As humanity prepares to return to the moon for the first time in over half a century, a quiet complication has emerged: we will not arrive alone. A NASA study has found that certain Earth microbes — fungi and bacteria that live on human skin, in lungs, and on equipment — could survive for weeks or months in the shadowed craters of the lunar South Pole. The discovery does not threaten astronauts so much as it threatens the integrity of the science they go to perform, raising an ancient philosophical question in a new setting: how do we know what we are truly finding, if we cannot be certain wha