According to our evidence, Mars had liquid water for a very long period,
I went to check this - maybe liquid water is a short-term enough thing that its mere presence is still weak evidence for an active biosphere, but apparently one timeline puts liquid water as present in large quantities for >600 million years. Bleh.
I would like to propose this as a thread for people to write in their predictions for the next year and the next decade, when practical with probabilities attached. I'll probably make some in the comments.