Context: The OSIRIS-REX mission has ended with the return of regolith (space sample) from the primordial asteroid Bennu.
- Origins, Spectral Interpretation, Resources Identification and Security-Regolith Explorer (OSIRIS REx) is an asteroid study and sample return mission by NASA.
- The spacecraft set out in 2016 to study asteroid Bennu (a carbon-rich near-Earth asteroid) and return to Earth with a sample for detailed analysis in 2023.
- Bennu is a small asteroid, a little less than 500 metres in depth and is more than 4.5 billion years old.
- It is classified as a “near-Earth object” because it passes relatively close to our planet every six years.
- Over time, the asteroid has drifted closer to Earth, closely approaching it every six years, owing to which it has a small chance of impacting the Earth in future (2182 CE).
Why was Bennu chosen?
- Bennu fits in three criteria: accessibility, size and composition.
- For a mission like OSIRIS-REx, the most accessible asteroids are somewhere between 0.08 – 1.6 AU. Scientists needed an asteroid that could be easily travelled to, retrieve a sample from and return to Earth all within a few years. Further, Bennu had an orbit similar to Earth.
- One theory is that small worlds like Bennu seeded Earth with the prebiotic ingredients for life
- Researchers believe that this pristine space dirt will reveal clues about the birth of our solar system (4.5 billion years ago) and the genesis of life on Earth.
- One AU (Astronomical Unit) is approximately equal to 93 million miles – the distance between the Sun and the Earth. The closest asteroids which travel within 1.3 AU of the sun are called near-Earth objects.