Seveneves new born

In the near future, an unknown force causes the Moon to shatter into seven pieces. Moon fragments will begin entering Earth's atmosphere, and blanketing the earth within two years. The story tells of the efforts to preserve human society in the wake of apocalyptic events on Earth by sending humans into space. 5,000 years later, their descendants return home to find a planet changed by time, catastrophic events, and terraforming. What could be waiting?