CAPE CANAVERAL, Florida (AP) – After nearly two years in orbit around 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 rip a handful of rubble.
The drama unfolds Tuesday as the United States makes its first attempt to collect asteroid samples for return to Earth, a feat so far only accomplished by Japan.
Packed with names inspired by Egyptian mythology, the Osiris-Rex mission is seeking to bring back at least 2 ounces (60 grams) of asteroid Bennu, the largest otherworldly loot from beyond the moon.
The van-sized spacecraft aims at the relatively flat center of a tennis court-sized crater called the Nightingale, a spot comparable to some parking lots here on Earth. Boulders as large as buildings loom over the targeted landing zone.
“So, for some perspective, next time you park your car in front of your house or in front of a coffee shop and walk in, think about the challenge of driving Osiris-Rex to one of these spots from 200 million miles away.”
Once it descends from its half-mile (0.75-kilometer) orbit around Bennu, the spacecraft will deliberately take four hours to get to just above the surface.
Then the action escalates as Osiris-Rex’s 11-foot (3.4-meter) arm reaches out and touches Bennu. Contact should last 5 to 10 seconds, which is enough time to release pressurized nitrogen and vacuum up the agitated dirt and gravel. Scheduled in advance, the spacecraft will operate autonomously during the unprecedented touch-and-go maneuver. With an 18-minute delay in radio communications in each direction, ground controllers at spacecraft manufacturer Lockheed Martin near Denver are unable to intervene.
If the first attempt fails, Osiris-Rex can try again. All the samples collected will not reach Earth until 2023.
Although NASA has reported comet dust and solar wind particles, it has never attempted to sample any of the nearly 1 million known asteroids lurking in our solar system until now. Japan, meanwhile, expects to obtain samples from asteroid Ryugu in December – at most in milligrams – 10 years after returning the grains from the asteroid Itokawa.
Bennu is an asteroid collector’s paradise.
The large black, rounded, carbon-rich space rock – taller than New York’s Empire State Building – was around when our solar system was forming 4.5 billion years ago. Scientists see it as a time capsule filled with pristine building blocks that could help explain how life was formed on Earth and possibly elsewhere.
“It’s about understanding our origins,” said the mission’s principal scientist, Dante Lauretta of the University of Arizona.
There are also selfish reasons for getting to know Bennu better.
The asteroid in solar orbit, which oscillates close to the Earth every six years, could point at us at the end of the next century. NASA estimates the odds of an impact at 1 in 2,700. The more scientists know about potentially threatening asteroids like Bennu, the safer Earth will be.
When Osiris-Rex took off in 2016 for the more than $ 800 million mission, scientists imagined sandy stretches in Bennu. So the spacecraft was designed to ingest small pebbles less than one inch (2 centimeters) in diameter.
When the spacecraft arrived in 2018, scientists were amazed to find massive boulders and thick gravel everywhere. And occasionally pebbles have been seen shooting from the asteroid, falling, and sometimes bouncing back in a cosmic game of ping-pong.
With so much rough terrain, the engineers were quick to aim for a tighter spot than originally intended. The nightingale crater, the main focus, appears to have the greatest abundance of fine grains, but boulders still abound, including one nicknamed Mount Doom.
Then COVID-19 struck.
The team fell behind and blocked the second and final touch-and-go dress rehearsal for the spacecraft in August. This prompted the sample collection to October.
“Returning a sample is difficult,” said Thomas Zurbuchen, head of NASA’s science mission. “COVID has made everything even more difficult.”
Osiris-Rex has three nitrogen gas cylinders, which means it can land three times, no more.
The spacecraft will automatically retract if it encounters unexpected hazards such as large rocks that could cause it to overturn. And there is a chance it will land safely, but fail to collect enough rubble.
Either way, the spacecraft would return to orbit around Bennu and try again in January at another location.
With the first attempt finally here, Lauretta is worried, nervous, excited “and confident that she has done everything possible to ensure safe sampling”.
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