Rubble from 81 million kilometres away: Capsule carrying asteroid secrets lands on Earth

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NASA’s first asteroid samples fetched from deep space parachuted into the Utah desert on Sunday to cap a seven-year journey.

In a flyby of Earth, the OSIRIS-REx spacecraft released the sample capsule from 100,000 kilometres out. The small capsule landed four hours later on a remote expanse of military land, as the mothership set off after another asteroid.

The asteroid Bennu as seen from the OSIRIS-REx spacecraft. Credit: NASA/Goddard/University of Arizona/CSA/York/MDA via AP

Scientists estimate the capsule holds at least a cup of rubble from a carbon-rich asteroid known as Bennu, but they won’t know for sure until the container is opened. Some material spilled and floated away when the spacecraft scooped up too much and rocks also jammed the container’s lid during collection three years ago.

Japan, the only other country to bring asteroid samples back to Earth, gathered only a teaspoon of material across two separate missions.

The pebbles and dust delivered on Sunday represent the biggest haul from beyond the moon. Preserved building blocks from the dawn of our solar system 4.5 billion years ago, the samples will help scientists better understand how Earth and life formed.

Helicopter recovery teams leave the Michael Army Air Field in Utah to collect the capsule.Credit: AP

OSIRIS-REx, the mothership, rocketed away on the billion-dollar mission in 2016. It reached Bennu two years later and, using a long stick vacuum, grabbed rubble from the small roundish space rock in 2020. By the time it returned, the spacecraft had logged 6.2 billion kilometres.

NASA’s recovery effort in Utah included helicopters as well as a temporary clean room set up at the Defence Department’s Utah Test and Training Range. The samples will be flown on Monday morning to a new lab at NASA’s Johnson Space Centre in Houston. The building already houses hundreds of kilograms of moon rocks gathered by the Apollo astronauts more than half a century ago.

The mission’s lead scientist, Dante Lauretta of the University of Arizona, will accompany the samples to Texas. The opening of the container in Houston in the next day or two will be “the real moment of truth,” given the uncertainty over the amount inside, he said ahead of the landing.

Engineers estimate the canister holds 250 grams of material from Bennu, plus or minus 100 grams. Even at the low end, it will easily surpass the minimum requirement of the mission, Lauretta said.

It will take a few weeks to get a precise measurement, said NASA’s lead curator Nicole Lunning.

NASA plans a public show-and-tell in October.

Currently orbiting the sun 81 million kilometres from Earth, Bennu is about half a kilometre in diameter or roughly the size of the Empire State Building. The asteroid is shaped like a spinning top. It is believed to be the broken fragment of a much larger asteroid.

During a two-year survey, OSIRIS-REx found Bennu to be a chunky rubble pile full of boulders and craters. The surface was so loose that the spacecraft’s vacuum arm sank around half a metre into the asteroid to suck up the material.

These close-up observations may come in handy late in the next century. Bennu is expected to come dangerously close to Earth in 2182 – possibly close enough to hit. The data gleaned by OSIRIS-REx will help with any asteroid-deflection effort, according to Lauretta.

OSIRIS-RExis already chasing after the asteroid Apophis and will reach it in 2029.

This was NASA’s third sample return from a deep-space robotic mission. The Genesis spacecraft dropped off bits of solar wind in 2004, but the samples were compromised when the parachute failed and the capsule slammed into the ground. The Stardust spacecraft successfully delivered comet dust in 2006.

NASA’s plans to return samples from Mars are on hold after an independent review board criticised the cost and complexity. The Martian rover Perseverance has spent the past two years collecting core samples for eventual transport to Earth.


Liam Mannix’s Examine newsletter explains and analyses science with a rigorous focus on the evidence. Sign up to get it each week.

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