Extinct Alien Species
The Isaac Arthur video above is about one of the most pessimistic but also arguably the most likely reason why there's no solid evidence for life on other planets: Civilizations inevitably die and there is nothing that survives. At the end of this post I'll also link a video clip from Carl Sagan's Cosmos series featuring the Drake equation. The math is demonstrated to dramatically come to the possible conclusion that Earth life might be all there is in this part of the Universe. It is also good to see the Arecibo telescope in the video considering the Arecibo telescope was decommissioned and collapsed late last year.
In the video Isaac Arthur gives the hypothetical scenario that evidence gets discovered by space colonists of an extinct alien species once living on a planet around 82 G. Eridani 20 light years from Earth. The colonists in the scenario name the planet Amber and the moon orbiting Amber was named Shiva. On Shiva a chain of evidence leads to it being inferred that something catastrophic happened on Amber a few million years ago and the planet is now covered in ice. On Shiva a moonbase is discovered and it was clear that the aliens were stranded on Shiva with only enough supplies to last a few months after the cataclysm. There was no going back home for those aliens.
Listen to the video for yourself to find out more details. It would make a great mystery solving video game to discover clues and infer a timeline of events. How the game would end depends on if the player choses to use the records and preserved genetic material to bring the alien race back from extinction.
I remember listening to Art Bell on late night talk radio. Guests like Richard C. Hoagland would speculate about advanced civilizations existing millions of years ago on Mars. Maybe someday explorers will stumble upon ancient labs full of the alien technology like exotic energy sources.
Anyway, here is that Carl Sagan clip: