Study suggests Mercury's diameter may be shrinking up to 30% more than previously thought
Researchers from the German Aerospace Center say Mercury could have lost as much as 14 miles in diameter, a rate about 30% higher than earlier estimates, and the BepiColombo mission will test the findings.
Scientists at the German Aerospace Center’s Institute of Space Research reported Thursday that Mercury’s overall shrinkage may be about 30% greater than earlier calculations, implying a loss of up to 14 miles (23 kilometers) in the planet’s diameter. The planet, which measures roughly 3,000 miles (4,900 kilometers) across, has been gradually contracting as its oversized iron core cools and contracts over billions of years.
The team arrived at the new estimate by comparing fault maps that record contraction-related wrinkles with newer maps that highlight surface roughness. They found that the roughest regions showed fewer visible wrinkles, suggesting that impact debris may be covering some of the contraction features. After adjusting for these obscured areas, the researchers concluded that Mercury’s shrinkage has been underestimated.
"We are quite excited," said Gaku Nishiyama, the study’s lead author and a participant in the BepiColombo mission, adding that the work brings scientists closer to understanding Mercury’s evolutionary history.
The findings appear in the journal Geophysical Research Letters and come as the joint European-Japanese BepiColombo spacecraft prepares to enter Mercury’s orbit in November. Its onboard laser instrument is expected to provide direct measurements of the planet’s current size and verify the degree of contraction inferred from the new analysis.