Best evidence yet of aqueous Mars

There's a bunch of accompanying (non-Open Access) paper in this week's Science. I still have my doubts: whoopee for evidence of surface running water and gosh for the aberrant methane but all this is circumstantial at best. I still feel burned about ALH84001 (NASA's Mars Meteorites page; BBC story on the debate over nano-/nannobacteria). We have no real idea of the necessary and sufficient conditions for life because our sample size is one. Liquid water near the surface of a planet a suitable and stable distance from a well-behaved star might be a necessary condition for life, or merely a sufficient one. There might be many more necessary conditions. I don't put much store in the Drake Equation for the same reason. There will be Life out there but it is also true to say that we are alone.