Nasa's Osiris-Rex asteroid chaser passes Earth on way to space rock
Nasa's asteroid-chasing spacecraft is swinging by Earth on its way to a space rock.
Launched a year ago, Osiris-Rex is on track to pass within about 11,000 miles of the home planet above Antarctica, using Earth's gravity as a slingshot to put it on a path towards the asteroid Bennu.
Osiris-Rex should reach the small, roundish asteroid next year and, in 2020, collect some of its gravel for return to Earth. If all goes well, scientists should get the samples in 2023.
Friday's fly-by is a quick hello. The spacecraft will zoom by at about 19,000mph, and Nasa has taken precautions to ensure Osiris-Rex - about the size of a large car - does not slam into any satellites.
"Everything looks great! Thanks for the well wishes," the University of Arizona's Dante Lauretta, chief scientist for Osiris-Rex, said on Twitter.
Ground telescopes have been trying to observe the spacecraft while it is in the neighbourhood, and Nasa has posted a picture gallery online.
The organisation expects to be out of contact with Osiris-Rex for about an hour during the fly-by as it will be too close for the Deep Space Network communication relay.
Bennu is just 1,640ft across and circles the sun in an orbit slightly wider than ours.
Osiris-Rex will go into orbit around the asteroid and seek the best spot for grabbing a few handfuls of the bite-sized bits of rock.
It will hover like a hummingbird as a mechanical arm briefly rests on the surface and sucks in samples stirred up by nitrogen gas thrusters.
Scientists say the ancient asteroid could hold clues to the origin of life. It is believed to have formed 4.5 billion years ago, a remnant of the solar system's building blocks.
This is the first US attempt to bring back samples from an asteroid. Japan has already visited an asteroid and returned some specks.