Follow Us Add us as a preferred source on Google Newsletter Subscribe to our newsletter On September 30, NASA formally concluded OSIRIS-REx, the historic first U.S. mission to extract a pristine piece of an asteroid and return it safely to Earth. The van-sized OSIRIS-REx spacecraft, short for Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, visited and sampled Bennu, an ancient space rock containing pristine remains from the dawn of our solar system more than 4.5 billion years ago. Among those cosmic relics are raw organic building blocks, the kind that may have seeded life on Earth. “I’ve known for a long time that this day would come, but it’s still hard to see it coming,” said OSIRIS-REx principal investigator Dante Lauretta, who works at the University of Arizona, in a post on LinkedIn. “I feel enormous pride in what we achieved together and real sadness that this journey has come to an end.” For the mission team, the farewell capped a decade of high-risk engineering, on-the-fly problem-solving and tough times that ultimately delivered to Earth the largest asteroid sample ever collected in space, one that held secrets from the early solar system. Long before launch, the team faced obstacles that nearly derailed the effort (mainly, two rejections from NASA) before finally securing the green prize. light for the billion-dollar New Frontiers Program project in 2011. When OSIRIS-REx launched on September 8, 2016, on a two-year journey through the inner solar system, Bennu was little more than a point of light in telescopes. Scientists expected the asteroid’s surface to be a smooth, sandy sphere where OSIRIS-REx could land safely. However, to their surprise, when the probe reached the asteroid in late 2018, it revealed that Bennu was a treacherous, loose amalgam of jagged rocks. “Our expectations about the asteroid’s surface were completely wrong,” Lauretta said in an Oct. 7 statement from the University of Arizona. “There was no obvious place to collect a sample.” When OSIRIS-REx landed in a small crater called Nightingale, Bennu offered so little structural resistance that scientists said its surface reacted more like a fluid than a hard, rocky shell. The spacecraft’s sampling head plunged directly into the asteroid, stopping after digging 20 inches (51 centimeters) deep by firing its thrusters at the right time to zoom away, precious sample in hand. NASA’s OSIRIS-REx spacecraft captured this series of images of asteroid Bennu on April 14, 2020, during the first rehearsal of the mission’s sample collection event. The actual sample recovery was very similar to what this looks like. (Image credit: NASA/Goddard/University of Arizona) Then came another exciting moment: The lid of the sample collector got stuck in a partially open position because too much material was collected, allowing fragments of the precious cargo to escape. In a race against time to avoid further losses, the mission team quickly stowed the sampler head directly inside the return capsule, securing the cosmic treasure for its return trip to Earth. Even the final return to Earth, on September 24, 2023, kept the team on edge: a parachute failed to deploy correctly during re-entry, forcing a tense but ultimately safe landing in the Utah desert. What to read next “Successful exploration missions are not those that avoid surprises; they are those that are deliberately designed to accommodate them,” Lauretta said in the statement, quoting a line from the mission’s final report to NASA. “That certainly describes OSIRIS-REx,” he said. “Time and time again, the mission presented us with circumstances we did not expect, and time and time again, this team found a way forward.” The mission’s triumphs began long before the samples reached Earth. For example, the probe set a Guinness World Record when it slid into orbit around the 490-meter (1,610-foot) wide Bennu, which became the smallest object ever orbited by a spacecraft. The scientific bounty that followed included remote sensing work that confirmed that Bennu’s surface is coated in carbon-containing compounds. Those observations also revealed that Bennu was once part of a much larger, water-rich parent asteroid that shattered in a catastrophic collision in the main asteroid belt between Mars and Jupiter. The returned sample, which weighs 4.29 ounces (121.6 grams) here on Earth, more than twice what the mission required, continues to excite and occupy scientists. A wave of research papers, now numbering more than 200, continues to piece together the composition and history of the ancient space rock. Among other findings, pristine material from Bennu has revealed amino acids and sugars that, on Earth, are essential for life, along with a history of exposure to liquid water that could have served as a “broth” for these compounds to interact. More discoveries are likely. Most of the returned Bennu sample is being preserved for future generations of scientists, who will study it “with questions and instruments we cannot yet anticipate,” Lauretta said in the statement. Although its OSIRIS-REx chapter is closed, the spacecraft itself is far from retired. Renamed OSIRIS-APEX (OSIRIS-APophis EXplorer), the probe is using its remaining propellant to head toward Apophis, another near-Earth asteroid and a different type of space rock from Bennu. It is scheduled to arrive in 2029.
