2. Messages
This is the most attractive possible artifact type to find,
as it shows that not only does alien intelligence exist, but
that it cares (or cared) about communicating with other
intelligent beings, and may even be willing to impart
knowledge and wisdom to us. A message would likely be
placed where it could be easily located, and might also
have some sort of beacon attached, so that orbital instruments
would be able to find it even if the message capsule
was buried. However, the details of these features can
vary widely depending on when the putative aliens visited, and how long they expected the message to need
to last.