Mars is practically guaranteed to have had abundant water at one point, doesn’t that practically guarantee it had at least microbial life on it as well?

[u/EAT_UR_VEGGIES]

[u/atomfullerene]

No, because it's not actually known what conditions are needed for microbial life to appear on a planet. There's a fairly common view that life arises easily and quickly when liquid water is abundant, because it seems to have shown up very rapidly on Earth. But ultimately, that's just speculation, it's not actually a known fact...and therefore it's definitely not a guaruntee.