Fast-moving objects like interstellar comet 3I/ATLAS may be planet-forming seeds, potentially helping to solve an old Solar System mystery. The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

On July 1, 2025, astronomers spotted an object moving through the Solar System at nearly twice the velocity of previous interstellar visitors ‘Oumuamua and Comet Borisov. The object, which was confirmed to be an interstellar comet with its own dusty coma, is far larger than the previous two, with an estimated nucleus (the rocky part of the comet, excluding its coma) of around 5.6 kilometers ( 3.5 miles ).

Early work showed that it is of huge interest to scientists, beyond being the third confirmed interstellar visitor. For a start, it may have

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