Lucy Mission Overview: Journey to Explore the Trojan Asteroids

The Lucy Mission is going to
fly past seven asteroids in twelve years with one
spacecraft. We are going to an amazing variety of objects with
this mission, and it’s really almost pure luck that allowed us
to get as many rich targets as we are. Literally, the planets
were aligning to allow us to do this mission. The Lucy Mission
is named after the Lucy fossil, the Australopithecus fossil,
that was discovered in the 1970s in Ethiopia. And just like the
Lucy fossil transformed our understanding of hominid
evolution, the Lucy Mission will transform our understanding of
Solar System evolution. Trojan Asteroids are an interesting
population of small bodies that are left over from the formation
of the planets. And they lead or follow Jupiter in its orbit by
roughly sixty degrees. If you just look at the gravitational
attraction of the Sun and Jupiter and put something
exactly sixty degrees in front of Jupiter, it’s stable forever.
So, as a result these objects are really the leftovers of
planet formation. The stuff that went into growing Jupiter and
Saturn are now trapped in these locations. The very first
asteroid we get to is a main belt asteroid named
DonaldJohanson. We named that asteroid in honor of the
researcher who found the Lucy fossil. We’re going to use that
asteroid to do a rehearsal on our spacecraft to make sure that
everything is working properly so that when we get to the
Trojan asteroids, we’re ready to go. We’re visiting both of the
Trojan swarms. In the first orbit, we’re going into the
leading swarm and we’re going to encounter four Trojan targets:
Eurybates, Polymele, Leucus, and Orus. And from this, we’re going
to sample the diversity in sizes, colors, and compositions.
The first two flybys happen just about thirty days apart, so it’s
going to be a pretty busy kickoff to the season of
exploring the asteroids in the L4 swarm. And then, we’ll fly
past Earth again and out to the L5 swarm. The final object we’re
visiting, which I must admit is my favorite, is a binary object.
So, that’s two Trojans that orbit a common center of mass,
it’s called Patroclus and Menoetius. These objects are
nearly identical in size that orbit one another. From the Lucy
Mission we’re going to study the diversity of our targets because
that tells us something about their origin and where they came
from. The interesting thing about small bodies in general is
that they are the leftovers of planet formation. If you look at
the eight planets that we know about, for example, they are
highly processed because of internal processing. These
asteroids are objects that really haven’t changed much from
when the planets assembled themselves. As a result, by
studying them we can figure out the physical conditions of the
early Solar System as well as how the planets grew and how
they moved around early on. All of that will help us form a
detailed picture of what these objects really look like because
right now our best images are just a point of light. Even
using the Hubble Space Telescope or adaptive optics on large,
ground-based telescopes, we can’t see surface details. And
it’s going to take the Lucy Mission to go to these targets
and see what they’re really made of and what they look like.

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