Well, Viking carried an experiment that tried to detect life. Now, the consensus is that it failed, and that the experiment was incapable of creating a useful result given the chemistry of the soil. Some people argue about that, but I am in no way qualified to take part in the debate, so I would back the consensus here.

What is odd is that there hasn't been a single other mission that's carried any experiment that has the objective of creating that result.

If the objective is to find life, why isn't anyone actually looking?

Tell me if what I've said above is in any way factually incorrect.

The Viking results were at worst, inconclusive and at best positive. And yet in both cases we have been led to believe they were negative. They are far from the only pointers to life on Mars either, since we've seen pictures of what look like fossilised stromatolites and algal mats, seasonal methane emissions, and discolorations in seasonal flows & ice.

Even the rusty coloured surface of Mars may be due, in part, to organic oxidisation processes.

We aren't talking about Richard Hoagland style cities here (although that Face on Mars is a lot less easy to explain away that some people claim).