Overview
- The peer‑reviewed paper published Sept. 10, 2026, reports that Mercury’s cumulative contraction is 10% to 30% larger than earlier estimates, translating to roughly 19 km (about 12 miles) of additional diameter loss in the study’s central estimate.
- Researchers reached the revision by comparing global maps of visible shortening structures with a new map of surface roughness derived from MESSENGER stereophotogrammetric terrain models and inferring wrinkle features hidden beneath crater debris.
- The finding matters because the amount of radial contraction constrains models of Mercury’s thermal history and interior composition, implying a relatively larger metal core, fewer light elements in that core, or a hotter initial state.
- Authors and outside scientists caution the result is not yet definitive because MESSENGER reliably resolves features only down to several kilometers, so ESA/JAXA’s BepiColombo higher‑resolution topography and laser altimetry, starting science operations later this year, will be decisive for confirmation and refinement.
- The team notes the method could expose similar undercounts of contraction on other rocky worlds, so the approach may prompt reappraisals of shrinkage on the Moon and Mars and change how scientists read cratered, rough terrains elsewhere.