After a four-year journey, the US National Aeronautics and Space Administration’s (Nasa’s) robotic spacecraft Osiris-Rex briefly touched down on asteroid Bennu’s boulder-strewn surface on Tuesday to collect rock and dust samples in a precision operation 330 million kilometres from Earth.
The so-called “Touch-And-Go” or TAG manoeuvre was managed by Lockheed Martin Space in Denver, Colorado, where at 6:12pm (2212 GMT) an announcer said: “Touchdown declared. Sampling is in progress,” and scientists erupted in celebration.
The historic mission was 12 years in the making and rested on a critical 16 second period where the spacecraft performed a delicate autonomous manoeuvre to grab its precious payload – at least 60g, or a candy-bar sized amount of regolith that scientists hope will help unravel the origins of our solar system.
If Osiris-Rex successfully comes home in September 2023, it will have collected the largest sample returned from space since the Apollo era.
NASA scientist Michelle Thaller said: “We think we actually might be coming back with a baby picture of what the solar system was like, of what our chemistry was like, billions of years ago.
“We’re looking for our own origins out there, and that’s why we’ve gone so far to bring a bit of Bennu back.”
The spacecraft, about the size of a large van, slowed down to a crawl of just 10cm per second on the final phase of its descent into the Nightingale crater on the north pole of the asteroid, which is 490m in diameter.
For size comparison, that is just a bit bigger than the Empire State building in New York City.
Osiris-Rex eased its robotic arm down to a target zone just 8m in diameter, then fired pressurised nitrogen to agitate the surface material and catch its sample.
Then the spacecraft fired its thrusters to back away from Bennu’s surface to complete what scientists playfully described as a “boop”.
Mission control and the public learned of all this about 18.5 minutes later than it actually happened because of the time it takes for the signals to return from the space rock, which for the most part orbits between Venus and Mars.
The first images will only be available on Wednesday once the probe is further away and has a higher data transmission rate.
We will have to wait until Saturday to find out if Osiris-Rex has succeeded in collecting the desired amount of dust.
Scientists want at least 60g but the spacecraft is capable of picking up as much as 2kg.
If it turns out the spacecraft didn’t collect enough, it will have another go on January 12, next year, at a backup site which is another relatively boulder-free area near the rock’s equator.