After about two years spiraling an old asteroid hundreds of millions of miles away, a NASA spacecraft this week will try to go to the boulder-packed surface and collect a handful of rubble.
It was revealed on Tuesday as the U.S. carries its initial break at collecting asteroid samples for return to Earth, an accomplishment achieved so far by Japan.
The van-sized spacecraft is striving for the fairly flat middle of a tennis court-sized crater named Nightingale— a spot similar to a few parking spots here on Earth. Boulders as large as buildings loom over the targeted touchdown zone.
“So for some perspective, the next time you park your car in front of your house or in front of a coffee shop and walk inside, think about the challenge of navigating Osiris-Rex into one of these spots from 200 million miles away,” said NASA’s deputy project manager Mike Moreau.
The moment it lowers out of its half-mile-high (0.75 kilometer-high) orbit around Bennu, the spacecraft will take an intentional four hours to make it all the way down, to above the surface.
Then the trial cranks up when Osiris-Rex’s 11-foot (3.4-meter) arm reaches out and touch Bennu. Touch should last five to 10 seconds, to shoot out pressurized nitrogen gas and kowtow the churned dirt and gravel. Programmed in advance, the spacecraft will function autonomously during the unusual touch-and-go maneuver. With an 18-minute delay in radio transmission each way, ground regulators for spacecraft builder Lockheed Martin near Denver can’t intervene.
If the first trial fails, Osiris-Rex can attempt again. Any accumulated samples won’t get to Earth until 2023.
Although NASA has brought back comet dust and solar wind particles, it has never endeavoured to experiment one of the nearly 1 million known asteroids found in our solar system until now. Japan, meanwhile, awaits to get samples from asteroid Ryugu in December, 10 years after bringing back specks from asteroid Itokawa.
The huge, black, roundish, carbon-rich space rock was present when our solar system was shaping 4.5 billion years ago. Scientists evaluate it a time capsule full of pristine building blocks that could help understand how life developed on Earth and possibly elsewhere.
“This is all about understanding our origins,” said the mission’s principal scientist, Dante Lauretta of the University of Arizona.
The solar-orbiting asteroid, which swings by Earth every six years, could take advance towards us later in the next century. NASA sets the odds of a collision at 1-in-2,700. The further scientists understand about potentially endangering asteroids like Bennu, the safer Earth will be.
When Osiris-Rex launched in 2016 on the more than $800 million mission, scientists anticipated sandy stretches at Bennu. So the spacecraft was manufactured to gobble small pebbles less than an inch (2 centimeters) across.
Scientists were amazed to discover huge rocks and big gravel all over the place when the spacecraft reached in 2018. And pebbles were periodically detected hurling off the asteroid, tumbling back and periodically ricocheting off again in a cosmic contest of ping-pong.
With the bumpy topography, engineers vied to aim for a rigid spot than initially predicted. Nightingale Crater, the primary target, seems to have the largest amount of fine grains, but boulders were much, comprising one dubbed Mount Doom.
However, due to covid-19, the team fell behind and hit the second and final touch-and-go dress rehearsal for the spacecraft to August. That propelled the sample grab to October.
“Returning a sample is hard,” said NASA’s science mission chief, Thomas Zurbuchen. “The COVID made it even harder.”
The spacecraft automatically will return if it confronts unforeseen risks like big rocks that could result in it tipping over. And there is a likelihood it will touch down safely, but fail to accumulate sufficient rubble.
With the initial attempt eventually here, Lauretta is worried, nervous, excited “and confident we have done everything possible to ensure a safe sampling.”