Planetary researchers at Southwest Research Institute has completed a study detailing how a proposed spacecraft could fly by an interstellar comet, providing remarkable insights into the properties of bodies originating beyond our Solar System. Using the recent discovery of the interstellar comet 3I/ATLAS, they validated the mission concept, determining that 3I/ATLAS could have been intercepted and observed by the proposed spacecraft.
Hubble captured this image of 3I/ATLAS on July 21, 2025, when the comet was 446 million km (277 million miles) from Earth. Image credit: NASA / ESA / David Jewitt, UCLA / Joseph DePasquale, STScI.
In 2017, the interstellar object 1I/‘Oumuamua became the first interstellar comet detected in the Solar System.
Its discovery was soon followed by the discovery of the second interstellar comet, 2I/Borisov in 2019, and now this year, 3I/ATLAS, which made worldwide headlines as it became the third officially recognized interstellar object to cross into our Solar System.
“These new kinds of objects offer humankind the first feasible opportunity to closely explore bodies formed in other star systems,” said lead author Dr. Alan Stern, a planetary scientist at Southwest Research Institute.
“An interstellar comet flyby could give unprecedented insights into the composition, structure and properties of these objects, and it would significantly expand our understanding of solid body formation processes in other star systems.”
Scientists estimate that numerous interstellar objects of extrasolar origin pass inside Earth’s orbit each year, and that as many as 10,000 pass inside Neptune’s orbit in any given year.
Dr. Stern and colleagues tackled the unique design challenges and defined the costs and payload needs associated with an interstellar comet mission.
The hyperbolic trajectories and high velocities of these objects preclude orbiting them with current technology, but the study showed that flyby reconnaissance is feasible and affordable.
“The trajectory of 3I/ATLAS is within the interceptable range of the mission we designed, and the scientific observations made during such a flyby would be groundbreaking,” said Southwest Research Institute’s Dr. Matthew Freeman.
“The proposed mission would be a high-speed, head-on flyby that would collect a large amount of valuable data and could also serve as a model for future missions to other interstellar comets.”
The authors established the major, comprehensive scientific objectives for a mission to an interstellar comet.
Determining the physical properties of the body would offer insights to its formation and evolution.
Examining the interstellar comet composition could help explain its origins and interpret how evolutionary forces have affected the comet since its formation.
Yet another objective is to thoroughly investigate the nature of the object’s coma, the escaping atmosphere emanating from its central body.
To develop mission trajectory options, the researchers developed software that generated a representative, synthetic population of interstellar comets then calculated a minimum energy trajectory from Earth to the path of each comet.
The software’s calculations showed that a low-energy rendezvous trajectory is possible, and in many cases, would require less launch and in-flight velocity change resources than many other solar system missions.
The scientists used this software to calculate the trajectory that the proposed spacecraft could have taken from Earth to intercept 3I/ATLAS.
They found that the mission could have reached 3I/ATLAS.
“The very encouraging thing about the appearance of 3I/ATLAS is that it further strengthens the case that our study for an interstellar comet mission made,” said Dr. Mark Tapley, an orbital mechanics expert at Southwest Research Institute.
“We demonstrated that it doesn’t take anything harder than the technologies and launch performance like missions that NASA has already flown to encounter these interstellar comets.”
