The Clouds of Saturn

The sun is a variable star. Changes in solar output have sent glaciers marching toward the equator every fifty thousand years or so. It wasn't until the first decade of the Twenty Second Century, however, that humanity realized the true extent of Sol's variability. Beginning in 2102, the sun was wracked by a series of solar flares. As such outbursts grew more frequent and violent, astronomers began to reexamine their long held beliefs about the nature of the sun.

It was with understandable horror that they realized Sol was about to enter a period of long term instability. Projections called for the sun's output to increase gradually for several hundred years. While minor on the scale of the universe, the change would render Earth uninhabitable within a century. If nothing were done to stop it, the Mother of Men would become a twin to Venus - a hothouse planet on which liquid water no longer existed.

Despite their best efforts, the scientists could find no practical method for bringing the errant star to heel. After decades of study, Earth's leaders reluctantly concluded that humankind would have to abandon its ancestral home. They began to search the Solar System for a place of refuge. The haven they chose was not one many would have guessed.