WEBVTT FILE

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[Music]

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This is Bennu: a
near-Earth asteroid, a remnant

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from the origins of the solar
system, and the target of NASA’s

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OSIRIS-REx mission.

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When OSIRIS-REx arrived in
December 2018, it brought Bennu

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into focus, confirming early
radar images that suggested the

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asteroid was shaped
like a spinning top.

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But the close-up images
also brought a big surprise.

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Before OSIRIS-REx arrived,
scientists had expected Bennu’s

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surface to consist largely of
fine-grained material, like a

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sandy beach.

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Sand heats up quickly during the
day, and cools off quickly at

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night.

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In contrast, solid objects like
rocks and boulders heat up and

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cool down more slowly.

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Infrared telescope observations
had shown that as Bennu rotates,

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its surface rapidly heats and
cools – much like a sandy beach.

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But OSIRIS-REx was greeted by
a rocky world littered with

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boulders – the size of cars,
the size of houses, the size of

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football fields.

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This unexpected roughness
confronted the mission with a

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major challenge.

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The main science goal of
OSIRIS-REx is to briefly touch

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down on Bennu, and grab a sample
of fine-grained material for

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return to Earth.

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To protect the spacecraft,
the original plan called for

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touchdown in a boulder-free zone
with a diameter of at least 164

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feet.

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But as it turns out,
boulder-free sites of that size

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don’t exist.

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Following arrival, mission
planners began looking at safe

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zones that are just a few
parking spaces wide, with enough

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loose material to
provide a sample.

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In mid-2019, they identified
four candidate sites, and named

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them after birds that can
be found in Egypt: Osprey,

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Kingfisher,
Nightingale, and Sandpiper.

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Mission planners evaluated each
site based on its safety to the

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spacecraft, the ease of getting
to the site, the amount of

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sampleable material that it
contains, and the science value

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of the material itself.

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After carefully evaluating these
criteria, they chose Nightingale

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as the primary sample collection
site and Osprey as the backup.

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Nightingale is located
near Bennu’s north pole.

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It sits inside a small crater
measuring 66 feet in diameter.

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Nightingale contains mostly
fine-grained material, and has

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multiple areas for
sample collection.

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It is also the darkest of the
candidate sites, and has high

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color variation,
suggesting a diverse mineralogy.

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Osprey is also located within a
66-foot-wide crater. just north

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of Bennu’s equatorial bulge, and
may contain rock types from both

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the northern and
southern hemispheres.

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Osprey has the strongest signal
for carbon-rich materials of all

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four sites, and contains a dark
patch at its center that is of

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high scientific
interest to the mission.

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Now that the primary and
backup sites have been chosen,

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OSIRIS-REx is performing
additional reconnaissance

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flights to prepare for the
sample collection event.

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Later in 2020, the spacecraft
will descend to Bennu’s surface,

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briefly touch down, and collect
up to four-and-a-half pounds of

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loose material.

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After collection, OSIRIS-REx
will carefully stow the sample

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and make the long
journey back to Earth.

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In late 2023 it will return
the sample, delivering pristine

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material from the origins of
the solar system that will be

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studied on Earth
for decades to come.

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[Music]