After a long, successful and fascinating journey, NASA's OSIRIS-REx spacecraft is finally about to bring its precious cargo back to Earth.

The mission will drop off its collection box on 24 September before returning to space on another mission.

The cargo it will deliver consists of dust and rubble samples from Bennu, a carbon-rich asteroid thought to have formed very early in the history of the Solar System and drifted relatively unchanged over the 4.5 billion years since then.

OSIRIS-REx carries about 250 grams (8.8 ounces) of priceless Bennu soil in its collection box. The canister will be dropped into a 59-kilometre by 15-kilometre ellipse (37 miles by 9 miles) inside the US Department of Defence test and training range in the Utah desert.

NASA scientists estimate that the capsule will enter the Earth's atmosphere at 14.41 UTC (10.41 EDT) and land about 13 minutes later.

The entire process will be broadcast live starting at 10.00 a.m. EDT and a press conference will be organised at 11.00 a.m. EDT. This live broadcast will be available on NASA Live, NASA TV and the NASA app.

The cargo to be released is a major event. It represents the largest haul of asteroid debris ever brought to Earth, but this is only the third haul so far. Japan's collections from asteroids Itokawa and Ryugu returned in 2010 and 2020 respectively.

But Bennu is a particularly exciting asteroid. It is classified as type B, meaning it is thought to contain volatile elements in addition to its high carbon content. It is essentially a time capsule of the early Solar System that could help answer questions such as whether Earth's water and other components necessary for life were brought by asteroids and meteorites.

"There are two things that are common on Earth: water and biology," says astrochemist Jason Dworkin, OSIRIS-REx project scientist at NASA Goddard. "Both can severely alter meteorites when they land and blur the story told by the chemistry and mineralogy of the sample. An intact sample can provide insights into the development of the Solar System."

OSIRIS-REx's mission was carefully executed. Launched from Earth in September 2016, the spacecraft spent just over two years travelling to the asteroid, whose orbit approaches Earth every six years. In December 2018, OSIRIS-REx orbited Bennu and spent the next two years observing and approaching the asteroid to collect samples.

It set off on its return journey to Earth in May 2021, and NASA scientists have been preparing for the return ever since. Once the capsule is collected, it will be immediately taken to a portable clean room on site to ensure minimal contamination of the Earth.

In addition, scientists will take samples of the soil and air around the capsule's landing site. Once these samples are opened and analysed, they can be compared with the sample to detect local contaminants. We won't know the results of the first analysis until 11 October, but that's not too long to wait. After all, these are the big questions that scientists hope a cup of stardust will answer.

"This is all about understanding our origins," OSIRIS-REx principal investigator Dante Lauretta said in 2020, "it addresses some of the most fundamental questions we ask ourselves as human beings: Where did we come from? And are we alone in the universe?"

Source: https://www.sciencealert.com/