So what happens if we do discover life on Mars? Popular sentiment would quickly swing (or be swung) towards leaving Mars alone. "We've f*d up one planet, let's

So what happens if we do discover life on Mars? Popular sentiment would quickly swing (or be swung) towards leaving Mars alone. "We've f*d up one planet, let's not destroy two!", "leave Mars to the Martians", etc. Vested interests opposed to the space program would get legislation passed that declared Mars indigenous life to be a protected species, and interference with a planetary ecosystem a criminal act. That would be the end of any exploration or settlement. But if they don't include life detectors, and declare that "no life has been detected there", then discovering that they were wrong will happen once the colony is already in place. Too late, the ecosystem is already altered, might as well keep going and study it. Better to ask forgiveness than permission.