A NASA spacecraft carrying space rock fired its main engines full throttle and began the long journey back to Earth, bidding farewell to its 4.5-billion-year-old asteroid companion.
The OSIRIS-REx spacecraft, NASA's first asteroid sample return mission, will take two-and-a-half-years to complete the 2.3 billion-kilometre trip home, the space agency said.
Although the asteroid is a mere 287 million kilometres away, the car-size spacecraft will circle the sun twice before delivering its small sample capsule to Utah's desert floor on September 24, 2023.
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The robotic prospector reached asteroid Bennu in 2018 and spent two years flying near and around it, before landing and collecting samples of rock and dust from the asteroid¡¯s surface in October.
OSIRIS-REx will bring back the largest sample collected by a NASA mission since the Apollo astronauts returned with Moon rocks. And while the space agency has returned comet dust and solar wind samples before, this is the first time it's gone after pieces of an asteroid.
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Scientists plan to analyze the sample to learn about the origins of our solar system, the sources of water and organic molecules on Earth, the resources in near-Earth space, as well as improve our understanding of asteroids that could impact Earth.
The spacecraft has collected more than 2.1 ounces (60 grams) of asteroid material. Once recovered, the capsule will be transported to the curation facility at NASA¡¯s Johnson Space Center in Houston, where the sample will be removed for distribution to laboratories worldwide.
NASA plans to set aside 75 per cent of the samples for future generations to study with technologies not yet created.
OSIRIS-REx made history many times during its two-and-a-half years of operations on the asteroid, including breaking its own record for the closest orbit of a planetary body by a spacecraft. Also, Bennu is the smallest celestial object ever orbited by a human-built spacecraft.
The OSIRIS-REx mission also confirmed and refuted several scientific findings. The mission verified a technique that used observations from Earth to predict that the minerals on the asteroid would be carbon-rich and show signs of ancient water.
Scientists had also predicted that the asteroid would have a smooth surface by measuring how much heat radiated off its surface. But they were surprised to find that Bennu¡¯s entire surface is rough and dense with boulders.
¡°This mission emphasizes why we have to do science and exploration in multiple ways--both from Earth and from up-close in space-because assumptions and models are just that,¡± said Heather Enos, OSIRIS-REx deputy principal investigator.