Exiled interstellar visitors like comet 3I/ATLAS are time capsules from the cosmos at large, yeeted from their exosolar homes by an unknown cataclysm and forced to drift through lonely space for billions of years, perhaps.
If they're lucky, they may cross paths with another star, such as the Sun, and warm themselves at our solar hearth for a short while before speeding back out into darkness.
This is lucky for us, too, since we get an unprecedented look at a chunk of an alien Solar System, which may have formed long before ours with chemistry unlike anything glimpsed before.
In fact, the exosolar system that formed 3I/ATLAS may have assembled it more than 7 billion years before our Sun ignited into life – possibly even before 3I/ATLAS's own star erupted.
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