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OSIRIS-REx was designed to

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retrieve a sample from asteroid Bennu
and return it to Earth.

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So of the more than 1 million
known asteroids

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in our solar system, why Bennu?

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First, as a near-Earth asteroid,
Bennu is easy to reach.

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It takes about 14 months to orbit
the sun and comes

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close to earth once
every six years to get there.

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OSIRIS-REx was launched
in 2016 on an Atlas

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five rocket with a single booster
and a center upper stage.

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It also got a big assist from Earth's
gravity in 2017,

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allowing it to match Bennu's orbital tilt.

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The second reason that Bennu was
chosen was its size and spin rate.

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Bennu measures about half a kilometer
in diameter and rotates

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on its axis once every 4.3 hours,

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which is actually pretty slow
compared to many smaller asteroids.

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This allowed OSIRIS-REx to map
Bennu surface up close

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and to match its velocity briefly
touch down and collect a sample.

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Before OSIRIS-REx arrived, scientists
thought that Bennu's slow rotation

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meant a low risk of flinging away
most of its sample material.

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But shortly after arrival,

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Bennu was caught on camera,
ejecting hundreds of pebbles.

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It turns out that Bennu
regularly sheds small particles, but

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it still had plenty of loose material left
on its surface for sample collection.

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The third reason for choosing
Bennu was its composition.

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We don't know what ingredients
were present during the formation of life

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on Earth,
but primitive asteroids like Bennu serve

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as time capsules, preserving material
from the dawn of the solar system.

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Spectrometers on

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OSIRIS-REx confirmed that Bennu is rich
in carbon based molecules,

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including organics
that are the stuff of life.

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When the Bennu sample is analyzed,
it will help scientists to better

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understand the formation
of the solar system and our own origins.

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So why this particular asteroid proximity
to Earth?

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The right size and spin and a carbon
rich composition?

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That is why we chose Bennu.