I didn’t know about Venus’ earth-like past, thanks!
Gemini suggests the following timeline of liquid water in the Solar System (🌊 = surface ocean):
4 bln years ago:
Earth🌊, the Moon🌊, Mars🌊, Venus🌊, Europa, Ganymede, Ceres, Enceladus, Charon
3 bln years ago:
Earth🌊, the Moon🌊, Venus🌊, Europa, Ganymede, Ceres, Enceladus
2 billion years ago:
Earth🌊, the Moon (?), Venus🌊, Europa, Ganymede, Ceres, Enceladus
1 billion years ago:
Earth🌊, the Moon (?), Europa, Ganymede, Ceres, Enceladus
Present Day:
Earth🌊, the Moon (?), Europa, Ganymede, Ceres, Enceladus, Mimas.
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Seems we are quite late to the party. 4 bln years ago there were 4 (!) celestial bodies with surface oceans, and 9 bodies with liquid water total.
Unfortunately, it’s very unlikely we find some artifact from such a distant age, unless self-repairing etc.
I generally agree, but there is possibility for small tech civs:
ancient Greeks were making mechanical computers, simple programmable machines, steam power, etc, while at populations below 10 mln, while occupying territories not much larger than the current Greece.
Very easy to miss such a civ in the geological record.