Overview
- A peer-reviewed paper led by Gaku Nishiyama published Sept. 10, 2026 reports that Mercury’s long-term contraction is likely 10 to 30 percent larger than earlier estimates.
- The team reanalyzed NASA MESSENGER data by comparing maps of contraction features with maps of surface roughness and found the roughest, most cratered areas show fewer visible wrinkles.
- Researchers say debris and ejecta from impact craters can bury older contraction-related scarps and ridges, which would cause past surveys to miss a portion of the planet’s shrinkage.
- The revised estimate translates to roughly a dozen to two dozen kilometers of extra diameter loss and could change inferences about Mercury’s core size, composition, and cooling history, but the result remains provisional.
- BepiColombo’s upcoming high-resolution images and laser-altimeter topography, expected when the mission reaches orbit later this year and splits into two orbiters in November, will be the key test and could reshape models of how small rocky planets cool and evolve.