A brown and white spacecraft that swooped across the solar system and stayed on an asteroid for seven years has returned to Earth. And it’s brought back a space rock memento that scientists can’t wait to study.
They watched the pod speed through Earth’s atmosphere at thousands of kilometres per hour on Sunday morning with bated breath. At 8:52 a.m. local time, it softly parachuted down onto the moist desert environment of the Utah Test and Training Range, which is located around 80 miles west of Salt Lake City.
The Origins, Spectral Interpretation, Resources Identification, and Security-Regolith Explorer (OSIRIS-REX) mission, which the capsule was part of, scored a huge victory with its successful landing. In 2016, a spacecraft was launched on a mission to the carbon-rich asteroid Bennu, which is roughly 190 feet broader than the Empire State Building is tall. This clean space soil is being studied for its potential to shed light on the origins of our solar system and life on Earth.
NASA administrator Bill Nelson remarked that the mission demonstrates NASA “does great things. Things that make us believe everything is possible, that bring us together, and that prove our limits are artificial.
It took the experts seven years of effort to finally gain NASA’s approval for the expedition. OSIRIS-REX was the first American spacecraft to bring back samples from an asteroid, and its efforts paid off when it brought back an unprecedented amount of material for researchers across the world to analyse. But for the OSIRIS-REX crew, many of whom “grew up on this mission,” as Dr. Lauretta put it, the project’s successful conclusion has much deeper significance.
The near-Earth asteroid Bennu is now a great distance from Earth, some millions of kilometres away. Like other asteroids, it is a geological relic of the protoplanetary disc that ringed our sun billions of years ago, a whirling mix of gas and dust that eventually solidified into planets. Some scientists believe that life on Earth was seeded by microworlds like Bennu.
However, Dr. Lauretta notes that it is challenging to verify this theory using meteorites, which are fragments of asteroids that reach Earth’s surface and are subsequently heated by the atmosphere and polluted by bacteria on the ground.
The return of an asteroid fragment to Earth is nothing new. Hayabusa, a mission headed by the Japanese space agency JAXA in 2010, was able to collect less than a milligramme of material from the near-Earth asteroid Itokawa, despite experiencing technical difficulties. Hayabusa2, a follow-up mission that arrived at Ryugu ten years later, brought back a few grammes of space rock. The existence of uracil, a building block of RNA, a chemical that aids in the formation of proteins, and other data imply that water was supplied to the early Earth by asteroids.
The arrival of OSIRIS-REX will bring with it a plethora of fresh supplies of space rock. About a half pound of pure asteroid soil is expected to be recovered. University of Tokyo planetary scientist and co-investigator on OSIRIS-REX Shogo Tachibana says has “no idea” whether Bennu will be anything like Ryugu, but that finding out is what he is most looking forward to.
This was always going to be a long mission. The OSIRIS-REX mission began with a proposal from a team of American scientists in 2004. Category 4, or “thanks, but no thanks,” is NASA’s lowest grade, and Dr. Lauretta was told to expect it when she submitted the proposal. The initial suggestion completely failed.
After three tries, it finally worked. The project was chosen by NASA in 2011. Harold Connolly, a cosmochemist at Rowan University who joined OSIRIS-REX 15 years ago, remarked, “So that began our real journey.” After the spacecraft was designed and built, the journey to Bennu was mapped out, and the research campaign was planned, the team spent another half a decade “making sure all our little ducks were in a row,” he added.
Experts on the mission thought the surface of Bennu would be like a sandy sea, with small particles spread evenly throughout the surface. As the asteroid came into focus, however, its stony surface and scattered rocks up to 10 storeys in height became clear. That made it more difficult to locate a spot where the spacecraft could collect a surface sample without harm.
As the engineers were trying to figure out what was wrong, Bennu threw them another curveball by spewing rubble into space. NASA’s OSIRIS-REX mission was “really exciting scientifically,” according to Lockheed Martin’s OSIRIS-REX programme manager Sandy Freund. However, “from an engineering standpoint,” this finding presented a new challenge.
The OSIRIS-REX team worked feverishly to ensure that the spacecraft would not be damaged by the asteroid’s gravelly plumes. Because of Bennu’s rough terrain, the operations team had to quickly write new navigation software.
Finding a spot where the spacecraft could collect fine grain regolith without risking damage to the ship was the next major challenge. Bennu’s rocky terrain makes it more challenging to do so. Images of the asteroid revealed sandy patches, but only within the craters’ bowl shapes. Dr. Lauretta reportedly replied, “We got to get inside one of those,” causing the surgery team much concern. The options are exhausted; “there’s nowhere else to go.”
There wasn’t much room for mistake. If the landing had gone awry, the spaceship may have met the same fate as Hayabusa, which crashed into its asteroid. OSIRIS-REX might also encounter “the banana peel scenario,” in which it slides down a slope and plunges into a crater, as described by Dr. Lauretta.
After two years of research, the mission team settled on a location near the asteroid’s north pole and gave it the name Nightingale. OSIRIS-REX pounded Bennu’s surface in October 2020 with a tool designed to “bounce off” Bennu.
