When I saw the headline from NASA that the JWST found “clues to ancient, distant origin of comet 3I/ATLAS,” the interstellar comet which hurtled through the solar system last year and which I used as a case study in a post on the feasibility of conducting a rendezvous with such an object, I was rather excited. I thought it was reporting on an effort to astrodynamically trace back the comet’s trajectory in an effort to determine from where in the galaxy it originated. Doing so successfully with any kind of resolution is probably beyond any data and technology to which we have access – there are just too many variables and unknowns and n-body interactions involved – but it would nonetheless be a fascinating exercise.
The actual findings are a bit less interesting. The NASA article reports on a scientific paper which used JWST’s near infrared spectrometer to measure the isotopic composition of 3I/ATLAS, and then compared the results with our own and other observed solar systems’ isotopic compositions. Based on this effort, the authors were able to determine what the ancient solar system from which the comet originated might have been like (cold, cloudy, far away, and very, very old). It turns out that, based on the proportion of deuterium and carbon-12 in the comet, it might be some 12B years old, which is more than twice as old as our own solar system and means it formed when the universe was barely 2B years old.
These interstellar comets represent rare opportunities to gain insights into distant regions we can’t otherwise directly access to investigate. In this case, it seems they can also be an opportunity to gain insight into distant times. 3I/ATLAS is like a preserved time capsule shot through the galaxy from billions of years ago, telling us about a time and a place we can never go, but we get to experience a tiny sliver of it through studying the comet. It reminds me a bit of that Star Trek: The Next Generation episode where the time capsule spacecraft causes Captain Picard to relive the experience of an otherwise extinct civilization.
Given the number of observations which we conducted as the comet made its closest approach, I’m sure we will be seeing more studies and papers coming out about it in the coming months and years. Until we can visit other star systems with our own probes or in person, interstellar objects flying through the solar system are our only way to directly interact with and observe evidence of those environments. No wonder we find them so fascinating. Perhaps there are even now fragments of comets or asteroids from our own solar system set adrift through the cosmos to one day pass through the sensor network of some alien civilization.
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