Not only are we characterizing interstellar object 3I/ATLAS, we’re going meta:
Astrophysics > Earth and Planetary Astrophysics arxiv.org/abs/2510.13222
[Submitted on 16 Oct 2025]
Grant, S. R. Jones, G. H. Prospects for the Crossing of Comet 3I/ATLAS’s Ion Tail
arxiv.org/abs/2510.11779
[Submitted on 15 Oct 2025]
Hoogendam, W. B. Shappee, B. J. Wray, J. J. et al. Spatial Profiles of 3I/ATLAS CN and Ni Outgassing from Keck/KCWI Integral Field Spectroscopy
No spacecraft is in position, or out of position with a powerful propulsion system, to fly by 3I/ATLAS. At best, we have spacecraft with fair enough telescopic instruments, at fair enough distances. Sorry, it will take Comet Interceptor to chase down fleeting targets… and CI isn’t built and flown yet.
But… flying by a comet nucleus of is just one (main) approach. Comets by definition shed material, forming a coma and tail(s). Sampling the tail gets us a (biased) view of (a fraction of) a comet’s composition and processes. We now know that, depending on activity, some comet tails can stretch for multiple AUs- that is, partway across the inner Solar System. Ulysses saw this, multiple times.
Grant and Jones now determine that some built, flying spacecraft may be hit with 3I tail material. Possibly Europa Clipper, and maybe Hera, will happen to be in good position. So Europa Clipper may study a small Solar System body after all! Of course, this is no guarantee- a comet’s ion tail is blown outward by the solar wind, and that wind is neither straight nor steady. A ‘gust’ may send 3I’s tail in the wrong direction… or the right direction, multiple times. Such is space weather. Assuming typical solar wind states, Europa Clipper should be in place later this month, into November; Hera a bit later.
Hoogendam et al. then report their own observations, from the ground. Using the Keck Telescope’s KCWI instrument (Keck Cosmic Web Imager), they did their own cyanide and nickel measurements.
As I’ve mentioned before, these are arXiv posts– not to the same rigor and verification as I usually blog about. But note that both these paper topics are pretty straightforward. A trajectory and intersection analysis is just not weird; neither is a spectroscopic observation. I would be really surprised if all these authors screwed up in a fundamental way. Jones, for one, is Geraint H. Jones, from the Comet Interceptor project; if he can’t figure it out, then who can. Similarly, Hoogendam et al. are treading the same spectroscopic ground as the prior astronomers I’ve linked. Each of their papers serves as a cross-check on the others. If one team screwed up, the rest would go after them.