A NASA mission begun in 2016 is finally about to reach its goal: touching down on an asteroid.
On Tuesday, the spacecraft OSIRIS-REx will attempt to collect a sample from an asteroid called Bennu. This is NASA's first-ever asteroid sample return mission.
"It's a pretty bold mission," says Dean Regas, Cincinnati Observatory astronomer and host of the Looking Up podcast. "This is sending a robotic spacecraft to an asteroid where it will touch down and collect some samples and then fly all the way back and return these samples to Earth."
NASA explains asteroids are remnants of "the building blocks that formed" our solar system. The goal is learning more about their organic make-up, and possibly, the origin of life. Regas points out it's uncertain what the samples could contain and teach us.
"Is it going to bring back some elements that could be pointing toward things that were on early Earth, or are we going to see something completely different? It's kind of an unknown in a lot of ways," says Regas.
It's important to learn about asteroids, also, because they can be dangerous. Bennu has a one in 2,700 chance of hitting Earth in the late 2100s, according to NASA. Data obtained from the samples could help scientists learn more about protecting our planet.
"We're going to be watching this asteroid very carefully and seeing how its orbit changes over time," Regas says. "This could lead us to some ideas of how we can actually move asteroids out of the way. Things that we see that are coming toward Earth that could potentially hit us, we have to do some practicing to see if we can actually move an asteroid out of the way. That's the best chance we have of avoiding these impacts."
While this is NASA's first asteroid sample collection and return mission, it's not the first ever. The Japanese spacecraft Hayabusa was the first to return samples from an asteroid in 2010, and Hayabusa-2 is scheduled to return to Earth Dec. 6, 2020.
It will be a while before OSIRIS-REx returns with its samples, assuming the procedure goes as planned. The spacecraft, which launched Sept. 8, 2016, is expected to return to Earth on Sept. 24, 2023.
Relatively speaking, the asteroid isn't that far away from Earth. Its orbital period is 1.2 years, coming close to Earth every six years. So, why does the mission take so long? Regas says the timing has to be just right.
"The way that our two orbits are, we have to go in this trajectory to approach it very slowly," Regas explains. "It's got such a small gravity well that if you miss it you fly right by, so you have to go at just the right speed to catch up to it and enter into its orbit. It's really complicated to fly to such as small object."
Bennu is approximately 510 m in diameter from its poles. By comparison, NASA points out the Empire State Building is 443 m.