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Af­ter a two-year chase, a NASA space­craft ar­rived Mon­day at the an­cient as­teroid Bennu, its first vis­i­tor in bil­lions of years.

The robotic ex­plorer Osiris-Rex pulled within 12 miles (19 kilo­me­ters) of the di­a­mond-shaped space rock. It will get even closer in the days ahead and go into or­bit around Bennu on Dec. 31. No space­craft has ever or­bited such a small cos­mic body.

It is the first U.S. at­tempt to gather as­teroid sam­ples for re­turn to Earth, some­thing only Japan has ac­com­plished so far.

Flight con­trollers ap­plauded and ex­changed high-fives once con­fir­ma­tion came through that Osiris-Rex made it to Bennu — ex­actly one week af­ter NASA landed a space­craft on Mars.

“Re­lieved, proud, and anx­ious to start ex­plor­ing!” tweeted lead sci­en­tist Dante Lau­retta of the Uni­ver­sity of Ari­zona. “To Bennu and back!”

With Bennu some 76 mil­lion miles (122 mil­lion kilo­me­ters) away, it took seven min­utes for word to get from the space­craft to flight con­trollers at Lock­heed Mar­tin in Lit­tle­ton, Colorado. The com­pany built the space­craft there.

Bennu is es­ti­mated to be just over 1,600 feet (500 me­ters) across. Re­searchers will pro­vide a more pre­cise de­scrip­tion at a sci­en­tific meet­ing next Mon­day in Wash­ing­ton.

About the size of an SUV, the space­craft will shadow the as­teroid for a year, be­fore scoop­ing up some gravel for re­turn to Earth in 2023.

Sci­en­tists are ea­ger to study ma­te­rial from a car­bon-rich as­teroid like dark Bennu, which could hold ev­i­dence dat­ing back to the be­gin­ning of our so­lar sys­tem 4.5 bil­lion years ago. As such, it’s an as­tro­nom­i­cal time cap­sule.

A Ja­panese space­craft, mean­while, has been hang­ing out at an­other near-Earth as­teroid since June, also for sam­ples. It is Japan’s se­cond as­teroid mis­sion. This lat­est rock is named Ryugu and about dou­ble the size of Bennu.

Ryugu’s specks should be here by De­cem­ber 2020, but will be far less than Osiris-Rex’s promised booty.

Osiris-Rex aims to col­lect at least 60 grams, or 2 ounces, of dust and gravel. The space­craft won’t land, but rather use a 10-foot (3-me­ter)

me­chan­i­cal arm in 2020 to mo­men­tar­ily touch down 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 big­gest cos­mic haul since the Apollo as­tro­nauts hand-de­liv­ered moon rocks to Earth in the late 1960s and early 1970s.

NASA has brought back comet dust and so­lar wind par­ti­cles be­fore, but never as­teroid sam­ples. Japan man­aged to re­turn some tiny par­ti­cles in 2010 from its first as­teroid mis­sion , also named Hayabusa.

Both Bennu and Ryugu are con­sid­ered po­ten­tially haz­ardous as­ter­oids. That means they could smack Earth years from now. At worst, Bennu would carve out a crater dur­ing a pro­jected close call 150 years from now.

Con­tact with Bennu will not sig­nif­i­cantly change its or­bit or make it more dan­ger­ous to us, Lau­retta stressed.

Sci­en­tists con­tend the more they learn about as­ter­oids, the bet­ter equipped Earth will be in head­ing off a truly cat­a­strophic strike.

The $800 mil­lion Osiris-Rex mis­sion be­gan with a 2016 launch from Cape Canaveral, Flor­ida. Its odome­ter read 1.2 bil­lion miles (2 bil­lion kilo­me­ters) as of Mon­day.

Both the space­craft and as­teroid’s names come from Egyp­tian mythol­ogy. Osiris is the god of the af­ter­life, while Bennu rep­re­sents the heron and cre­ation.

Osiris-Rex is ac­tu­ally a NASA acro­nym for ori­gins, spec­tral in­ter­pre­ta­tion, re­source iden­ti­fi­ca­tion, se­cu­rity-re­golith ex­plorer.

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