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The origin of life is
one of the deepest mysteries in science,

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but the clues to solving it
have been buried by plate tectonics,

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the water cycle, and even life itself.

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For answers, scientists are looking
beyond Earth to primitive asteroids

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like Bennu, the target of NASA's
daring OSIRIS-REx sample return mission.

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Now, material from Bennu
is revealing a lost world

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from the dawn of the solar system,

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with the right conditions

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to foster the building blocks of life.

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When scientists
examined the Bennu samples,

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they discovered evidence
of a wet and salty past.

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Among the dark rocks were bright
veins of salts

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that form on Earth
when brines evaporate from alkaline lakes.

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Searles Lake, California is home
to a mineral called trona,

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which is mined as a source of baking soda.

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Scientists found microcrystals of trona

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and other evaporate minerals
within the Bennu samples,

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indicating that they once held pockets
of sodium-rich water.

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Such brines are ideal for cooking up
organic molecules,

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carbon-based compounds
that are the stuff of life.

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Bennu is a carbon-rich
asteroid, and its samples are chock

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full of organics,
including amino acids and nucleobases.

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Amino acids can be bonded together
in long chains to build proteins,

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which give cells their structure
and function.

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Life is constructed from a set of 20
amino acids,

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14 of which were identified
within the Bennu samples.

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Nucleobases are the
genetic components of DNA and RNA.

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All five nucleobases were discovered
in the Bennu samples,

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a first for extraterrestrial material
collected by a spacecraft.

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In addition
to organic molecules, scientists

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found that the Bennu samples
are surprisingly rich in ammonia.

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On Earth, ammonia is a common
agricultural fertilizer.

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It readily evaporates at room temperature,
but is more stable in cold

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environments, like those found in the
outer solar system.

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Bennu is too close to the sun
to retain pure ammonia,

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so its samples must have formed during
a more distant, frigid past.

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Salts...organics...ammonia.

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Thanks to OSIRIS-REx,
we can now piece together these clues

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to tell a likely origin
story for asteroid Bennu.

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[Music beat]

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4.5 billion years ago,

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in the nascent solar system's
outer reaches,

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a world of rock, metal and ice took shape.

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Radioactive decay heated its interior,

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melting some of the ice. Pockets of
mineral-rich water

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reacted with formaldehyde and ammonia
to produce organics.

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As the water dried up, dissolved minerals

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crystallized, leaving
bright veins within the rocks.

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The world migrated closer to the sun,

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until it was shattered in a collision
and destroyed.

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Bennu accreted from the rubble
and drifted further inward, eventually

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settling into a near-Earth orbit
where it could be reached by OSIRIS-REx.

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Our planet was bombarded by asteroids
like Bennu early in its history,

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suggesting that many of the same organic
molecules were present on Earth

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before the dawn of life.

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[Music beat]

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These findings help to close a gap
in our understanding

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of the early solar system,
but key questions remain open.

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Many amino acids can be created
in two mirror image

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versions, like a
pair of left and right hands.

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Life on Earth almost exclusively produces
the left-handed variety,

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while the Bennu samples contain
an equal mixture of both.

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This means that on early Earth,
amino acids

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may have started out
in an equal mixture as well.

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The reason that life turned left
instead of right remains a mystery.

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Additional insights
may come in 2030, when NASA's

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Europa Clipper mission arrives
at Jupiter.

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It will hunt for evidence of a briny ocean
within the moon Europa,

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an environment favorable
to producing organics.

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Until then, scientists will dig deeper
into the Bennu samples,

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unearthing more molecular clues
about the origins of life.

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[Music]