We have the means today to fly a spacecraft by an interstellar object visiting our solar system, a new study concludes — and we could have done it already with comet 3I/ATLAS.
Flyby reconnaissance of interstellar objects is “feasible and affordable,” scientists with the Southwest Research Institute (SWRI), who led the study, said in a statement on Wednesday (Sept. 3).
“The trajectory of 3I/ATLAS is within the interceptable range of the mission we designed,” Matthew Freeman, the study project manager and director of space instrumentation at SWRI, said in the statement.
Unfortunately, however, getting a probe into orbit around objects like 3I/ATLAS for more detailed study isn’t currently possible, given how fast such visitors move relative to bodies native to our solar system. Interstellar objects are on “hyperbolic” trajectories, meaning that they are entering and exiting the neighborhood instead of circling our sun.
SWRI’s newly publicized mission idea is a proposal and does not imply that such a spacecraft will be funded by NASA or any other entity. But SWRI argues that laying the groundwork now would allow for scientists to one day access comets from other solar systems with relative ease — without leaving our neighborhood.
Flybys of interstellar objects would “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,” Alan Stern, SWRI associate vice president and leader of the study project, said in the same statement.
Stern is perhaps best known for being the principal investigator of NASA’s New Horizons mission, which was the first to fly by Pluto in 2015 before venturing on to do studies of other small bodies in the Kuiper Belt. (Stern also flew to suborbital space himself with Virgin Galactic in 2023, on a research-focused mission.)
Comet 3I/ATLAS is the third confirmed interstellar object to pass through our solar system, following the discovery of 1I/’Oumuamua in 2017 and 2I/Borisov in 2019. (The “I” in each of these names stands for “interstellar”, while each of the numbers preceding their names indicates the order of discovery.)
Interstellar visitors have been hard to spot so far, but more capabilities are coming online quickly. SWRI said that newer all-sky surveyors such as the National Science Foundation’s Vera C. Rubin Observatory may make interstellar finds more common within a decade.
The new SWRI statement said that “numerous” interstellar objects safely pass inside the orbit of Earth every year, while “as many as 10,000” come within the orbit of Neptune, which is roughly 30 times farther from the sun than our own planet. (Earth’s distance is roughly 93 million miles, or 150 million kilometers, from the sun.)
Given these parameters, SWRI created software that made a representative but artificial population of interstellar objects. The software then calculated how much energy it would take a spacecraft to leave Earth and approach each object.
Flybys are not only feasible, the study showed, but “in many cases, would require less launch and in-flight velocity change resources than many other solar system missions,” the statement noted. Costs and payloads were then estimated, with the notion that a mission concept “could be later proposed to NASA.” (The SWRI statement did not provide details about likely mission costs, and the study is internal to the organization; it apparently has not been submitted for publication in a journal.)
A future spacecraft could be tasked with a science agenda such as looking at the interstellar body’s physical properties to learn more about how it formed and evolved, or examining the object’s composition to learn more about where it came from. Another investigation could look at the coma, or the loose “exosphere” of material sublimating from interstellar comets as they get closer to the heat and pressure of the sun.
The recent arrival of 3I/ATLAS “further strengthens the case” for visiting interstellar objects, according to Mark Tapely, an orbital mechanics specialist at SWRI. “We demonstrated that it doesn’t take anything harder than the technologies and launch performance [for] missions that NASA has already flown,” Tapley said.
