Mars

Mars had life until the last decades of the 1890s. Of course, we hadn't had contact with them since the Mythic Age, but astronomers, cosmographers and seers in the 1700s and 1800s did note the canals and even a few of their major cities.

By the 1910s the entire planet had become a cold, dead planet. Its cities fallen to ruin, its canals dried and desiccated, its atmosphere stripped away by the solar winds. Whatever killed the red planet did such a complete job that by the time we sent our first missions to Mars, there were only a few scattered remnants of the civilizations that once flourished there--the Face being the most notable one--and even those were crumbling to ruin.

The fate of Mars is one of the greatest mysteries of the modern age, and information about it is kept tightly under wraps by Majestic-12 and their agents in NASA. They want to figure out how to stop whatever happened to Mars from repeating here on Earth--hopefully without alerting mankind to just how tenuous their lives here on this planet truly are.