Source: NASA
Space exploration often brings unexpected opportunities. NASA has considered redirecting its Juno spacecraft to encounter a rare interstellar object known as 3I/ATLAS. This comet-like visitor from beyond the solar system passes close to Jupiter in early 2026. If approved, the flyby would mark the first time a spacecraft studies an object from another star system up close. The plan extends Juno’s mission, which focuses on Jupiter, to gather data on this distant traveler.
Interstellar objects originate outside the solar system. They form around other stars and get ejected into space, wandering through the galaxy until gravity pulls them into another system like ours. These objects offer clues about distant planetary systems and their building blocks.
The first known interstellar object, ʻOumuamua, appeared in 2017. It had a cigar-like shape and moved at high speed, puzzling scientists with its unusual acceleration. The second, 2I/Borisov, discovered in 2019, resembled a comet with a tail of gas and dust. Both passed through the inner solar system too quickly for spacecraft to reach them.
3I/ATLAS joins this group as the third confirmed interstellar visitor. Its path shows it doesn’t orbit the sun, confirming its origins elsewhere.
Astronomers spotted 3I/ATLAS on July 1, 2025, using the Asteroid Terrestrial-impact Last Alert System in Chile. Also called C/2025 N1 (ATLAS), it travels at about 60 kilometers per second. Its orbit is hyperbolic, with an eccentricity around 6.1, meaning it swings around the sun and then exits the solar system.
The object reaches its closest point to the sun, or perihelion, at about 1.36 astronomical units in late October 2025. Observations from the Hubble Space Telescope reveal a nucleus smaller than 2.8 kilometers in radius, surrounded by a coma of dust. As it approaches the sun, heat causes material to vaporize, creating this active envelope.
This discovery came with little warning, highlighting the need for quick responses in space missions.
Juno launched in 2011 and arrived at Jupiter in 2016. Its primary goal involves studying the planet’s atmosphere, magnetic field, and interior structure. The spacecraft spins to maintain stability and carries solar panels for power, a first for a mission so far from the sun.
Over the years, Juno has completed numerous orbits, capturing images of Jupiter’s poles and moons. The mission extended beyond its original end date, allowing more flybys of moons like Io and Europa. Now in its extended phase, Juno faces an eventual disposal by plunging into Jupiter’s atmosphere to avoid contaminating nearby moons.
The spacecraft’s position around Jupiter makes it ideal for this new opportunity, as 3I/ATLAS passes within 0.358 astronomical units of the planet.
Scientists have outlined a plan to adjust Juno’s trajectory for an intercept on March 14, 2026. This involves a maneuver in mid-September 2025, using a gravity assist from Jupiter to boost speed and change direction. The flyby would happen about 53.6 million kilometers from Jupiter.
Instead of ending the mission soon after, Juno would continue operating to approach 3I/ATLAS. The relative speed during the encounter would allow a brief but valuable observation window. No new launch is needed, saving time and resources compared to starting a dedicated mission from Earth.
Other spacecraft, such as the European Space Agency’s Jupiter Icy Moons Explorer or those orbiting Mars, have been considered, but Juno’s location offers the best chance.
Juno equips several tools suited for studying 3I/ATLAS. A near-infrared spectrometer can analyze the object’s surface composition by measuring light reflections. The magnetometer might detect any magnetic properties, while the microwave radiometer could sense thermal emissions.
An ultraviolet spectrograph would examine gases in the coma, revealing chemical makeup. The visible light camera, though designed for Jupiter’s clouds, can capture images of the nucleus and tail. Energetic particle detectors and plasma sensors might pick up interactions with the solar wind.
Data from these instruments would transmit back to Earth, providing the first detailed look at an interstellar object’s features.
Juno’s age presents hurdles. After over a decade in space, it has endured radiation from Jupiter’s belts, leading to occasional glitches that engineers have fixed. Fuel levels are low, and engine performance isn’t perfect, making precise maneuvers risky.
The short timeline adds pressure, with decisions needed soon to execute the trajectory change. Astrodynamics limit options, as altering a spacecraft’s path requires exact calculations. Despite these issues, software models show the intercept is possible with minimal adjustments.
If Juno can’t perform the flyby, opportunities with other probes remain limited due to the object’s speed and path.
A successful flyby would reveal much about 3I/ATLAS. Its composition might differ from solar system comets, showing variations in elements or isotopes formed under another star. The dust coma could indicate activity levels and material loss as it heats up.
Understanding its shape and structure would compare to ʻOumuamua and Borisov, building a picture of interstellar diversity. Such data helps model how planets form around other stars and what materials travel between systems.
This mission could set a precedent for repurposing existing spacecraft for surprise visitors. Upcoming projects, like the European Space Agency’s Comet Interceptor set for launch in 2029, aim to wait in space for similar objects. Improved surveys, such as the Legacy Survey of Space and Time, will detect interstellar intruders earlier, giving more preparation time.
As detection technology advances, encounters with these cosmic wanderers will become more common, expanding knowledge of the galaxy.
NASA’s potential use of Juno to fly by 3I/ATLAS represents an adaptive approach to space science. The interstellar object’s discovery opens a window to study extrasolar materials directly. While challenges exist, the rewards include unique data on distant origins. This effort underscores the value of flexibility in ongoing missions.
