Science This Week | NASA’s OSIRIS-REx to bring back asteroid fragments

The 110-pound, 31-inch-wide sample return capsule, which had been launched from the OSIRIS-REx mothership four hours earlier and was carrying a half-pound of rocks and dirt that had been taken in 2020 from the asteroid known as Bennu, slammed into the top of the atmosphere 82 miles above Earth at a dizzying 27,700 mph at 10:42 a.m. EDT

NASA's OSIRIS-REx Is About to Bring Asteroid Pieces Back to Earth 

A celestial memento has been brought back by NASA's OSIRIS-REx spacecraft seven years after it departed for the near-Earth asteroid Bennu. A canister containing around 9 ounces of space rock will be released by the probe early on September 24 when it passes past Earth. At around 8:55 a.m. Mountain time, the container will launch into the stratosphere, open its parachute, and land on the Utah desert.

If its contents make it through the journey intact, the return will represent an exciting advancement in planetary research. Examining immaculate asteroid fragments has long caused researchers to salivate. Even though meteorites—often fragmented pieces of asteroids—fall from the sky frequently, the ground they strike immediately contaminates them. 

Scientists will be able to learn more about Bennu's composition and origins thanks to this unique opportunity to observe an unpolluted rock from space. After trips by the Japanese space agency to Ryugu and Itokawa, if the mission is a success, it will be just the third asteroid sample return in history.

It's also "a little bittersweet," according to the mission's lead investigator, planetary scientist Dante Lauretta, because the programme is finally coming to a close. In spite of this, he continues, "I'm excited to get it into the laboratory, so we can do all this amazing science." His team from the University of Arizona will analyse the make-up of the dust and rock pieces inside the container and search for any possible organic compounds. The scientists will also be able to compare samples of Bennu to Ryugu.

NASA spacecraft brings asteroid samples back to Earth

The capsule, which is spherical and about the size of an ice chest, must first arrive on Earth without incident. That will require decreasing speed from 28,000 mph to only 11. The spacecraft was built by Lockheed Martin for NASA, and they are also in charge of the capsule retrieval. Sandra Freund, a systems engineer at Lockheed and the OSIRIS-REx programme manager, refers to earlier NASA missions that recovered materials from a comet and the solar wind. "We have done sample returns before, so we have that experience," she adds. "We are certain that we can accomplish this, but returning something back to Earth is never without risk. You can experience atmospheric reentry, which is really ferocious. The parachutes you have need to open. So there are a number of things that need to go just right.”

A meteor or unprotected satellite of that size flying through the atmosphere would burn up at 5,000 degrees Fahrenheit without the capsule's built-in heat barrier. "You need to protect a payload whenever you wish to transport it through the environment. Todd White, a scientist at NASA Ames Research Centre in Mountain View, California, who developed on the spacecraft's thermal protection system, believes that it can be quite dangerous. The heat shield is ablative, which means that it slowly burns off. It is constructed of a lightweight chopped carbon fibre that has been mixed with resin. "It looks nice and brown on the back and white on the front—but when it lands, it'll look charred and crispy," adds White.

The capsule will first release a little drogue chute to stabilise itself. It will open its main parachute after seven minutes of descent and continue to fall for another six minutes. The first people to see its quick drop will be the recovery helicopters. When it lands in the isolated Utah Test and Training Range and Dugway Proving Grounds of the Department of Defence, relatively soft terrain ought to soften the effect. However, because it is an active range, a military officer will search the area to make sure there are no unexploded bombs before NASA staff arrive to recover the container.

The mission's first difficulty won't be a safe landing. In the beginning, the OSIRIS-REx team anticipated that the probe would collect fine-grained sand similar to what the Japanese space agency found on the asteroid Itokawa in 2005. But the surface of Bennu wasn't like that. It turned out to be much more rocky, more resembling a scattering of stones that had become loosely connected in the low gravity. Bits of regolith got stuck in what may have been an overly full collection head since it provided little resistance to OSIRIS-REx's robotic arm when it tried to collect the sample. Unintentionally, some of the material that OSIRIS-REx was able to gather was released back into space. Lauretta anticipates that the canister's exterior will be covered in asteroid dust given how that sample collecting went. 

Japan's Hayabusa2 mission collected 0.2 ounces of dust from Ryugu in 2020. Ryugu is a C-type, or carbonaceous, asteroid that has a soot-like appearance. Bennu is a B-type, which indicates it is abundant in minerals and carbon. The rock samples might indicate more significant variations between them, such as their origins. "I'm hopeful we can learn more about this object's past. We'll comprehend the diversity within the solar system by contrasting it with the history we're learning from the Ryugu samples, claims Deborah Domingue, a scientist at the Planetary Science Institute in Tucson, Arizona, who studied Ryugu material.

For instance, researchers could find out if Bennu has been struck by numerous other objects throughout the years or if an asteroid caused it to fall off of a larger parent body. These analogies are significant because asteroids are the basic components of planets; stony rocks similar to them adhered to one another 4.5 billion years ago to form the planets we see today. According to Domingue, no two planets in our solar system are comparable.

NASA has already sampled other celestial objects, even though this is only the third asteroid sample to be collected from space. In 2004, solar wind atoms were returned back by the Genesis expedition. The Stardust mission brought back a little chunk of a comet two years later. Both OSIRIS-REx and Stardust made desert landings in Utah, and Stardust used a comparable capsule. NASA is also preparing to launch its first Mars sample return mission later this decade, which will send some of the painstakingly collected rock samples from the Perseverance rover back to Utah.

The sample return by OSIRIS-REx is the beginning of what NASA has called "Asteroid Autumn." The Psyche mission of the space agency is set to blast off on October 5 in the direction of a sizable, metal-rich asteroid belt object after a protracted delay. (It might be postponed once more if the federal government shuts down on October 1 over conflicts over funding legislation.) On November 1, the Lucy spacecraft will take pictures as it passes by an asteroid in the inner belt known as 1999 VD57.

There is a market for mining asteroids because some of them may contain water ice, iron, nickel, or platinum-group metals. Earlier this year, the California-based business AstroForge tested its refining processes on asteroids-like material in Earth orbit. It wants to conduct a demonstration trip early in the following year to fly near asteroids and analyse their composition. The TransAstra Corporation, which is likewise situated in California, has received some NASA contracts and has been investing in mining technology and space tugs. The future viability of the new industry is not yet known. Planetary Resources and Deep Space Industries, earlier space mining companies, have already closed their doors.

OSIRIS-REx will carry on after its flyby of Earth to investigate the near-Earth asteroid Apophis, which it will get to in 2029. To reflect its extended mission, it will be renamed OSIRIS-APEX.

NASA and its allies will repackage the recovered capsule in the interim. They will then transfer it to NASA's Johnson Space Centre in Houston after purging it with nitrogen gas to ensure that it doesn't become contaminated by terrestrial microbes. It will be partially disassembled in a lab within a week or so, allowing the OSIRIS-REx crew to glimpse its interior for the first time. NASA will webcast a capsule unveiling on October 11. Lauretta and his other researchers will have to wait for the time being.