Why does the lack of craters on Sputnik Planitia suggest geologic activity on Pluto?

The absence of impact craters on Sputnik Planitia indicates that the region is a very young surface feature. In planetary science, a lack of craters suggests that a surface has been recently resurfaced or modified by geologic processes, which effectively erase or cover over older impact marks.12

Because the solar system is filled with debris that creates craters over time, a smooth, crater-free area like Sputnik Planitia implies that active geologic mechanisms—such as volcanic or tectonic activity—have been at work to refresh the landscape. This observation serves as strong evidence that Pluto is not a geologically dead world but remains active, with processes capable of altering its surface appearance.12