OSIRIS-REx, the spacecraft carrying NASA’s first-ever asteroid sample, has started its two-year journey back to Earth, the space agency confirmed on Monday.
On Friday, ground control sent the commands directing the 2,110 kg (4,650 lb) vehicle to fire its main thrusters to get out of asteroid Bennu’s orbit and return to our planet. The team erupted in cheers on Monday after it received confirmation that OSIRIS-REx had successfully fired its engines at 2016 UTC, and was on its way.
"Mission navigation has received confirmation of burn cutoff. OSIRIS-REx is headed home with a souvenir of rocks and dusts from a 4.5-billion-year-old asteroid," the NASA team said.
Nearly five years after its launch in September 2016, the spacecraft is now coming back home with 60 grams of pristine dirt scraped from the surface of Bennu, a near-Earth asteroid. Space agencies around the world have increasingly taken an interest in asteroids since the late 1990s. The first spacecraft to ever orbit and land on a space rock was NASA’s Near Earth Asteroid Rendezvous – Shoemaker in 2000.
As technology improved, these missions became bolder. Japan’s Aerospace Exploration Agency successfully pulled off the world’s first and second asteroid sample return missions in 2005, and again in 2018 with its Hayabusa spacecraft.
Now, it’s NASA’s turn. OSIRIS-REx is expected to touchdown at the Utah Test and Training Range, a US military training ground, on September 24, 2023. The landing process will be tricky: the spacecraft has to intercept Earth as it orbits around the Sun. It will zoom 2.3 billion kilometres (1.3 billion miles) around the Sun twice to perform a gravity assist maneuver that will slingshot it toward our planet.
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Nearby asteroids are generally the leftover chunks of dirt and rock that didn’t quite make it into a planet during the formation of our Solar System some 4.5 billion years ago. Scientists believe they can use the collected asteroid material to find out more about how the Earth was formed and how life emerged, as rocks like Bennu can contain water, organic compounds, and metals. As they smashed into our young planet, they could have delivered the vital chemicals to support life.
NASA also wants to study asteroids to see if they could act as potential pit stops for future missions to stop and refuel. Astronauts might be able to extract materials to power their spacecraft as they travel out into space.
First, scientists will have to look at what goodies Bennu is made out of. They will analyze the chemical composition of the rock, measuring the abundances of its minerals and clays to estimate its water content. The sample will be sent to NASA’s Johnson Space Center in Houston, where they will be packed and shipped off to laboratories around the world. Most of the stuff, however, will be stored and kept for future generations of scientists to study.
OSIRIS-REx obtained a sample of the asteroid in October last year. It extended a 3.35-meter robotic arm to graze Bennu’s surface, and ejected puffs of nitrogen gas to kick up a cloud of dust which it then scooped up with a sampler head at the end of its arm.
The spacecraft also uncovered surprising features of the Empire State Building-sized asteroid. It is volatile and randomly flings fragments of debris as it spins, something scientists have called particle ejection events. Scientists later discovered how the process explained why the rock was shaped like a diamond.
NASA has also broken the record for the closest orbit of a planetary body by a spacecraft with OSIRIS-REx, and Bennu is the smallest space object to ever be orbited by a spacecraft, too. ®