On Oct. 20 just after 6 p.m EDT, NASA will attempt a daring touch-and-go when its little-probe-that-could, OSIRIS-REx, tries to snatch a piece of an asteroid.
The van-sized probe will have three chances to extend its 11-foot arm and touch down on the asteroid Bennu for five seconds, blowing pure nitrogen gas onto the surface and hopefully kicking up a meaningful amount of dust and pebbles to capture and bring back home.
The sampler head that will touch the asteroid is a bit larger than a dinner plate, and the goal is for it to collect anywhere from 60 grams to 2 kilograms (about 2 ounces to 4.5 pounds) of material. If the mission is successful, scientists will use the samples to learn more about both Bennu’s origins—what minerals it’s made of and where they came from—and our own. Bennu is considered a “primitive asteroid,” which formed something like 4.5 billion years ago and hasn’t changed much since then. That means we might find organic molecules on its surface that can teach us about the beginnings of life on Earth.
Researchers will also measure the Yarkovsky effect on Bennu, or the way heat from the sun can change its path over time. That’s especially important because there’s a chance that Bennu, which is about the size of the Empire State Building, might crash into Earth sometime late next century. Understanding more about its potential trajectory could help future missions seeking to stop that kind of impact.
OSIRIS-REx (whose name is an acronym that refers to its research goals) launched from Cape Canaveral, Florida, in late 2016; orbited the sun for a year; and then met up with Bennu in 2018. Since then, it’s been observing its traveling companion closely, mapping Bennu’s surface and practicing flybys at different—and sometimes seriously low—altitudes. In December 2019, the mission team chose primary and backup sites for touchdown, two relatively smooth patches inside craters among a sea of boulders.
Tuesday’s touch-and-go sample collection represents the culmination of all of that effort and exploration. After its attempt(s) at extraterrestrial darts, the probe will go back to orbit before returning home in 2023 with whatever bits of Bennu it managed to grab.