Fact #144
Missions
China brought back lava from a plain that turned out to be two billion years old — a billion years younger than anything Apollo returned, and younger than the crater counts predicted.
Dating surfaces by counting craters relies on samples with known ages to calibrate the count. Before 2020 the calibration had a two-billion-year gap in the middle of it. Chang'e 5 landed a sample right in that gap, which quietly adjusted the estimated age of a great many surfaces on Mars and Mercury as well.
Source: Li et al., Nature 600, 54 (2021) · checked Sep 2026