to plug the finds into? It is because the Sterile Mars hypothesis (with its many variants) is the only working hypothesis that we are constantly in a bind: everything has to be fit into that box first, and if it doesn't fit, there is really nothing else to test it against, no other model.

And the Sterile Mars hypothesis is never tested itself.

If we had a working model or hypothesis that started with the premise that biology of some sort is likely or can be assumed -- as was the case prior to Mariner 4 -- then it might be possible to understand some of the more puzzling findings that keep cropping up. And yes, a biological interpretation might still be wrong; further study, however, would not be circumscribed.

There are plenty of astrobiologists around. What would be their working hypothesis for a biologically active Mars?

Cheers,