Overview
- A peer‑reviewed paper published Sept. 10, 2026 reports that Mercury’s long‑term radial contraction has been underestimated by about 10% to 30%, based on reanalysis of existing spacecraft data.
- The team used stereophotogrammetric digital terrain models from NASA’s MESSENGER images and a global surface‑roughness map to show that crater ejecta and rugged terrain mask shortening structures such as scarps and ridges.
- Accounting for those hidden features raises the estimated loss in Mercury’s diameter by roughly 12 miles (about 19 kilometers) in many summaries and by up to about 14 miles (≈23 km) in some calculations.
- Greater shrinkage implies a different interior: a relatively larger metal core, fewer light elements like silicon or sulfur in that core, or a hotter initial state that would drive more cooling and volume loss.
- The result relies on MESSENGER’s spatial limits and is expected to be tested and refined by higher‑resolution topography and laser altimetry from the ESA/JAXA BepiColombo mission when it begins comprehensive science mapping in late 2026 and 2027.