I took the title of this panel to mean how could explorers from earth determine what happened to an extinct alien race based on the clues they left behind on their home planet. In order to make this question manageable (and more interesting), I assumed that we are talking about a technological society similar to or more advanced than our current society at the time of its extinct. This assumption lead naturally to the question, "how could we be destroyed (or destroy ourselves) and what evidence would this destruction leave behind?"
| Cause of Extinction | Residual Evidence |
| Star Trouble - Red giant, nova, etc. | Obvious upon entering the star system. |
| Impact - Large comet or asteroid | Look for impact crater or layer of extraplanetary material. |
| Natural Disease | This one might not leave many clues. Look for "written" records left by the victims. |
| Natural Global Climate Change | Examine the current atmospheric composition and the geologic record. Possibly use global atmospheric models. |
| Alien Invasion | See Global War items below plus evidence of alien habitation. This one could be bad news for the Earthers. |
| Cause of Extinction | Residual Evidence |
| Global War - Explosive Weapons | Look for bomb craters and "selective" destruction. |
| Global War - Biological Weapons | Same as for Natural Disease above. |
| Global War - Chemical Weapons | Look for traces of the chemical, but there might not be any if more than a few hundred earth years has past since the release. Look for "written" records left by the victims. |
| Accidental Biological Agent | Same as for Natural Disease above. |
| Exhaustion of Natural Resources | Look for "missing" natural resources. |
| Accidental Global Climate Change | See Natural Global Climate Change above. |
| Breakdown of Social Order | This might be a good explanation if no other causes for the extinction could be found. Also look for "written" records left by the victims. |
| Accidental Chemical Agent | Same as for Global War - Chemical Weapons above. |
| Died of Boredom | See Breakdown of Social Order above. |