I'm guessing this could be a potentially much faster method to search the space, if there were not too many organisms up there? If you used a robot to prepare microscope slides of random soil samples, it could take an exceedingly long time to get lucky enough to find one, even if there are a lot around.

I'm not talking about detecting life. I'm talking about replicating the experiment which was performed on Mars to see if perchlorates are formed and some other reaction is responsible for the gaseous carbon isotopes.