Excitement is brewing in the world of space exploration as NASA’s OSIRIS-REx spacecraft prepares to make history by delivering a sample of asteroid Bennu to Earth. This monumental event marks the first time a U.S. mission has successfully collected and returned a piece of an asteroid.

The OSIRIS-REx mission, which commenced on September 8, 2016, achieved the remarkable feat of collecting approximately 8.8 ounces (250 grams) of rocks and dust from the surface of asteroid Bennu on October 20, 2020. This precious material from Bennu is nothing less than a time capsule, offering insights into the early days of our solar system and holding answers to fundamental questions about the origins of life and the nature of asteroids.

So, when and where can we expect this extraordinary cargo to land on Earth? The spacecraft will release the sample capsule when it reaches within 63,000 miles (102,000 kilometres) of Earth’s surface, approximately one-third of the distance from Earth to the Moon. This release is scheduled for 4:42 a.m. MDT / 6:42 a.m. EDT on September 24, 2023.

Traveling at a breakneck speed of 27,650 miles (44,500 kilometers) per hour, the sample capsule will enter Earth’s atmosphere four hours later, just off the coast of Northern California, at an altitude of approximately 83 miles (133 kilometers) above the surface. The entry is expected at 8:42 a.m. MDT / 10:42 a.m. EDT, and the capsule will touch down just 13 minutes later, at 8:55 a.m. MDT / 10:55 a.m. EDT. The landing site is a 36-mile by 8.5-mile (58-kilo-meter by 14-kilometer) area within the Department of Defences Utah Test and Training Range near Salt Lake City.

The mission team will act swiftly to retrieve the capsule and safeguard the sample from potential contamination by Earth’s environment. Helicopters will transport the capsule to a temporary clean room at the training range, and from there, it will journey to NASA’s Johnson Space Center in Houston the following day. Scientists at Johnson will be responsible for caring for, documenting, and distributing the sample to the OSIRIS-REx science team and researchers worldwide, ensuring that the wealth of knowledge it contains benefits generations to come.

But what makes Bennu and its sample so significant? Scientists speculate that Bennu originated from a larger asteroid in the asteroid belt over 1 to 2 billion years ago following a catastrophic collision. It’s characterised as a “rubble-pile” asteroid, composed of loosely packed rocks held together by gravity. Bennu is rich in organic molecules and has been altered by liquid water in its distant past, making it a compelling subject of study in the quest to understand the origins of key ingredients for life on Earth.

The decision to study Bennu was driven by several compelling reasons. It offers a glimpse into the tumultuous formation of our solar system around 4.5 billion years ago, a period obscured by weather and geological changes on Earth. Additionally, Bennu’s rich organic compounds could shed light on the delivery of these crucial elements for life to our planet through asteroid impacts. Unlike most asteroids, Bennu conveniently crosses Earth’s orbit, making it an ideal target for the OSIRIS-REx mission.

As for the potential impact of Bennu on Earth, the spacecraft’s data indicates that there’s no risk through the mid-2100s, and any subsequent chance is exceedingly slight, less than one-tenth of a percent through at least the year 2300. Predicting such events remains a crucial scientific goal of the mission.

In safeguarding the Bennu sample from Earthly contamination, NASA has taken meticulous precautions. During the capsule’s descent through Earth’s atmosphere, air entering through vents will pass through a filter that removes contaminants, ensuring the purity of the sample.

Rest assured, the Bennu sample poses no threat to Earth. The harsh radiation of space makes it impossible for living organisms to survive, and studies of space materials, including meteorites, cosmic dust, and previously returned samples, confirm the absence of hazardous chemicals or harmful radioactive materials.

As the OSIRIS-REx spacecraft embarks on its next mission to explore asteroid Apophis, set to reach its destination in 2029, the world awaits with anticipation for the extraordinary return of the Bennu sample. It will serve as a testament to human ingenuity, expanding our knowledge of the cosmos and potentially rewriting the history of our solar system. With distribution planned to a select group of scientists and preservation for future generations, the Bennu sample promises to be an invaluable treasure trove of scientific discovery.