Earth That Is

In the first half of the 21st Century, the sun became unpredictable in its output. Rather than following the usual cycles and rhythms, it became more extreme. Some years were much colder, while others were much hotter. This led to severe disruptions of the climate and the biosphere, which in turn led to starvation and bloody resource wars in the 2020's and 2030's. Between the increasing heat, the ecological collapse, and the pollution from nuclear warfare, Earth slowly lost its ability to support human life. Many scientists suspected that the sun itself would expand or explode, destroying the Earth outright. By the 2050’s, evacuation was accepted as humanity’s only choice for survival, and the GEA seized control of the solar system. Early attempts to terraform the moon, Venus, and Mars were abandoned, due to fears that the sun would simply make them uninhabitable in time. The sun grew steadily hotter, and it was discovered that Earth would be completely outside the habitable zone by 2120. The Great Migration was underway by the 2090’s, and the solar system was officially abandoned by 2102. That's the official story, as taught to students of history in the 'Verse. The truth is more complex.

Humanity had not completely abandoned its original home, however - numbers of diehard colonists remained on Mars, continuing the terraforming work they had started. In the asteroid belt, on Pallas, and Ceres, and Vesta, human settlements thrived. In the asteroids near Jupiter, stubbornly independent miners and settlers eked out a marginal living amid the millions of tumbling rocks, unconnected to the bulk of humanity. These few survivors watched as the vast exodus of Arks receded into the interstellar void. Several Arks, along with their populations and valuable terraforming equipment, suffered damage along the way, and limped back to the solar system in the 2160’s. Menaced by the fiercely independent (and increasingly alien) Belters, the Arks took shelter near Jupiter. By 2180, the Sun had settled into a stable pattern - though burning hotter than it ever had in the past, it at least remained as it was. Earth was now on the ragged hot edge of the habitable zone, while Mars was now warm enough to support human life largely unprotected.

Three centuries after the end of the world, humanity was doing fine in the home system.