Interstellar objects offer a rare glimpse into planetary systems beyond our own, acting as cosmic time capsules carrying materials formed far from the Sun. The discovery of 3I/ATLAS presented a unique opportunity to study one of these visitors. Like other interstellar objects, it expels carbon dioxide and water vapor potentially dating back billions of years.
However, astronomers detected 3I/ATLAS relatively late in its journey, finding it within Jupiter’s orbit in July 2024 and traveling at over 60 kilometers per second. It reached its closest approach to the Sun in October and has been rapidly moving away into deep space ever since, leaving limited time to plan a direct mission from Earth. This rapid trajectory presents a significant challenge for observation and potential exploration.
The Challenge of Reaching an Interstellar Comet
Despite the difficulties, some scientists believe a mission to observe 3I/ATLAS up close remains technically possible. The proposal involves a high-risk, potentially groundbreaking endeavor that would push the boundaries of space engineering. A study led by Adam Hibberd of the Initiative for Interstellar Studies, along with Marshall Eubanks (Space Initiatives Inc.) and Andreas Hein (University of Luxembourg), suggests a theoretical window for intercepting the object still exists. The research – available as a pre-print on arXiv and submitted for publication in the Journal of the British Interplanetary Society – proposes a launch in 2035 that could reach 3I/ATLAS around 2085, as reported by Space.com.
By 2085, the comet would be more than 732 astronomical units from the Sun – 732 times the distance between Earth and our star – exceeding the distance Voyager 1 has traveled in nearly 48 years.
The Oberth Maneuver: Key to a Record-Breaking Mission
The proposed mission relies on the Oberth effect, formulated in 1929 by Hermann Oberth. The principle is simple: the faster a spacecraft is moving when its engines fire, the greater the impulse it receives. The plan involves using the Sun’s gravity as a slingshot, approaching the star and accelerating at the closest point of its trajectory – the perihelion – when its velocity is at its maximum.
“Practically all launches use the Oberth effect,” Eubanks told Space.com. “However, I don’t find any record of a direct maneuver like the one we’re proposing, with a significant rocket burn at the closest point during a flyby.”
For comparison, Space.com notes that Voyager 1 – the farthest human-made object – is currently about 170 astronomical units from the Sun after almost half a century of travel; intercepting 3I/ATLAS could occur at over 700 AU from our star.
The 2035 launch date is strategic, coinciding with the most favorable alignment between Earth, Jupiter, the Sun, and 3I/ATLAS, minimizing propulsion requirements and total flight time.
Extreme Technical Challenges: Solar Heat and Complex Trajectory
Approaching the Sun so closely presents significant challenges. The spacecraft would necessitate to pass the perihelion at just 3.2 solar radii from the Sun’s center and ignite its engines at that critical point, enduring extreme temperatures. This level of proximity demands advanced thermal protection systems.
As a reference, the Parker Solar Probe has withstood temperatures between 1370 and 1400 °C with its heat shield during its approaches to the Sun, though it didn’t get as close as the proposed mission. Researchers suggest using a carbon-composite heat shield with additional layers of aerogel to withstand similar conditions.
The proposed trajectory is also unconventional. Instead of heading directly for the object, the spacecraft would first fly towards Jupiter for approximately a year. There, it would use the gas giant’s gravity to slow down and redirect its trajectory towards the Sun; without this step, the spacecraft – already moving at Earth’s orbital speed of about 30 km/s – would simply continue orbiting in a wide path.
Following this gravitational braking would be the solar approach and the Oberth maneuver. Unlike the Parker Solar Probe – which used multiple Venus flybys to adjust its trajectory – the mission to 3I/ATLAS would have limited opportunities for such maneuvers due to the object’s high speed.
Alternatives and the Future of Interstellar Exploration
Beyond the mission’s feasibility, a key question remains: is pursuing 3I/ATLAS for decades worthwhile? This is a valid concern, especially considering the Vera C. Rubin Observatory, now operational in Chile, could detect around one interstellar comet per year, a significant increase from the three identified so far.
“We’ll have to wait and see what happens,” Eubanks told Space.com. “Perhaps after we’ve found, say, ten interstellar objects, 3I will seem commonplace and not worth organizing an expedition to chase after.”
the immense speeds involved would allow only a brief flyby, limiting the scientific return of such an ambitious undertaking.
some researchers believe developing alternative mission architectures is more promising: probes already positioned in space, ready to intercept interstellar visitors near the perihelion without the need for risky Oberth maneuvers. The European Space Agency (ESA) is planning to launch its Comet Interceptor mission in late 2028, which will “park” at the L2 Lagrange point, awaiting a suitable target. This approach could allow for more practical study of future interstellar visitors.
However, Oberth maneuvers shouldn’t be dismissed. They could prove useful for exploring trans-Neptunian objects, or even reaching the hypothetical Planet Nine, estimated to be between 290 and 800 astronomical units from the Sun.
“I’m fairly confident that when we develop the capability to reach these interstellar objects, there will be a strong desire to directly explore at least some of them,” Eubanks concluded.
For now, 3I/ATLAS continues to move away from the solar system into interstellar space, carrying clues about distant planetary systems. It may never be reached. Or perhaps, in many decades, a small Earth-based probe will intercept it to attempt to decipher them.
