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In late 2018, as NASA’s
OSIRIS-REx spacecraft neared its

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target, Bennu, the asteroid grew
in detail from a few tiny pixels

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to an incredibly hi-resolution
image. OSIRIS-REx confirmed the

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asteroid’s basic shape, which
was originally observed in 1999

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by ground-based radar at Arecibo
Observatory. What scientists

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didn’t expect was just how rough
and boulder-filled the asteroid

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would turn out to be. While it
can be difficult to fully grasp

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Bennu’s unfamiliar surface, it’s
helpful to understand the scale

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of what you’re seeing here. In
this image, the brightest

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boulder is the length of a horse
and the large boulder in this

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image is the width of a soccer
field. Another challenge for the

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mission is the asteroid’s small
size and weak gravity. This

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means that OSIRIS-REx needs to
fly daringly close to the

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surface in order to enter into
orbit. With its orbital A phase,

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OSIRIS-REx successfully entered
the closest-ever orbit for a

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spacecraft, setting a Guinness
World Record in the process.

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Then, 6 months later, it beat
its own record during its

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orbital B phase and approached
to within a few hundred meters

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of the rocky surface. Because
OSIRIS-REx flew so closely over

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the surface during orbital B,
the team was able to map the

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topography and shape of Bennu
better than we have our own

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Moon. In addition to mapping
Bennu, OSIRIS-REx plans to

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collect and return a sample of
the asteroid back to Earth. To

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do that, the spacecraft will
carefully tag the surface of

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Bennu. The OSIRIS-REx team has
selected four possible sample

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sites for the mission: Osprey,
Kingfisher, Nightingale, and

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Sandpiper. The spacecraft has
been closely imaging these sites

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from different angles to select
the best touch-down spot for

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OSIRIS-REx. What was originally
envisioned as a smooth and easy

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touchdown on Bennu’s surface,
has become a complex endeavor to

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tag a small, crowded space on
the asteroid – an area no larger

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than a few parking spots, by mid
2020. The OSIRIS-REx team has

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already pushed the boundaries of
scientific exploration, going

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from ground-based radar images
all the way to being a few

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hundred meters from the asteroid
surface, and is now mere months

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away from a sample collection
attempt.