About 150 million years ago, Earth's
most recent supercontinent was in the process of breaking up.
Sauropods dominated the lush, slowly separating landmass
that would become today's familiar continents.
Meanwhile, in the asteroid belt,
a breakup of a different sort was taking place.
The large asteroid 163 Erigone was pummeled in a collision,
shedding debris to form a new family of asteroids.
Fast forward to 3.2 million years ago, long after the fall of the dinosaurs,
when an early hominin walked upright through an Ethiopian river valley.
Now, a robotic explorer named for our most famous
human ancestor is heading to a member of the Erigone asteroid family
en route to the fossils of planetary formation.
[Music]
Launch audio and commentary: “Liftoff! Atlas V takes flight.”
NASA's Lucy mission launched in October 2021
and flew past Earth in 2022 and 2024 for a pair of gravity assists.
In early 2025, Lucy entered the main asteroid belt,
on course for humanity's first encounter with
52246 Donaldjohanson.
The asteroid was named in honor of the paleoanthropologist
who discovered the Lucy fossil in 1974, rewriting the textbooks on human origins.
While asteroid Donaldjohanson has never been seen up close,
its brighrtness varies greatly as it rotates,
suggesting an elongated shape.
It is a member of the Erigone family of asteroids,
made from fragments of the collision
that took place about 150 million years ago.
Earth-based observations suggest that Donaldjohanson is
carobn-rich, has an average diameter of about four kilometers,
and spins on its axis extremely slowly,
giving it a 251-hour day.
On Sunday, April 20th, Lucy will approach Donaldjohanson from the direction
of the Sun, traveling 13.4km per second relative to the asteroid.
As its target grows near, the spacecraft will slowly rotate,
keeping the asteroid in view.
Over the course of a few hours, Donaldjohanson will transform
from a point of light into a detailed world.
Lucy's Long-Range Reconnaissance Imager will capture high-resolution pictures
throughout the flyby, providing our best look yet at the asteroid.
Just before closest approach,
when Lucy is about 900km from its target, it will abruptly turn its Instrument
Pointing Platform away from the Sun to protect its sensitive electronics.
Shortly after the flyby, Lucy will perform a “pitchback” maneuver,
changing the direction of its rotation to turn its high-gain-antenna toward Earth.
Two hours later, data from Lucy will deliver the first close-up views
of Donaldjohanson, a surviving remnant of the solar system's chaotic past.
Following the flyby,
Lucy will continue to pass through the main asteroid belt.
In August 2027, it will reach Eurybates, an asteroid more than ten times
larger than Donaldjohanson and a member of the Jupiter Trojans.
These primordial and primitive objects are trapped
in Jupiter’s orbit, and are considered the “fossils” of
planetary formation.
Between 2027 and 2033, Lucy will make five separate
encounters with Trojan asteroids and their moons.
It will become the first spacecraft to explore this
ancient population...
asteroids more than one thousand times older
than our most famous human ancestor...
formed at the dawn of the solar system,
long before dinosaurs ruled the Earth.
[Music]