Study suggests Mercury's diameter may be shrinking up to 30% more than thought
Researchers say Mercury could be losing as much as 14 miles in diameter, a reduction about 30% larger than earlier estimates.
Scientists at the German Aerospace Center’s Institute of Space Research have presented evidence that Mercury’s diameter may have shrunk by as much as 14 miles, a figure about 30% greater than earlier models suggested. By juxtaposing older fault-line maps with recent assessments of surface roughness, the team found that the planet’s roughest regions show fewer visible contraction wrinkles, likely because impact debris masks them.
This revised estimate relies on data from NASA’s Messenger spacecraft and will be further examined by BepiColombo’s laser instrument when the joint European-Japanese probe enters Mercury’s orbit in November. Lead researcher Gaku Nishiyama, who also works at Hokkaido University, says the study sheds new light on how Mercury’s oversized iron core cools and contracts over billions of years. The findings could also inform models of other bodies undergoing similar internal cooling and surface shrinkage. Only two spacecraft have visited Mercury before—NASA’s Mariner 10 in the 1970s and Messenger in the 2010s—making these new insights especially valuable.
