Extract from ABC News
A NASA spacecraft has touched the surface of asteroid Bennu, 200 million miles away from Earth, to collect a handful of rubble thought to contain the building blocks of our solar system.
Key points:
- The spacecraft took more than four hours to descend to the ancient asteroid
- Contact with the surface only lasted up to 10 seconds
- After nearly two years orbiting Bennu, it attempted to grab 60 grams of rubble
The Osiris-Rex spacecraft dropped out of orbit around asteroid Bennu right on time, beginning a four-and-a-half hour plunge to the rough, boulder-covered face of the ancient space rock.
It was the United States' first attempt to gather samples from an asteroid, something already accomplished twice by Japan.
The gravity of Bennu, which is just 510 metres in diameter, was too low for the spacecraft to land.
As a result, Osiris-Rex has to reach out with its 3.4-metre robot arm while dodging boulders the size of buildings.
It attempted to grab at least 60 grams of Bennu.
The rubble grab was the most harrowing part of the mission, which began with a launch from Cape Canaveral back in 2016.
"We'll only be kissing the surface with a short touch-and-go, measured in just seconds," mission deputy scientist Heather Enos said.
A van-sized spacecraft with an Egyptian-inspired name, Osiris-Rex aimed for a spot equivalent to a few car parking spaces in the middle of the asteroid's Nightingale Crater.
After nearly two years orbiting Bennu, the spacecraft found this location had the biggest patch of particles small enough to be swallowed up.
The plan called for Osiris-Rex to shoot out pressurised nitrogen gas to stir up the surface, then suck up any loose pebbles or dust.
Contact was expected to last only as long as 10 seconds, with the spacecraft quickly backing away.
NASA won't know until later this week how much was actually collected, or whether the spacecraft got anything at all.
Unlike the exceptionally fast Mars descents — described by NASA as seven minutes of terror — "this is much more of 4 1/2 hours of mild anxiousness", Ms Enos said on the eve of the big grab.
"We have practiced and rehearsed with the spacecraft … so we've seen almost all of this already."
Osiris-Rex got as close as 40 metres from the surface of Bennu during the final dry run in August.
By the time flight controllers near Denver hear back from Osiris-Rex, around 18 minutes will have passed since it made surface contact, as it takes this much time for radio signals to travel from Bennu to Earth.
Scientists want to get between 60 grams and 2 kilograms of Bennu's black, 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.
"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.
Osiris-Rex can make up to three touch-and-go maneuvers in case one comes up short.
Regardless of how many tries it takes, the samples won't return to Earth until 2023 to close out the $800-plus million quest.
The sample capsule will parachute into the Utah desert.
"That will be another big day for us. But this is absolutely the major event of the mission right now," NASA scientist Lucy Lim said.
AP/Reuters
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