NASA’s rationale behind reaching an asteroid that may collide with Earth

The OSIRIS-REx mission will deliver NASA’s first asteroid sample collected in space to Earth on Sunday, September 24.

Travelling at about 44,500 km per hour as it enters the atmosphere, the mission’s spacecraft will release a capsule containing a sample of rock and dust from asteroid Bennu, and land in the Utah desert, where scientists are eagerly awaiting to retrieve it.

OSIRIS-REx is an acronym for Origins, Spectral Interpretation, Resource Identification, and Security-Regolith Explorer.

The sample return capsule is due to touch down at 8:55 a.m. MDT (10:55 a.m. EDT/9:55 a.m. CDT). Estimated to hold about half a pound of Bennu’s material, or 250 grams +/- 101 grams, this is the largest asteroid sample ever received on Earth.

NASA’s OSIRIS-REx mission is led by principal investigator Dante Lauretta, a regents professor of planetary science and cosmochemistry at the University of Arizona’s Lunar and Planetary Laboratory.

Believed to boast organic compounds and water-bearing minerals, Bennu is a carbon-rich, near-Earth asteroid.

The collected asteroid sample is expected to open decades of research opportunities, bringing scientists closer to answering how planets form and the way life began, including how Earth’s oceans got their water, as well as deepen human understanding of asteroids that could collide with Earth.

Bennu’s size and orbit make it a potentially hazardous asteroid.

Every six years the asteroid passes about 300,000 km from the planet’s surface, which is closer than the orbit of the moon, and has a 1 in 2,700 chance of hitting Earth by September 2182, according to data from the OSIRIS-REx science team.

The asteroid was first discovered in 1999, and is named after the ancient Egyptian deity Bennu, thought to symbolise the sun, creation, and rebirth.

Measuring a diameter of about 492 metres — slightly wider than the height of the Empire State Building or Malaysia’s Petronas Twin Towers — Bennu has over 4.5 billion years of history.

It is considered an ancient remnant of our solar system’s early days, which is why scientists think its organic molecules may have played a role in the inception of life on Earth.

NASA’s OSIRIS-REx is not the first mission to deliver an asteroid sample to Earth.

In June 2010, the Japan Aerospace Exploration Agency’s (JAXA) Hayabusa mission brought back specks from asteroid Itokawa, while the JAXA Hayabusa2 mission delivered about five grams of asteroid sample from Ryugu in November 2021.

The OSIRIS-REx spacecraft, approximately the size of a 15-passenger van, was launched on September 8, 2016. It began its two-and-a-half-year journey back to Earth in May 2021 after successfully collecting pieces of Bennu in October 2020.

NASA will be live streaming the landing at the Utah Test and Training Range from 10 am EDT (8 am MDT/9 am CDT) on September 24 on its YouTube channel and NASA TV.