It's worth noting that most deep-space probes, once retrieved, will carry generally unreadable messages. Even if the instructions for reading remain intact, many such craft are made with no real intention of readability- the wear of time and space mean one could simply decide to leave a message off. But that doesn't matter, now does it? The existence of such a craft tells you enough. "We were here, we did this"- and their badly-degraded scientific instruments can tell more. Sometimes, that's enough.
