NASA's OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) spacecraft has finally reached Asteroid Bennu, after a two-year-long journey through deep space.
The probe travelled about 2 billion kilometres and arrived at the 500m-wide rock on the 3rd December.
On Monday, the mission team commanded the probe to fire its thrusters for 20 seconds to match the asteroid's speed and direction, bringing the spacecraft to about 7km from Bennu at closest approach.
Asteroid Bennu was first spotted in 1999. It is a carbon-rich, near-Earth asteroid, believed to have been created by the leftovers from the formation of the solar system. It is also thought to have remained largely unchanged for the past 4.5 billion years.
There is a small chance of Bennu slamming into Earth, but not until the 22nd century. The impact, if it actually happens, will not cause the planet-wide destruction of The Great Dying, but would definitely be devastating at the point of impact.
In January, the probe will get closer to the asteroid - between 1.4 and 1.9 kilometres - before starting to orbit it. That will make Bennu the smallest object ever to be orbited by a spacecraft in space.
OSIRIS-REx will spend the next year surveying the asteroid to collect more information about its surface and composition. In mid-2020, the mission team will command the probe to slowly descend and bounce off the surface of the asteroid, to collect a sample of at least 60g of the top soil. NASA plans to bring the sample back to Earth in 2023, packed in a capsule.
OSIRIS-REx is carrying five scientific instruments with it that will enable scientists to select a safe and suitable location for soil sample collection.
The spacecraft will pass Earth in September 2023 and will drop off the capsule (with sample), which will land in the Utah desert using a parachute.
"As explorers, we at NASA have never shied away from the most extreme challenges in the solar system in our quest for knowledge," said Lori Glaze, acting director for NASA's Planetary Science Division.
"Now we're at it again, working with our partners in the US and Canada to accomplish the Herculean task of bringing back to Earth a piece of the early solar system."
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