Mercury's Shrinkage May Be Far Greater Than Previously Estimated, New Study Finds

On September 10, Geophysical Research Letters published findings indicating that Mercury has decreased in size by 10 to 30 percent since its formation 4.5 billion years ago, with a reduction in width of up to 14.5 miles, surpassing previous estimates of 2.5 to 10 miles. The planet's current diameter stands at 3,032 miles. Researchers utilized data from NASA's MESSENGER mission (2011-2015) along with a digital terrain model to analyze surface roughness. Co-author Gaku Nishiyama remarked that the updated shrinkage corresponds with physics-based forecasts. Hannes Bernhardt emphasized the insights Mercury provides regarding the evolution of rocky bodies. Additionally, the BepiColombo mission by the European Space Agency and Japan Aerospace Exploration Agency is scheduled to enter Mercury's orbit later this year, commencing operations in April 2027.