The Europa Clipper spacecraft is on a trajectory that may allow it to interact with the ion tail of the interstellar comet 3I/ATLAS. This event is anticipated to occur between October 30 and November 6, coinciding with the spacecraft”s alignment with the comet”s ion tail and the sun. Researchers from Europe have utilized computer modeling to forecast such alignments, providing a rare chance for direct sampling of material from an object beyond our solar system.
“Currently, we have minimal information regarding the interiors of interstellar comets and the star systems from which they originated,” stated Samuel Grant of the Finnish Meteorological Institute, who spearheaded the research. “This opportunity to sample the tail could yield invaluable insights into a different part of our galaxy.”
Despite the potential for groundbreaking discoveries, several challenges could hinder the Europa Clipper from detecting charged particles from 3I/ATLAS. A continuing U.S. government shutdown poses the risk of keeping the spacecraft in cruise mode, with many of its instruments inactivated. Should the shutdown persist, it remains uncertain if the team can activate the necessary instruments in time to gather data during the predicted alignment.
If successful, the measurements could reveal the composition of the interstellar comet, allowing comparisons with comets originating from our solar system.
Comets are characterized by two tails formed from dust and particles that are expelled from their surfaces due to thermal effects as they approach the sun. The dust tail, which is the more visible of the two, follows the comet”s path, while the ion tail, formed by charged particles ejected into the solar wind, always points away from the sun.
During the upcoming alignment, the Europa Clipper will be ideally positioned to capture some of these ions, which are propelled at high speeds by the solar wind. The ion tail of 3I/ATLAS can be seen in an image captured by the Gemini South Observatory.
In coordination with Grant, Geraint Jones from the European Space Agency has contributed to the predictive capabilities of their Tailcatcher program, which tracks solar wind movements. “By analyzing the velocity of the solar wind packets upon arrival, we can trace their path back to the sun and cross-reference it with the comet”s location,” explained Grant.
The researchers” calculations indicate that there exists a possibility for the Europa Clipper to intercept solar wind packets that have collected ions from the comet”s ion tail. Differentiating between solar wind ions and cometary ions is feasible through their chemical signatures, as cometary ions typically contain heavier species, particularly water-group ions.
Nevertheless, the successful detection of these ions depends on various factors, including the direction of the solar wind and its intensity at the time of the encounter. The comet will reach its closest point to the sun on October 29, while the Europa Clipper is currently positioned significantly farther away.
As 3I/ATLAS approaches the sun, its activity is expected to increase, which may enhance the probability of Europa Clipper detecting ions from the comet. Additionally, the European Space Agency”s Hera spacecraft will also be positioned to capture solar wind packets containing cometary ions during this timeframe, although it lacks the necessary instruments for such measurements.
Despite not being part of the Europa Clipper team, Grant and Jones have effectively utilized the Tailcatcher program to predict past ion tail crossings, including successful detections by the European Space Agency”s Solar Orbiter in 2020. This history of accurate predictions suggests that future opportunities for tail crossings will arise, potentially including new interstellar comets.
In 2029, the European Space Agency plans to launch the Comet Interceptor mission, which aims to closely study interstellar comets. Grant remarked, “The primary goal of the Comet Interceptor is to sample the coma and head of the tail of an interstellar or long-period comet, providing an exceptional opportunity for scientific exploration.”
The prediction of the ion tail crossing by Grant and Jones has been documented in a pre-print available on the arXiv pre-print server.
