CAPE CANAVERAL, Florida (AP) – After nearly two years of circling an ancient asteroid hundreds of millions of miles away, a NASA spacecraft this week will attempt to descend to the treacherous, boulder-filled surface and snatch a handful of rubble.
The drama unfolds on Tuesday as the United States takes its first crack at collecting asteroid samples to return to Earth, a feat so far only achieved by Japan.
The Osiris-Rex mission is filled with names inspired by Egyptian mythology and seeks to bring back at least 60 grams of asteroid Bennu, the largest feature from countries other than the moon.
The van-sized spacecraft aims at the relatively flat center of a crater the size of a tennis court called the Nightingale ̵
“So for some perspective, think about the challenge of navigating Osiris-Rex into one of these places 200 million miles away the next time you park your car in front of your house or in front of a cafe and enter.” said NASA’s Deputy Project Manager Mike Moreau.
Once it falls out of its half-kilometer high (0.75-kilometer-high) orbit around Bennu, the spacecraft will deliberately take four hours to get all the way down to just above the surface.
Then the action swings up as Osiris-Rex’s 11-foot (3.4-meter) arm extends and touches Bennu. Contact should last five to ten seconds, just long enough to release nitrogen gas under pressure and soak up the cooled dirt and gravel. Programmed in advance, the spacecraft will operate autonomously during the unprecedented touch-and-go maneuver. With an 18-minute delay in radio communications each way, ground controls for spacecraft builder Lockheed Martin near Denver cannot intervene.
If the first attempt does not work, Osiris-Rex can try again. All collected samples first reach the earth by 2023.
While NASA has brought back comet dust and solar wind particles, it has never tried to test one of the nearly 1 million known asteroids lurking in our solar system to date. Japan, meanwhile, expects to receive samples from the asteroid Ryugu in December – in milligrams at most – 10 years after bringing spots back from the asteroid Itokawa.
Bennu is a paradise for the asteroid voter.
The large, black, round, carbon-rich space rock – taller than New York’s Empire State Building – was around when our solar system formed 4.5 billion years ago. Scientists consider it a time capsule full of pristine building blocks that can help explain how life was formed on Earth and possibly elsewhere.
“This is about understanding our origins,” said the mission’s lead researcher, Dante Lauretta of the University of Arizona.
There are also selfish reasons to get to know Bennu better.
The asteroid orbiting the sun, which orbits the Earth every six years, could target us late in the next century. NASA sets the odds for a 1-in-2,700 impact. The more scientists know about potentially threatening asteroids like Bennu, the safer Earth will be.
When Osiris-Rex jumped out in 2016 on the more than $ 800 million mission, scientists imagined stretches of sand at Bennu. So the spacecraft was designed to take up small pebbles less than an inch (2 inches) across.
Scientists were amazed to find massive rocks and lumps of gravel everywhere when the spacecraft arrived in 2018. And occasionally pebbles were seen shooting off the asteroid, falling back and sometimes ricocheting out again in a cosmic game of table tennis.
With so much uneven terrain, engineers struggled to aim for a tighter spot than originally expected. Nightingale Crater, the primary target, appears to have the largest abundance of fine grains, but there are still plenty of rocks, including one called Mount Doom.
Then COVID-19 struck.
The team fell behind and encountered the second and final touch-and-go dress rehearsal for the spacecraft for August. It pushed the sample to October.
“It’s hard to return a sample,” said NASA’s head of science mission, Thomas Zurbuchen. “COVID made it even harder.”
Osiris-Rex has three bottles of nitrogen gas, which means it can stir three times – no more.
The spacecraft will automatically return if it encounters unexpected dangers such as large rocks that can cause it to topple over. And there is a chance that it will surely stir but not collect enough rubble.
In either case, the spacecraft would return to orbit around Bennu and try again in January elsewhere.
With the first attempt finally here, Lauretta is worried, nervous, excited “and convinced that we have done everything we can to ensure safe sampling.”
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