Scientists have predicted that Asteroid Bennu, which passes by Earth every six years in its orbit, has a 1 in 2700 chance of striking Earth in 2182.
Bennu has been on NASA’s radar for 25 years, first discovered by their Lincoln Near-Earth Asteroid Research (LINEAR) survey in 1999. Bennu is only slightly taller than the Empire States Building, weighing a staggering 78 billion kilograms and averaging 490 meters in diameter. Bennu’s elliptical orbit intersects with Earth every six years and we’ve already had 3 near misses. The 1 in 2700 chance that it might be pulled out of its orbit and strike Earth in September 2182 has prompted NASA to classify it as a “hazardous near Earth object”.
OSIRIS-REx
While NASA has been keeping a close eye on Bennu, especially when it comes around every six years, there is always more to learn. In 2016, NASA launched a spacecraft, the Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer or OSIRIS-REx, to the asteroid which has since photographed optical images of Bennu, mapped the surface and transmitted radio tracking signals that have allowed NASA to track its precise location and orbital path. OSIRIS-REx has also tailed Bennu to confirm whether scientists’ predictions about its orbit are accurate. Another important goal for the spacecraft is to learn how much the Yarkovsky effect, a heat nudge that alters the asteroid’s orbital course, will push the asteroid closer to Earth.
Obtaining a sample
As important as gathering all that information is, OSIRIS-REx’s greatest task was to obtain a sample from the asteroid. The Explorer accomplished that mission in October 2020. The Explorer made brief contact with the Asteroid to obtain 250 grams of the rock sample, four times the minimum required sample. While the sample is critical to understanding Bennu’s trajectory and ways to prevent a collision, the sample is precious for other, perhaps more exciting, reasons. Bennu is an asteroid born during the early days of our solar system, maybe as old as 2 billion years – which in the geologic time scale is still relatively recent. Scientists believe Bennu is composed of some of the building blocks that formed our solar system, with the potential to answer our most burning questions about the birth of the solar system, including where the organic molecules essential for life came from.
“This is pure untainted material revealing early solar system secrets. A longshot discovery would be finding biological molecules or even precursor molecules for life” explained Hakeem Oluseyi, a distinguished astrophysicist, cosmologist and inventor.
Cracking open the Treasure Trove
OSIRIS-REx has fulfilled its mission. The capsule containing the precious sample returned to Earth on Sep 24, 2023 parachuting down in the Department of Defense’s Utah Test and Training Range . The sample capsule was released from the Explorer to plummet through the atmosphere at around 2700 mph as a fiery streak before two parachutes slowed it down to a gentle 11 mph at touchdown. The capsule was recovered and transported to the Johnson Space Center in Houston, TX. On September 26, the capsule was opened in a curation facility that preserved the purity of the sample. Interestingly, when the canister was opened, scientists discovered dust on the canister that they had not anticipated being there. As was revealed in a Twitter post by NASA Astromaterials, “Scientists gasped as the lid was lifted from the OSIRIS-REx asteroid sample return canister, showing dark powder and sand-sized particles on the inside of the lid and base”. The dust has been sent to other facilities for analysis but no results will be revealed for at least a month.
So what will the sample actually reveal? Will the mysteries of the origins of our solar system finally unravel? Might we avoid a possible asteroid collision looming 159 years away? It is still too soon to tell. NASA has set 70% of the sample aside for future generations to study using more sophisticated technology and is still awaiting detailed analysis reports. But these discoveries aside, this mission was yet another historical accomplishment for NASA and mankind. We have come half a century past the moon landing, and we’ve collected samples from the other side of the solar system. We’ve advanced further into the Final Frontier than we’ve ever been and we’ve found more new questions than we have answers. And we are perhaps one step closer to unlocking the secrets of the origins of the Solar System.
