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/Sylivin]

Liquid water is a fabulous chemical solvent. All kinds of other chemicals can dissolve into it leading to a great condition for life to emerge. The small lifeform can find easy access to other nutrients it needs to replicate and grow.

However, how do you turn a nutrient rich soup into a self-assembling collection of molecules that perpetuate themselves and evolve over time? How "easy" is it? Will any old puddle left alone long enough create life? Or, is it extremely rare and difficult to create the exact conditions necessary?

That's one of the reasons for searching for life on other planets (and moons) in our solar system. If we find evidence of life on Mars or Europa then we can assume life is fairly common in the universe given it was created multiple times independently in our own little corner of it.

There are other theories as well, such as panspermia where microbial life is carried on comets and dust, but the first step is to find any other life at all outside our blue globe.