The collapse of the first base on Mars was a harrowing one, sparked by a software error leading to the collapse of the oxygen futures market. Internal security measures nobody would later admit to having known about led to a drastic fall in labor supply, and attempts to uphold the base anti-union bylaws spiraled into older forms of violence. The last survivor, a former bodyguard of one of the founders, died while trying to use her employer's untested emergency — and, it turned out, overhyped — cryogenic pod, but the life support systems had become irrecoverable long before.
A century later, when Earth's partial eco-technical reconstruction by the billions left behind made colonization viable again, none of the new bases was set up near the bolthole, and it was coded into the teaching intelligences not to tell the children they were bonded to about the place. Even 22nd century children would think the ruins haunted enough to want to explore them, and even 22nd century grownups agreed with them enough to prefer them not to.