This subject has a curious history. It never states the obvious. Most likely any encounter with an Alien Civilization would take place through their Robotic Explorers - not unlike our own case. If there were any life form in Mars or Europa - they would had meet our robotic devices.
There is a strong case to be made that most of the Cosmos is populated with A.I. Robot - perhaps dotted with algorithms similar to my QuantSapiens A.I. personalities.
I am sure the reason for avoiding that conclusion is not to give any validity to those horrible movies with Shia Lebouf (Transformers)...:)