[zelon88]

I believe that we've probably altered the geography of Earth to an extent that it would be trivially easy to determine from great distance that it was once inhabited by intelligent beings. Even if all of our cities are gone, the mineral deposits left behind would be so concentrated. Nevermind the nuclear endeavors.

We were able to detect dinosaurs on our own planet 65 million years after they went extinct, and they didn't even pollute anything.

[sjy]

I recommend Schmidt and Frank’s article on the Silurian hypothesis [1] for a surprisingly different take on this. The full text is on arXiv [2]. “We summarize the likely geological fingerprint of the Anthropocene, and demonstrate that while clear, it will not differ greatly in many respects from other known events in the geological record” – that is, the record we can observe from a distance of zero!

[1] https://en.wikipedia.org/wiki/Silurian_hypothesis

[2] https://arxiv.org/abs/1804.03748