Mars Invades Earth SpaceDaily

In the wake of the latest report on preparing for samples from Mars, the old arguments for and against have again taken center stage in this perennial debate. The basic argument against returning Mars samples is that the chances that “extant” (that is, still-living) microbes still exist on Mars are higher than NASA is making out, and that there is a genuine and serious chance that such microbes might prove harmful to Earth’s biosphere — and perhaps to human beings themselves. How accurate is this?