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Since 2017, three interstellar objects have been spotted passing through our solar system: 1I/ʻOumuamua, 2I/Borisov… and just this month, 3I/ATLAS. Discovered on July 1 by the Asteroid Terrestrial-Impact Last Alert Survey, 3I/ATLAS is zipping through the inner solar system in the last half of 2025.

Certainly, all assets on the ground and in space will be turned toward 3I/ATLAS over the next few frenzied months, to glean what we can… but what would 3I/ATLAS look like up close? Can we even consider chasing down such a speedy visitor?

Thus far, we've discerned that 3I/ATLAS is a very old object hailing from the thick galactic disk of the Milky Way galaxy, worthy of further study. Gemini North gave us a close-up view earlier mid-month, showing the object is definitely cometary in nature. Currently shining at +17th magnitude as it crosses the constellation Ophiuchus, expect 3I/ATLAS to brighten a hundredfold and reach +12th magnitude as it crosses perihelion 1.356 astronomical units (AU) from the sun on October 29th.

Unlike 1I/ʻOumuamua, we're seeing 3I/ATLAS while it's still on its inbound leg. Still, it's really truckin' along, moving at a speedy 58 kilometers per second relative to the sun. Could we catch up to it with existing technology? A on the arXiv preprint server out of Michigan State University titled "The Feasibility of a Spacecraft Flyby with the Third Interstellar Object 3I/ATLAS from Earth or Mars" is an interesting thought experiment on the prospect. The study could serve as a template for a future flyby of one of these enigmatic objects.

"A close flyby enables measurements that are not achievable from Earth-based telescopes," lead author on the paper Atsuhiro Yaginuma (Michigan State University) told Universe Today. "For example, we could obtain direct compositional and isotopic analysis of ices, dust, and organics in situ.

"We could also obtain high-resolution imaging of the nucleus and get key information regarding its shape, size, spin state, and active jets. All of these could yield critical insights into planetary formation and evolution—and the delivery of volatiles and organics to potentially habitable planets—in an alien system."

Chasing an object like 3I/ATLAS would entail a whirlwind mission. The study looked at various scenarios, with an Earth or Mars departure in the January 2025 through March 2026 time frame. Earth departure would require a high initial delta-V of 24 kilometers per second to attain an optimal path.

The Dawn spacecraft nearly matched this, with a post-launch delta-V of nearly 23 kilometers per second. In contrast, Mars delta-V would have only needed a change of 5 kilometers per second in early 2025 to catch 3I/ATLAS. The energy budget for any mission goes up sharply, the longer you wait to launch.

Mars was looked at as an optimal alternate launch point because 3I/ATLAS makes a close 0.2 AU (29 million kilometers) pass versus the Red Planet on October 3rd. Closest Earth passage for 3I/ATLAS is less favorable, at 1.8 AU distant on December 19th.

"Mars orbiters can image 3I/ATLAS, and obtaining scientific images would be very helpful for learning about the object, especially around perihelion while we can't observe 3I/ATLAS from Earth," says Yaginuma.

"It depends on each mission, but having high-resolution images would be beneficial. It's critical to observe comets during their perihelion—when they are closest to the sun—and 3I/ATLAS won't be observable from Earth then. So Mars offers one of our only opportunities to observe the interstellar interloper at all when it should have the most activity."

Of course, the pipeline of getting a mission from planning to the launch pad is a long one. This would also mean that a heavy lift carrier such as NASA's Space Launch System (SLS), SpaceX's Falcon Heavy or China's Long March 5 would have to be repurposed for a single, one-shot flyby mission.

NASA's MAVEN, Odyssey, Mars Reconnaissance Orbiter (MRO) and ESA's Trace Gas Orbiter and Mars Express are all currently operational and in orbit around the Red Planet.

"A Mars-based intercept requiring a delta-V of 10 kilometers per second may be within current propulsion limits. In principle, these orbiters could use their remaining fuel to shift into a 3I/ATLAS flyby trajectory, turning their end-of-life maneuvers into a rare scientific opportunity," says Yaginuma. "If one of them is approved and has enough remaining fuel, such a flyby would be valuable."

The study also looked at repurposing missions already built, now looking for a new destination. One such orphaned mission is the Joint Advanced Propulsion Institute (Janus) duo. Janus is a 36-kilogram pair of SIMPLEx spacecraft, which were set to launch with the Psyche mission to study asteroids 1996 Fg3 and 1991 VH. The two Janus spacecraft were shelved when delays forced Psyche to take an alternate orbital path to its primary objective, metallic asteroid 16 Psyche.

"What we showed in the paper is that there would be a steep rocket fuel requirement to launch a spacecraft from Earth to 3I/ATLAS," says Yaginuma. "JANUS is one of the ready-to-launch spacecraft that was going to visit binary asteroids but recently was shelved. JANUS is also a small spacecraft and relatively light, so we might be able to get it to 3I/ATLAS if we went sooner rather than later."

Another noted mission that's already underway is OSIRIS-APEX. This is NASA's OSIRIS-REX asteroid sample return mission, now repurposed for a flyby of the Near-Earth Asteroid 99942 Apophis in 2029. OSIRIS-APEX is set to perform an Earth gravity assist flyby in September 2025, and could make long-range observations of 3I/ATLAS using its MapCam and PolyCam imagers starting in November.

Most of the dates mentioned in the study have already come and gone, making the idea of launching an intercept mission after 3I/ATLAS more of an academic exercise at this point. To complicate such a hypothetical mission even further, flyby speeds in excess of 60 kilometers a second would make imaging during such a fast encounter tricky. For comparison, NASA's New Horizons spacecraft passed the Pluto-Charon system at 14 kilometers per second a decade ago in July 2015.

Future missions may make such a high-speed flyby a reality. The European Space Agency's proposed Comet Interceptor is an F-Class mission that would park at the sun-Earth L2 point and await a target. In a multi-spacecraft configuration optimized for multi-point observations, Comet Interceptor could chase down a new comet, and potentially even catch up to an interstellar object. Comet Interceptor is planned to launch in 2029.

"Once a suitable target is found, it (Comet Interceptor) will rendezvous and release two small probes to surround and study the comet from different angles at the same time," says Yaginuma.

"Its fuel and engines are designed for long-period comets, so if an interstellar object happens to pass near it, this could be one of our best opportunities for a close encounter. However, studies have shown that we would have to be pretty lucky to get an interstellar visitor as a feasible target for Comet Interceptor."

The bottom line takeaway from the study is the earlier that we can spot incoming interstellar objects, the more options we'll have available, and the less energy will be required to go after them. To this end, a new generation of all-sky surveys such as the recently commissioned Vera C. Rubin Observatory are promising to spot these incoming space rocks early, in an effort to study a new population of intriguing astronomical objects like never before.