Two SF ideas that certainly have been made to a novel at least twice - but I do not know them

a) The two really different civilizations that find each other at a distance that is conquerable: Say we found that Mars indeed has living "people" on it. When, and how, would we have found out? When Lipperhey invented the telescope, and Galileo looked at Mars? Probably it would have taken a few more years - and it is interesting whether we would have seen them first, or whether we would have shot some probe at them, unsuspecting. And how about the converse? A probe lands nicely on the Earth ...

b) Statistically, we would not meet: One of us would be dead for probably billions of years when the other one came around. What happens?--in detail, I mean. There are many SF novels where people stumble on other planets with crumbling pillars. But we will never go to other planets--we will only send probes. So what happens when that first Russian probe crashes onto Mars and, during its fall, makes a few pictures of something which looks too controlled to be "nature"? Or would that happen--would a probe that falls on Earth see anything human? Even if that happens by chance, would the second probe see houses, roads, or at least a few rectangular fields? How would those at the other end of the probe think, react, continue?

If someone knows of intelligent novels dealing with such topics, drop me a note! (if you happen to send a probe to this blog, of course--which I do not at all promote, so this might be a sort of self-referential experiment, wouldn't it?)