Here's a fun one. We find an archive. Stored in a form durable enough to last eternity, we find a vault, the last remnant of some long-forgotten Martian civilization.

They include the usual history, culture, historical artifacts, etc. But what shocks our explorers most of all? The biological archive. DNA sequences, freeze dried tissue samples, etc. Their language, once cracked, reveals the truth.

This isn't just a library or archive to remember the Martians. They knew they were on a slowly dying world. They never got rocket technology, though they did master advanced biology before the end. So they included everything needed to revive them, to actually bring them back from the dead.

Then we have to figure out what to do. This isn't the dodo bird or some other species we, humanity, are responsible for killing off. The Martians died of natural causes a billion years before our ancestors crawled out of the water. We have no ancestral moral debt to the Martians.

Sure, we could bring them back. But think through the implications of that. Mars is their world, the very planet we were planning to colonize. Will they want it back, maybe ask to live on Earth in the millennia it takes to teraform it? And even then, we'll now have a literal alien civilian right on our doorstep. Do we really want to open that Pandora's Box?

I was introduced to the concept of the moral dilemma of bringing back extinct aliens from Isaac Arthur, and it's a scenario I truly love.