OSISRIS-Rex getting ready to touch the surface of Bennu. (Image Credit: NASA/Goddard/University of Arizona)
NASA's OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) spacecraft finally returned a capsule of the Bennu asteroid sample to Earth on September 24, marking the first time the space agency achieved a feat. The regolith sample could give researchers better insight into the solar system's origins. OSIRIS-REx launched on September 8, 2016, arriving at Bennu on December 3, 2018. It then collected the sample on October 20, 2020, before heading back to Earth on May 10, 2021. In total, the spacecraft traveled 3.86 billion miles. The spacecraft, under a new mission name: OSIRIS-APEX (Origins, Spectral Interpretation, Resource Identification, Security-APophis Explorer), is now heading to the Apophis asteroid.
The capsule doesn't have any onboard location sensors, so aircraft, radar, optical, and ground-based instruments tracked its descent. For example, infrared equipment tracked the capsule's heat signature sourced from the interaction with the Earth's atmosphere. The capsule's heat shield kept the sample safe from damage during reentry by regulating the temperature inside, ensuring the temperature stayed below 167 °F. After landing on the ground, the radar instruments provided coordinates for the recovery team to pick it up.
The sample capsule safely touched down on September 24, 2023, and the atmospheric heat didn't damage it during reentry. (Image Credit: NASA/Keegan Barber)
OSIRIS-REx dropped off the capsule 63,000 miles above the Earth's surface, entering the atmosphere at 27,650 mph. It took fifteen minutes for the capsule to touch down in the Defense Department's Utah Test and Training Range. Recovery and research teams, transported via four helicopters, assessed the capsule, ensuring it didn't sustain damage on the descent, and verified it hadn't been breached while landing. After determining it was safe, the recovery teams retrieved the capsule. Wearing protective gloves and masks, they ensured the capsule cooled down before touching it since it reached 5,000°F while reentering the atmosphere.
The capsule was transported in a cargo net via helicopter to a nearby clean room, where the curation team purged it with nitrogen gas, keeping the Earth's environment out of the sample canister. Additionally, the recovery team assesses the footage during the capsule's descent to see if the drogue parachute deployed on time since they didn't have any visuals when it was released.
The left Image shows the collector head hovering above the SRC after the TAGSAM arm moved it into position for capture. The right Image shows the collector head secured on the SRC's capture ring. (Image Credit: NASA/Goddard/University of Arizona/Lockheed Martin)
On October 20, 2020, the OSIRIS-REx spacecraft de-orbited Bennu by firing its thrusters. Afterward, it extended the 11-foot sampling arm's shoulder, elbow, and wrist and moved across the asteroid as it descended 805 meters toward the surface. OSIRIS-REx finally touched the surface after autonomously descending for four hours to a 26-foot-wide region on Bennu, avoiding boulders that could've tipped the spacecraft or sample head and hindered the sample collection mission. At this point, it began the Touch-And-Go (TAG) maneuver and burst out nitrogen gas, stirring up dust and pebbles that the sample-collection head captured. OSIRIS-REx's thrusters then fired, allowing the spacecraft to back away from the asteroid.
Images sent to the mission team two days later revealed the spacecraft captured more material (an estimated 8.8 ounces/250 grams) than expected for this mission's objective. Then, the Sample Return Capsule (SRC) and sample stowage procedure began on October 24, lasting for two days. So, the team assessed the images and telemetry data to verify the operation went well. Doing so also meant that the team needed to work with a time delay of more than 18.5 minutes since the signals had to travel 205 million miles back and forth.
During this process, the team observed the Touch-And-Go Acquisition Mechanism's (TAGSAM) wrist alignment, confirming the collector head was correctly stored in the SRC. They also looked at the images, observing material leaking from the collector head to verify particles wouldn't affect the stowage process. Although the StowCam images revealed some particles leaked out during stowage, the team remained certain that the head still contained sufficient regolith. They determined that leakage occurred because a mylar flap purposed to keep the sample in the head was wedged open by larger pebbles. Sample pieces stopped leaking when the head was secured in the SRC.
On October 27, the TAGSAM arm put the collector head inside the SRC. The next day, the OSISRIS-Rex team performed a backout check to confirm the collector head secured into the capsule. That involved instructing the TAGSAM to arm to back out of the capsule, a process that tugged on the collector head and made sure the latches secured. After the backout check, the TAGASM arm's two mechanical parts, which connect the sampler head to the arm, disconnected. OSIRIS-REx also cut the tube delivering the nitrogen gas, which stirred up the regolith through the TAGSAM head and separated the collector head from the TAGSAM arm.
Later that night, OSIRIS-REx received commands from the team to close the Sample Return Capsule. It did this by closing the lid and securing two internal latches, concluding the stowage process and the most difficult phase of this mission. Then, on May 10, 2021, OSISRIS-Rex fired its main engines at full throttle for seven minutes. That thrust the spacecraft away from Bennu at 600 mph, heading back to Earth on a 2.5-year journey.
Levi Hanish and Michael Kaye removed the sample return canister's lid. (Image Credit: NASA/Robert Markowiz)
On September 26, NASA researchers opened the canister's outer lid after the spacecraft landed in the northern Utah desert. "Scientists gasped as the lid was lifted from the asteroid sample return canister, showing dark powder and sand-sized particles on the inside of the lid and base," NASA's Astromaterials Research and Exploration Science (ARES) division wrote in a post on X.
Scientists plan to study this sample for decades, hoping that it leads to a better understanding of the solar system's formation and how carbon-rich asteroids seeded the Earth with the building blocks of life. However, the ARES team isn't ready to tackle that because the regolith sample hasn't been accessed. That will take time since the TAGSAM arm needs to be disassembled first. Over the next two years, researchers will analyze the regolith in a clean room at the Johnson Space Center. Worldwide laboratories, like the Canadian Space Agency and Japanese Aerospace Exploration Agency, will also receive parts of the sample. Approximately 70% of the sample will remain in storage for future generations.
"There is a very high level of focus from the team — the sample will be revealed with an amazing amount of precision to accommodate delicate hardware removal so as not to come into contact with the sample inside," JSC officials wrote in a blog post.
On October 11 (11 a.m.), NASA also plans to reveal the Bennu asteroid sample, sharing analysis of fine-grained material during a webcast event. That analysis is expected to find minerals and chemicals in the sample.
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