As on the Moon, the extent of large impact cratering (i.e. craters too big to have been filled in by erosion since they were formed) serves as an age indicator for the Martian surface.
As on the Moon, the extent of large impact cratering serves as an age indicator for the Martian surface.
和在月球的一样，大型撞击陨石坑的范围之广可以显示出火星表面的年龄。
3
Because calculations and lab experiments replicating the Venusian surface and atmosphere show that emissivity decreases over time, emissivity can be an important indicator of a substance's age.