As OSIRIS-REx Returns to Earth from Asteroid Bennu

Subject: Science and technology

Section: Space technology

Source: The wire

Context:

NASA’s Origins, Spectral Interpretation, Resource Identification, Security–Regolith Explorer (OSIRIS-REx) mission returns to Earth carrying an estimated 250 grams (8.8 ounces) of material gathered from the surface of an asteroid.
The samples contained in the capsule may help distinguish true asteroid-origin materials and terrestrial contaminations or alterations for multiple meteorite types.

OSIRIS-REx mission:

OSIRIS-REx launched from Cape Canaveral, Florida in 2016 and spent two years traveling to Bennu, a carbon-rich asteroid that orbits between Earth and Mars.
The spacecraft arrived at the asteroid in December 2018 and orbited for two years, measuring the asteroid’s mass, density, albedo, surface composition and particle environment.
The landing site on Bennu was named: Nightingale.
Findings:
- During its reconnaissance of Bennu, the mission team discovered that the asteroid is of the rare active variety, meaning that it intermittently ejects material from its surface. The surface is far more rugged than expected, hosting several hundred boulders larger than ten meters in diameter.
- Bennu’s bulk density is lower than expected; as much as 60% of the asteroid might be empty space.
- The surface was covered with hydrated minerals that suggest past aqueous activity, and Bennu’s rotation is speeding up, likely caused by an interaction with solar radiation known as the YORP effect (Yarkovsky-O’Keefe-Radzievskii-Paddack).

Why return samples?

Material has been collected and returned to Earth from comets, asteroids, the solar wind and the Moon.
Samples returned directly from a source can answer many scientific questions that can’t be answered by remote observations, landers and rovers, or even meteorites fallen to Earth.
Many details hidden within a rock can be lost during a meteorite’s atmospheric entry and impact but are preserved with a returned sample.
Earlier samples returned from asteroids Itokawa and Ryugu had been analyzed, which were the targets of past missions of the Japan Aerospace Exploration Agency (JAXA).
The Hayabusa spacecraft collected evidence of space weathering on Itokawa, and Hayabusa2 found that Ryugu is made of carbon-rich rocks, known as carbonaceous chondrites, that closely trace the Sun’s composition. The Ryugu samples revealed that the few meteorites of the same classification that have fallen to Earth were chemically altered by the journey.

Planning for the future:

This will be NASA’s first sample return mission since Stardust in 2006 and Genesis in 2004.
Japan’s Hayabusa and Hayabusa2 missions returned samples in 2010 and 2020, respectively, and China’s Chang’e 5 mission brought lunar samples back in 2020.
The OSIRIS-REx science team will retain 25% of the material. The Canadian Space Agency will receive 4% for its contribution to the spacecraft’s instrumentation, and JAXA will receive 0.5% in exchange for samples from both Hayabusa missions.