A NASA spacecraft has successfully landed briefly on an asteroid before taking off again – hopefully grabbing some pieces of the asteroid in the process.
Today at 6.10 P.M. Eastern Time, the van-sized OSIRIS-REx sent a signal that it had reached the surface of the asteroid, touching its surface for just a few seconds. By firing a puff of gas into the surface, scientists are now hoping the arm has scooped material from the asteroid – called Bennu – ready to return to Earth.
“I can’t believe we actually pulled this off,” Dante Lauretta from the University of Arizona, the lead on the mission, said shortly after the landing. “This is history. It’s amazing.”
While the landing actually occurred 18 minutes earlier, the spacecraft and asteroid’s distance of 334 million kilometers from Earth meant the team had to wait for the signal to arrive to confirm the touchdown was successful.
Now the team will be anxiously waiting for the spacecraft to send back images and to see how much sample the spacecraft managed to grab from the surface of the asteroid. If it’s deemed to be enough, they can begin to plan for the journey home.
OSIRIS-REx was launched in 2016, on a mission to the asteroid Bennu – which has a similar orbit to Earth, albeit slightly larger. The goal is to grab samples from the asteroid and return them to Earth, the first asteroid sample return mission in NASA’s history.
It’s thought asteroids like Bennu could have delivered the building blocks of life to Earth and other worlds. Thus, studying samples from this asteroid back on Earth could have significant implications for our own origins, perhaps helping to explain how life on Earth began.
After the spacecraft reached the asteroid in 2018, the mission’s team began studying its surface, looking for a landing spot. They settled on a relatively flat area called Nightingale, just ten meters across, equivalent to a few parking spaces.
Following a couple of rehearsals, today was set as the date to attempt actually landing on the asteroid. Four and a half hours prior to the landing, the spacecraft was commanded to autonomously descend towards the surface.
After about four hours, the spacecraft fired its thrusters in a “checkpoint burn”, 125 meters above the surface, beginning its descent. About 11 minutes later it performed a “checkpoint burn” reducing its speed to a relative velocity of just ten centimeters per second.
Finally, the spacecraft’s extended TAGSAM (Touch-and-Go Sample Acquisition Mechanism) arm contacted the surface, with a spring mechanism bringing the spacecraft to a halt. Nitrogen canisters then fired gas into the surface, hopefully kicking material up into the head of the arm, where it should be captured in its rim.
The spring mechanism then pushed the spacecraft away from the surface before its thrusters fired – dodging a dangerous large nearby boulder called Mount Doom – to take the spacecraft up to a safe distance away from the asteroid.
Here, within a few days, the team will spin the spacecraft with its TAGSAM arm extended. By measuring the inertia of the spacecraft on this spin, they will be able to work out how much sample the spacecraft has collected from the surface.
The team are expecting anywhere from 60 grams up to two kilograms – roughly the weight of a brick. Any less, and they may return to a second planned landing site called Osprey later this year to attempt another sample capture.
If the amount of sample is deemed to be enough, however, the spacecraft will leave Bennu in March 2021. It will then make a two-year voyage home, ultimately dropping a capsule containing the samples into our atmosphere in September 2023, which will parachute to a landing in the Utah desert.
For NASA, this mission is a complete first; it has never attempted to return material from an asteroid to Earth, although it has returned material from a comet’s tail. It is also the largest sample return mission in history beyond missions to the Moon.
However, it is not the first such asteroid mission. Two Japanese spacecraft have achieved the feat before, Hayabusa1 in 2010, which returned just one millionth of a gram from the asteroid Itokawa, and Hayabusa2, expected to return up to a gram when it returns in December this year.
Now the OSIRIS-REx team face an anxious wait to see how much sample they have scooped up. If it’s enough, they’ll be able to breathe a sigh of relief and prepare for the journey home. If not, they’ll soon need to start planning for another nerve-wracking descent to the surface of Bennu.