The idea of alien probes wandering the cosmos may sound strange, but humans sent out a few ourselves in the 1970s. Both Voyager 1 and 2 have officially left our Solar System, and Pioneer 10 and 11 are not far behind.

So it’s not a stretch to think that alien civilisations – if they exist – would have launched their own galactic explorers.

However, this brings us to a crucial question: short of little green men popping out to say hello, how would we actually know if 3I/ATLAS, or any other interstellar object, was an alien probe?

We may never know

Without clear signs one way or the other, however, it may be impossible to know if some interstellar objects are natural or alien-made.

Objects like 3I/ATLAS remind us that space is vast, strange, and full of surprises. Most of them have natural explanations. But the strangest objects are worth a second look.

For now, 3I/ATLAS is likely just an unusually fast, old and icy visitor from a distant system. But it also serves as a test case: a chance to refine the way we search, observe and ask questions about the universe.