NASA’s Lucy Mission: Unlocking the Fossils of the Solar System

Ryan Bale
Apr 20
3 min read

“Lucy” isn’t just the name of a fossilized human ancestor — it’s also NASA’s first spacecraft on a mission to explore the Trojan asteroids, ancient remnants of our solar system’s formation. Since its launch in 2021, Lucy has been traveling billions of miles through space to piece together the solar system’s early story.

The Origins of the Lucy Mission

Launched on October 16, 2021, from Cape Canaveral aboard an Atlas V 401 rocket, Lucy is the first mission specifically designed to explore the Jupiter Trojan asteroids — clusters of small celestial bodies that orbit the Sun in the same path as Jupiter, trapped in gravitationally stable regions called Lagrange points (L4 and L5).

These Trojans are thought to be leftovers from the formation of the outer planets, and scientists believe they could hold clues about the conditions in the early solar system, over 4 billion years ago.

The mission is led by NASA’s Goddard Space Flight Center, with spacecraft design and operations handled by Lockheed Martin.

Why Study the Trojan Asteroids?

The Trojan asteroids are special for several reasons:

They are relatively pristine compared to other asteroid populations.
They represent a diverse mix of asteroid types — varying in color, size, and composition.
They may contain organic materials and minerals that help explain how the planets, including Earth, came to be.

Lucy’s findings will help us understand how planets grew and how the current architecture of the solar system evolved.

Instruments Onboard Lucy

Lucy carries three primary scientific instruments:

L'Ralph: A color imager and infrared spectrometer that analyzes surface composition
L'LORRI: A high-resolution black-and-white camera designed to image surface detail
L'TES: A thermal sensor that maps surface temperature and heat flow

Additional tools include a terminal tracking camera and a high-gain antenna to send collected data back to Earth across billions of miles.

Mission Timeline: From Launch to the Asteroid Belt

2021–2023: Early Cruise Phase: Lucy completed a gravity assist maneuver around Earth in October 2022 to gain speed and adjust trajectory for future encounters.

April 20, 2025: First Flyby — Asteroid Donaldjohanson: Lucy’s first close asteroid flyby targeted (52246) Donaldjohanson, a 4-kilometer-wide asteroid in the main asteroid belt. It served as a systems test and scientific opportunity before reaching the more distant Trojans.

During the encounter, Lucy passed within about 960 kilometers of the asteroid while traveling over 48,000 kilometers per hour. The flyby helped calibrate instruments and gave scientists a first glimpse of the spacecraft’s ability to perform close flybys of small, fast-moving objects.

What Comes Next?

August 2027: Trojan Asteroid Flybys Begin: Lucy will reach the leading Trojan swarm (L4) and begin visiting its primary targets:

Eurybates (with satellite Queta)
Polymele
Leucus
Orus

2031: Second Earth Gravity Assist: Lucy will swing by Earth again to reposition for the next leg of its journey toward the trailing Trojan swarm (L5).

2033: Final Flyby — Patroclus and Menoetius: The final destination includes a rare binary Trojan system — two asteroids orbiting each other — which may provide insights into how small bodies formed in the early solar system.

Mission Significance

Lucy is groundbreaking in several ways:

It’s the first mission to visit so many asteroids with one spacecraft (eight in total).
It’s the first dedicated Trojan asteroid mission.
It will help us understand how materials were distributed across the solar system and how planets like Earth formed.

Latest Milestone: Donaldjohanson Flyby

On April 20, 2025, Lucy performed its first asteroid encounter. The mission team used this as a full test of Lucy’s tracking, targeting, and imaging capabilities. Data from this flyby is expected to be downlinked over the course of a week, providing early insights and validation of the mission’s systems.

Flyby Distance: ~960 kilometers

Speed: ~48,000 km/h

Asteroid Name: Donaldjohanson (named after the scientist who discovered the Lucy fossil)

Summary

NASA’s Lucy mission is a bold and ambitious effort to unlock the early history of our solar system. By visiting ancient Trojan asteroids, Lucy will help scientists understand the processes that shaped planets, including Earth.

For ongoing updates, visit NASA’s official Lucy mission page: https://science.nasa.gov/mission/lucy/