NASA's first ever asteroid sample has landed on Earth

Seven years after setting out from Earth, NASA’s OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification and Security – Regolith Explorer) spacecraft has travelled nearly 4 billion kilometres across the solar system and back, to visit an asteroid named Bennu and collect a sample — a sample that has now been brought back to Earth.

At just 500 metres across, Bennu is about the same size as the length of five football fields, making it the smallest object ever to be orbited by a spacecraft. The asteroid is a collection of rocks and boulders that have accumulated under gravity over billions of years, with scientists hopeful that they’ll find water-bearing minerals that contain organic compounds — the building blocks of life on Earth. Knowing more about asteroids like Bennu is expected to help unlock the secrets of the formation of the early solar system, give further insights into the story of life on Earth, and provide greater knowledge to protect ourselves from potential threats from space.

OSIRIS-REx took a little over two years to reach Bennu and then spent two and a half years performing a detailed study of the asteroid with every instrument it had available. The mission team selected a collection site in what was thought to be a young crater, meaning they could collect rocks and dust ‘recently’ exposed and thus provide a pristine sample and insight into Bennu’s history. On 20 October 2020 a robotic sample arm briefly touched the surface of Bennu, collecting around 60 grams of regolith (dirt and rocks). OSIRIS-REx finally started heading home on 10 May 2021.

On 24 September 2023, OSIRIS-REx released the capsule containing the sample around 102,000 km from the Earth’s surface, with the capsule ultimately landing in a targeted area of the US Department of Defense’s Utah Test and Training Range near Salt Lake City. The sample has now been moved to its new home at NASA’s Johnson Space Center in Houston, where it will be cared for, stored and distributed to scientists worldwide.

Researchers will spend the next few weeks in a cleanroom at Johnson built exclusively for the Bennu sample, which includes custom glove boxes built to fit the sample canister containing the TAGSAM (Touch-and-Go Sample Acquisition Mechanism) head that was at the end of the robotic sample arm. The scientists and technicians will proceed through the many steps of removing the sample from the TAGSAM head, cataloguing and storing every piece of hardware and asteroid dust found outside of it.

The researchers plan to analyse asteroid dust from their initial disassembly for an early glimpse into the chemical, mineralogical and physical characteristics and rock types that may be found in the bulk sample, with NASA planning to share these initial findings, plus first images of the sample, in a live broadcast on 11 October. Scientists from Australia’s Curtin University, as members of the OSIRIS-REx science team, will later use their own sophisticated instruments to decipher the sample and gain invaluable insights into the origins of our solar system and life itself.

“Bennu is a lumpy C-group asteroid, a carbonaceous and volatile-rich group that has been relatively untouched since it was formed,” said Curtin Associate Professor Nick Timms. “This means we will effectively have a window to look back to the beginning of the solar system itself.

“These samples are some of the most pristine rocks available. Unlike natural meteor falls that can quickly become contaminated by our atmosphere, water and biota, these rocks are unblemished. So, with Bennu we will be analysing unspoilt samples of the oldest objects in the solar system.

“We’ll be able to tell a huge amount about what happened when the solar system was nothing more than dust and gas, and the processes that brought planets together and created the ingredients for life on Earth.”

The Director of Curtin’s Space Science Technology Centre, Professor Phil Bland, said the Curtin team has strengths in determining the age of small samples, learning the impact history and discovering chemical composition using a cutting-edge ‘atom probe’. Professor Fred Jourdan, the Director of the Western Australian Argon Isotope Facility, said the first wave of samples will consist of 5 mg of material that will be shipped directly to his laboratory at the end of October, with the first wave of results expected during the first half of 2024.

“Bennu is a rubble pile asteroid, which means that it is entirely made up of fragments ranging from boulders to dust that were ejected during the destruction of a much larger parent asteroid,” Jourdan said. “I’m very excited to apply my own argon-argon dating technique to see when this happened.”

“This mission’s significance lies in its enduring nature,” Bland concluded. “OSIRIS-REx didn’t just go to an asteroid or planet, do its work there and come back — it was actually a sample return mission, where material can be analysed for decades, offering continuous revelations about our cosmic origins.

“Just as we are still learning things from the samples the Apollo astronauts brought back, more than 50 years ago, so too we will be able to uncover the secrets of Bennu for decades to come.”

Image caption: The sample return capsule from NASA’s OSIRIS-REx mission is seen shortly after touching down in the desert on 24 September 2023. Image credit: NASA/Keegan Barber.