Nasa's Osiris-Rex spacecraft has started its two-and-a-half-year return journey to Earth, carrying a 60g sample of ancient asteroid dust that may hold clues to the formation of the Solar System. The probe began its trek home on Monday at 16:16 EDT (21:16 GMT) from the near-Earth asteroid Bennu.
The sample, collected in a historic 'touch-and-go' manoeuvre in October 2020, is the largest since the Apollo Moon missions. Scientists believe the debris, which is as old as the Solar System itself, could reveal insights into the chemistry that formed the Sun and planets more than 4.5 billion years ago.
Osiris-Rex launched in 2016 and arrived at Bennu in 2018, mapping its surface and breaking records for the closest orbit of a planetary body. Bennu, discovered in 1999, is about half a kilometre wide at its equator and makes a close approach to Earth every six years.
The spacecraft will now circle the Sun twice to align with Earth, changing velocity by 595mph (958 km/h) to intersect our planet. It will travel a total of 1.4 billion miles (2.3 billion km) before releasing a capsule containing the sample into the Utah desert on 24 September 2023.
After landing, the capsule will be taken to Nasa's Johnson Space Center in Houston, Texas, for analysis. Nasa plans to preserve 75% of the sample for future generations to study with advanced technologies.
