NASA’s OSIRIS-REx touches asteroid for rare rubble grab

The sampling arm of the OSIRIS-REx spacecraft as it practices its approach to Bennu

Oct. 20, 2020 4:52 PM PT

CAPE CANAVERAL, Fla. — A NASA spacecraft descended to an asteroid Tuesday and, dodging boulders the size of buildings, momentarily touched the surface to collect a handful of cosmic rubble for return to Earth.

It was a first for the United States — only Japan has scored asteroid samples.

“I can’t believe we actually pulled this off,” said Dante Lauretta of the University of Arizona, lead scientist for the $800-million mission. “The spacecraft did everything it was supposed to do.”

The OSIRIS-REx spacecraft sent back confirmation of its contact with asteroid Bennu more than 200 million miles away, drawing cheers from the mission team. But it could be a week before scientists know how much, if anything, was grabbed and whether another try will be needed.

If successful, OSIRIS-REx will deliver the samples in 2023.

Following commands sent well in advance by ground controllers near Denver, the spacecraft took 4½ hours to make its way down from its tight orbit around Bennu.

Bennu’s gravity was too low for OSIRIS-REx to land — the asteroid is just 1,670 feet across. As a result, the spacecraft had to reach out with its 11-foot robot arm as it attempted to grab at least 2 ounces, or 60 grams, of Bennu.

The University of Arizona’s Heather Enos, deputy scientist for the mission, described it as “kissing the surface with a short touch-and-go measured in just seconds.”

At Mission Control for spacecraft builder Lockheed Martin, controllers on the TAG Team — for touch-and-go — wore royal blue polo shirts and black masks with the mission patch. The COVID-19 pandemic had resulted in a two-month delay.

Tuesday’s operation was considered the most harrowing part of the mission, which began with a launch from Cape Canaveral back in 2016.

A van-sized spacecraft with an Egyptian-inspired name, OSIRIS-REx aimed for a spot equivalent to a few parking spaces on Earth in the middle of the asteroid’s Nightingale crater. After nearly two years orbiting Bennu, the spacecraft found this location to have the biggest patch of particles small enough to be swallowed up.

Once it determined that the coast was clear, OSIRIS-REx closed in the final few yards for the sampling. The spacecraft was programmed to shoot out pressurized nitrogen gas to stir up the surface, then suck up any loose pebbles or dust. Contact was expected to last a mere 5 to 10 seconds, with the spacecraft quickly backing away.

By the time flight controllers heard back from OSIRIS-REx, the action already happened 18½ minutes earlier — the time it takes radio signals to travel from Bennu to Earth.

Scientists want between 2 ounces and 4 pounds of Bennu’s black, crumbly, carbon-rich material, which is thought to contain the building blocks of our solar system.

NASA’s science mission chief, Thomas Zurbuchen, likened Bennu to the Rosetta Stone. It’s “something that’s out there and tells the history of our entire Earth, of the solar system, during the last billions of years,” he said.

Another benefit: Bennu has a slight chance of smacking Earth late in the next century, although not as a show-stopping life-ender. The more scientists know about the paths and properties of potentially hazardous space rocks like this one, the safer we’ll all be.

OSIRIS-REx can make two more touch-and-go maneuvers in case this one comes up short. Regardless of how many tries it takes, the samples won’t make it to Earth until 2023, when they’ll parachute into the Utah desert inside a capsule.

“That will be another big day for us,” NASA scientist Lucy Lim said. “But this is absolutely the major event of the mission right now.”

Japan expects samples from its second asteroid mission — in the milligrams at most — to land in the Australian desert in December.

NASA, meanwhile, plans to launch three more asteroid missions in the next two years. All of those will be one-way trips.