What Happens If Hera and Europa Clipper Fly Through the Tail of 3I/ATLAS?
Hera and Europa Clipper May Cross Paths with Interstellar Comet 3I/ATLAS’ Tail
An Unexpected Opportunity: Two Spacecraft, One Interstellar Encounter
Could two of humanity’s spacecraft unintentionally become the first to study the tail of an interstellar comet? That’s the fascinating possibility raised by a new study from Samuel Grand and Geraint Jones of the Finnish Meteorological Institute and the European Space Agency (ESA).
Their paper, accepted for publication in the Research Notes of the American Astronomical Society, suggests that ESA’s Hera mission and NASA’s Europa Clipper could both pass through the ion-rich tail of 3I/ATLAS — only the third interstellar object ever discovered.
While conspiracy theories have swirled around 3I/ATLAS since its discovery — from alien probes to cosmic omens — this proposal stands out as a serious scientific opportunity.
Interstellar Visitor 3I/ATLAS: A Cosmic Wanderer with a Growing Tail
Since its discovery in early June, 3I/ATLAS has grown increasingly active as it approaches the Sun. Astronomers have reported “gushing” water vapor and a dramatic increase in the size of its cometary tail. That tail, composed of gas, dust, and charged ions, stretches millions of kilometers across space — a diffuse but detectable trail left behind as the comet races toward its closest approach to the Sun, or perihelion, on October 29th.
However, as 3I/ATLAS moves deeper into the inner Solar System, it has also drifted out of the reach of Earth-based telescopes. That’s why leveraging existing spacecraft already en route elsewhere may be our best shot to learn more about it.
Hera and Europa Clipper: Two Missions, One Cosmic Coincidence
Both Hera and Europa Clipper were designed for entirely different missions — yet fate may have aligned them for an extraordinary interstellar encounter.
Hera, an ESA mission, is traveling to the Didymos–Dimorphos binary asteroid system, the site of NASA’s 2022 DART impact test that demonstrated asteroid deflection.
Europa Clipper, bound for Jupiter’s icy moon Europa, will explore its frozen surface and subsurface ocean in search of conditions that could support life.
By pure chance, both spacecraft will pass “downwind” of 3I/ATLAS in the coming weeks:
Hera between October 25 and November 1
Europa Clipper between October 30 and November 6
Could these overlapping flight paths allow scientists to detect traces of an interstellar comet’s tail for the first time in history?
Modeling the Encounter: The “Tailcatcher” Simulation
Predicting whether the spacecraft will truly intersect the comet’s tail is not straightforward. Solar wind — the constant stream of charged particles emitted by the Sun — bends and pushes comet tails into long, curved arcs.
To estimate where 3I/ATLAS’ tail might reach, Grand and Jones used a model called “Tailcatcher.” This simulation maps how solar wind speed affects the position of ions shed from the comet. By comparing these predictions with the flight paths of Hera and Europa Clipper, the researchers calculated a “minimum miss distance” for each craft relative to the tail’s central axis.
Even under optimistic assumptions, both spacecraft will pass millions of kilometers from the comet’s main axis — about 8.2 million km for Hera and 8 million km for Europa Clipper. Yet, for a comet as active as 3I/ATLAS, its ion cloud could easily extend that far.
Can They Detect Interstellar Ions? Instrument Capabilities and Limitations
Not all spacecraft are created equal when it comes to studying charged particles in space. Hera, unfortunately, lacks instruments sensitive enough to detect ions or to measure the magnetic draping effect — the way a comet’s coma distorts the solar wind’s magnetic field.
Europa Clipper, however, is far better equipped. Its plasma instrument and magnetometer could directly detect those subtle changes in particle composition and field orientation — effectively sampling the chemistry and physics of an interstellar object.
Still, the challenge remains: can these missions be reoriented, even slightly, in time?
Racing Against Time: Can Mission Teams Respond Fast Enough?
Space operations rarely allow for improvisation, especially when it comes to missions already traveling on precise interplanetary trajectories. With only a few weeks’ notice, mission controllers would need to assess feasibility, safety, and data return potential before any adjustments could be made.
Will they act quickly enough? And if they do, could Europa Clipper and Hera become the first spacecraft to directly sample the tail of an interstellar comet — an achievement that would come entirely by accident?
A Rare Chance for Serendipitous Science
Science often advances not through perfect planning, but through seizing rare opportunities. The alignment of Hera, Europa Clipper, and 3I/ATLAS offers a fleeting but historic chance to observe interstellar material interacting with our Solar System.
If mission teams respond in time, their instruments could capture the first in-situ data from a comet that came from beyond our Sun’s gravitational reach — a record of alien dust and ions drifting through the void.
Could this unplanned encounter rewrite what we know about interstellar visitors — or even reveal how material from distant star systems behaves in our own cosmic neighborhood?
Source: What Happens If Hera and Europa Clipper Fly Through the Tail of 3I/ATLAS?
What If SETI Actually Finds Aliens—Who Speaks for Earth?
What Happens If Hera and Europa Clipper Fly Through the Tail of 3I/ATLAS?