A NASA spacecraft that's spent the last few years collecting soil samples from a 4.5 billion-year-old asteroid is headed back to Earth in a journey that will take a little over two years.
The OSIRIS-REx fired its main engines full throttle for seven minutes on Monday afternoon, a move that pushed it away from the near-Earth asteroid Bennu at 600 miles per hour, NASA said in a press release.
That thrust away from Bennu will send the spacecraft on its journey toward Earth, where it will return with about 2 ounces of soil, rocks and dust from the asteroid's surface. NASA previously said OSIRIS-Rex's mission would help scientists investigate how planets formed and how life began, as well as improve their understanding of asteroids that could impact Earth.
The OSIRIS-REx launched in September 2016 from Cape Canaveral Air Force Station and reached Bennu in 2018.
It will now circle the sun twice inside of Venus' orbit before returning to Earth on Sept. 24, 2023, where the capsule containing the surface samples will separate from the rest of the spacecraft and enter Earth's atmosphere before eventually parachuting down to awaiting scientists at the Utah Test and Training Range in Utah's West Desert.
"OSIRIS-REx's many accomplishments demonstrated the daring and innovate way in which exploration unfolds in real time," Thomas Zurbuchen, associate administrator for science at NASA Headquarters, said in a statement. "The team rose to the challenge, and now we have a primordial piece of our solar system headed back to Earth where many generations of researchers can unlock its secrets."
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A dozen navigation engineers worked to create calculations and computer codes to ensure the OSIRIS-REx would be able to successfully push itself away from Bennu when the time came — and now that that's done, getting it back to Earth with its samples safely intact is the next "critical goal," according to the release.
To do that, engineers are using NASA's Deep Space Network of global spacecraft communications facilities to steer the OSIRIS-REx by sending it radio signals.
They'll need to perform course adjustments in the weeks before re-entry to ensure the location and angle are accurate; if the spacecraft comes in too low, it could bounce out of the atmosphere. If it comes in too high, the capsule could burn up due to friction and heat from the atmosphere, the release said. Should the OSIRIS-REx fail to release its capsule, a backup plan is in place to divert it away from Earth and give it another shot in 2025.
According to NASA, it's been an interesting journey for the spacecraft. When it first reached Bennu, the team realized that the asteroid was releasing small pieces of rock into space, and they had to ensure that none would damage the spacecraft. They were later surprised to learn that Bennu's surface is covered in boulders, and is not flat as expected.