After a two-year chase, a NASA spacecraft has arrived at the ancient asteroid.
The robotic explorer Osiris-Rex on Monday pulled within 19km of the diamond-shaped space rock , Bennu on December 31. No spacecraft has ever orbited such a small cosmic body.
It is the first attempt to collect asteroid samples for return to Earth, something only Japan has come so far.
Hello, asteroid Bennu! Our @OSIRISREx spacecraft flew over 2 billion miles to meet you. Here, the spacecraft's camera captures a full rotation of the asteroid. OSIRIS-REx wants to study Bennu for almost a year & prepare to collect and return a sample to Earth. https://t.co/WG3vVeRoV1
– NASA (@NASA) December 3, 2018
"Relieved, proud, and anxious to start exploring!" Tweeted lead scientist Dante Lauretta of the University of Arizona. "To Bennu and back!"
With Bennu some 122 million miles away, it took seven minutes to get to the spacecraft at Lockheed Martin in Littleton, Colorado. The company built the spacecraft there.
Bennu is just over 500 meters across. Researchers will provide a more detailed description of the next meeting in Washington, DC.
About the size of an SUV, the spacecraft will shadow the asteroid for a year, before scooping up some grave for return to Earth in 2023.  To Bennu and back! https://t.co/i4i3564jZK
– Dante Lauretta (@DSLauretta) December 3, 2018
Scientists are eager to study material from a carbon-rich asteroid like dark Bennu, which could have been dating back to the beginning of our solar system 4.5bn years ago , It's an astronomical time capsule.
A Japanese spacecraft, meanwhile, has been hanging out at another near-Earth asteroid since June, so for samples. It is Japan's second asteroid mission. Ryugu's specks should be by December 2020, but will be less than Osiris-Rex's promised booty.
Osiris-Rex aims to collect at least 60 grams of dust and gravel. The spacecraft will not land, but rather use a three-meter mechanical arm in 2020 to momentarily touch and vacuum up particles. The sample container would break loose and head toward Earth in 2021.
The collection – parachuting down to Utah – would represent the greatest cosmic haul since the Apollo astronaut's hand-delivered moon rocks to Earth in the late 1960s and early 1970s.  NASA has brought back dust and solar wind particles before, but never asteroid samples. Japan manages to return some tiny particles in 2010 from its first asteroid mission, so named Hayabusa.
Both Bennu and Ryugu are considered to be potentially hazardous asteroids. That means they could be smack Earth years from now. 150 years from now.
Scientists contend the more they Earth is ready for a catastrophic strike.
The $ 800m Osiris-Rex mission started a 2016 launch from Cape Canaveral, Florida. Its odometer read two billion kilometers as of Monday.
Both the spacecraft and asteroid's names come from Egyptian mythology. Osiris-Rex is actually a NASA acronym for origins, spectral interpretation, resource identification, security-regolith explorer.