Scientific observations confirm that Mercury, the closest planet to the Sun, is continually shrinking as its iron-rich core cools over time.
Because Mercury’s core was extremely hot during its formation, the gradual loss of internal heat over billions of years causes its metallic interior to contract. This internal contraction places tremendous pressure on the planet’s outer crust, resulting in massive surface faults, cliffs, and distinctive rocky ridges.
Estimates indicate that Mercury’s radius has decreased by several kilometers since its early history. While this contraction occurs far too slowly to be observed on a human timescale, scientists note that Mercury is not merely a static or biologically dead rock. The ongoing thermal evolution and residual heat within its core demonstrate that active geological transformations continue beneath its surface today.
