NASA Spacecraft Becomes First to Enter Jupiter’s Trojan Asteroid Region

NASA’s Lucy spacecraft has reached the region of space occupied by Jupiter’s Trojan asteroids, becoming the first spacecraft to enter this previously unexplored population of primitive solar-system bodies. The milestone came on October 28, 2026, after Lucy travelled more than 2.2 billion miles since its launch on October 16, 2021.

The achievement does not mean Lucy has already visited an asteroid. The spacecraft is approaching the leading Trojan group near Jupiter’s L4 Lagrange point, and its first close encounter, with the asteroid Eurybates, is scheduled for August 11, 2027. The mission will eventually explore eight Trojan asteroids, offering scientists an opportunity to investigate material that could preserve clues about how the solar system formed.

Key Takeaways

• NASA’s Lucy spacecraft reached Jupiter’s Trojan asteroid region on October 28, 2026.
• It is the first spacecraft to enter this region of primitive solar-system bodies.
• Lucy has travelled more than 2.2 billion miles since launching in October 2021.
• The spacecraft is approaching Jupiter’s leading Trojan group near Lagrange point L4.
• Its first Trojan asteroid flyby, Eurybates, is scheduled for August 11, 2027.
• Lucy will study eight Trojan asteroids through a series of close encounters.
• The mission could help scientists understand how the solar system formed approximately 4.5 billion years ago.
• The mission is expected to continue through its final Trojan encounter in March 2033.

What Are Jupiter’s Trojan Asteroids?

Jupiter’s Trojan asteroids are groups of space rocks that travel around the Sun along the same orbital path as the giant planet.

They are concentrated in two large groups located near special gravitational positions known as Lagrange points.

The first group occupies the L4 region, which travels ahead of Jupiter in its orbit. The second group occupies the L5 region, which follows behind the planet.

These locations are relatively stable because of the combined gravitational influence of the Sun and Jupiter.

The two groups are sometimes described as two islands of stability. They contain thousands of asteroids that have remained associated with Jupiter’s orbit over extremely long periods.

NASA estimates that the Trojan groups are approximately 484 million miles from Jupiter, roughly the same distance as Jupiter is from the Sun.

Despite the large number of asteroids in these regions, they are widely separated. The average distance between individual objects is more than six million miles.

Scientists believe these asteroids could contain relatively primitive material left over from the early stages of solar-system formation.

Why Is NASA’s Lucy Mission Important?

The Lucy mission was developed to investigate the origins and evolution of the solar system.

Scientists believe Jupiter’s Trojan asteroids may preserve important information about the material that existed when the planets formed around 4.5 billion years ago.

Studying their composition, surfaces, shapes and geological characteristics could help researchers understand how planetary building blocks were distributed and how the giant planets reached their current positions.

Until Lucy, no spacecraft had travelled specifically into the Jupiter Trojan regions to conduct close-up investigations.

The mission is designed to visit eight Trojan asteroids, including a binary pair consisting of Patroclus and Menoetius.

Rather than orbiting one asteroid, Lucy will perform a sequence of high-speed flybys, collecting scientific observations during relatively short encounters.

The mission also includes two earlier encounters with asteroids in the main asteroid belt.

How Did Lucy Reach the Trojan Asteroid Region?

NASA launched Lucy on October 16, 2021, from Cape Canaveral Space Force Station in Florida.

The spacecraft follows a complex trajectory involving multiple encounters with Earth to adjust its orbit and build the momentum needed to travel towards the Trojan asteroids.

These manoeuvres are known as gravity assists.

During a gravity assist, a spacecraft uses the gravitational influence of a planet to change its speed and direction relative to the Sun. This technique helps missions travel long distances without requiring enormous amounts of additional fuel.

Lucy has already completed two asteroid encounters:

• Dinkinesh: Lucy flew past this main-belt asteroid on November 1, 2023, and discovered its small companion, Selam.
• Donaldjohanson: The spacecraft completed a flyby on April 20, 2025, collecting observations of another main-belt asteroid.

These encounters helped NASA test the spacecraft’s instruments and prepare its team for the more distant Trojan investigations.

After travelling more than 2.2 billion miles, Lucy reached the region surrounding Jupiter’s leading Trojan population in October 2026.

Which Asteroids Will Lucy Explore Next?

Lucy has a long sequence of encounters planned before completing its mission.

Its first Trojan target will be Eurybates, followed by several other asteroids in the leading group.

Asteroid	Planned encounter
Eurybates and its moon Queta	August 11, 2027
Polymele	September 14, 2027
Leucus	April 18, 2028
Orus	November 11, 2028
Patroclus and Menoetius	March 3, 2033

The first encounter with Eurybates will be particularly important because it will provide the mission’s first close-up observations of a Jupiter Trojan asteroid.

Lucy will spend only a few hours studying the asteroid during its high-speed flyby.

After completing its first four Trojan encounters, the spacecraft will return towards Earth in 2030 for a third and final gravity assist.

That manoeuvre will redirect Lucy towards Jupiter’s trailing Trojan group, where it is scheduled to investigate the binary asteroid pair Patroclus and Menoetius in March 2033.

How Will Lucy Study the Asteroids?

Lucy carries several scientific instruments designed to investigate the physical and chemical characteristics of its targets.

Its equipment includes cameras, infrared instruments and a system for measuring the surface temperatures and compositions of the asteroids.

One of its main imaging instruments is L’Ralph, which includes a colour visible-imaging camera and an infrared imaging spectrometer.

Another important instrument is L’LORRI, a high-resolution camera used to capture detailed images of distant targets.

The spacecraft also carries the Thermal Emission Spectrometer, which measures infrared radiation to help scientists understand surface properties.

These instruments will help researchers investigate:

• Surface composition and mineral characteristics.
• Asteroid shapes, sizes and geological features.
• Surface temperatures and thermal properties.
• The presence of smaller moons or companion objects.
• Differences between individual Trojan asteroids.

NASA has already begun camera tests using distant observations of Lucy’s future targets. These tests help the mission team prepare the instruments and select appropriate settings for the upcoming encounters.

Why the Mission Could Change Our Understanding of the Solar System

The Trojan asteroids are interesting because they may preserve material from the early solar system.

Planetary scientists believe that the giant planets underwent significant changes in their positions during the solar system’s early history.

The locations and characteristics of the Trojan populations could provide evidence that helps test theories about those movements.

For example, researchers want to understand whether these asteroids formed near their current positions or were captured from other regions during the early evolution of the planets.

Studying multiple asteroids is particularly valuable because the Trojan population is not necessarily made up of identical objects.

Differences in their composition and physical characteristics could reveal that they originated in different environments.

Lucy could therefore provide information about both individual asteroids and the broader processes that shaped the solar system.

The Bigger Picture

NASA’s Lucy mission represents a major step in the exploration of small bodies beyond the main asteroid belt.

While spacecraft have previously visited Jupiter and explored asteroids closer to Earth, the Trojan populations have remained largely unexplored at close range.

The mission could help scientists improve their understanding of planetary formation, the movement of material through the early solar system and the origins of the giant planets.

Its findings may also provide a valuable comparison with observations from other asteroid missions, including NASA’s OSIRIS-REx and Japan’s Hayabusa missions.

Looking Ahead

The next major milestone will be Lucy’s encounter with Eurybates in August 2027. Scientists will use the spacecraft’s instruments to collect close-up images and measurements, beginning a series of investigations that will continue through the following years. The spacecraft and its instruments are currently reported to be operating as expected.

The mission’s final Trojan encounter is scheduled for March 2033, when Lucy will study Patroclus and Menoetius. If the spacecraft completes its planned journey, scientists will have observations of eight Trojan asteroids, providing a new body of evidence about the ancient objects that share Jupiter’s orbit.