Study suggests Mercury's diameter may have decreased by up to 14.5 miles since formation
Researchers from the German Aerospace Center estimate that Mercury could have lost as much as 14.5 miles in diameter, a rate higher than earlier models predicted.
A new analysis by scientists at the German Aerospace Center’s Institute of Space Research indicates that Mercury may have contracted by up to 14.5 miles in total diameter since its formation, a reduction 10 to 30 percent greater than previous estimates. The team attributes the accelerated shrinkage to the planet’s cooling and suggests that impact-generated debris may have masked some of the surface deformation.
"More shrinking means Mercury could have a larger metal core, less light elements like silicon mixed into the metal core, or a higher starting temperature," planetary scientist Gaku Nishiyama said in a statement.
The researchers compiled existing topographic maps and found that the planet’s steep cliffs and ridges, known as scarps, display fewer visible wrinkles in the roughest regions, supporting the idea that impact material obscures some of the contraction features. The revised shrinkage rates align more closely with physics-based models of planetary cooling.
"If you can understand how fast Mercury is shrinking, you can understand how fast it’s cooling, what size it started at and what it’s made out of," planetary geoscientist Sam Birch said.
The findings come as the joint ESA-JAXA BepiColombo mission, launched in 2018, prepares to enter Mercury’s orbit later this year, offering an opportunity for direct observations of the planet’s surface and interior.