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Based on spectroscopic data obtained by the Webb Space Telescope in the past year as interstellar Comet 3I/Atlas zipped through our solar system, a team of scientists have now concluded that its make-up suggests it is extremely old, as much as 12 billion years old, which means it was formed in the very early universe not that long after the Big Bang.

You can read their paper here [pdf]. The graph to the right was published by NASA of the infrared spectroscopic data produced by the Webb Space Telescope that supports this conclusion. That data shows the comet was lacking in isotopes commonly found today, while enriched in isotopes expected only in the early universe. From the paper’s abstract:

[W]e report isotopic measurements of the interstellar comet 3I/ATLAS, which reveal an elemental composition unlike any Solar System body. The water in 3I/ATLAS is enriched in deuterium, at a level of D/H = (0.98 ± 0.06)%, which is more than an order of magnitude higher than in known comets, while its range of 12[Carbon]/13[Carbon] ratios (141–191 for CO2 and 123–172 for CO) exceeds typical values found in the Solar System, as well as nearby interstellar clouds and protoplanetary disks.

Such extreme isotopic signatures indicate formation at temperatures ≲ 30 K in a relatively metal-poor environment. When interpreted with respect to models for Galactic chemical evolution, the carbon isotopic composition implies that 3I/ATLAS may have accreted as long ago as 12 billion years, following a period of intense, early star formation. 3I/ATLAS thus represents a preserved fragment of an ancient planetary system.

As the scientists add in what I think is an understatement, “Its distant origin in space and time makes 3I/ATLAS a uniquely-valuable object studies tool for Galactic archaeology.”

That the comet is still remarkable similar in many other ways to comets in our solar system also tells us that the formation processes that form all solar systems are somewhat common. The solar system in which Comet 3I/Atlas formed was different from ours only that it formed when the universe was young, and thus somewhat different in make-up. Otherwise the processes were the same.

At the same time, Comet 3I/Atlas has given us a window into the early universe, and suggests future interstellar comets will do the same. And there will be future interstellar comets, because we are now developing the observational tools to see them as they routinely fly past on a regular basis.