Mercury appears to have shrunk more than scientists previously thought, with a new study estimating that its diameter has decreased by as much as 23 kilometres. The new estimate is around 30% higher than previous calculations.
Mercury, the smallest planet in the Solar System and the closest to the Sun, has a diameter of around 4,900 kilometres. It has been gradually shrinking since it formed about 4.5 billion years ago, as its interior loses heat.
The planet has an unusually large iron core relative to its overall size. As the core cools, it contracts, pulling the mantle and crust with it. The surface is then forced to adjust to a smaller internal volume, creating large faults and folds — geological structures that resemble “wrinkles” on the planet’s surface.
Mercury is the smallest planet in the Solar System, with a diameter of around 4,900 km, and the closest to the Sun.
Researchers believe that not all of these “wrinkles” had previously been properly accounted for. In some areas, material ejected by impacts and crater formation may have covered older signs of contraction. When scientists included these rougher areas in their calculations, they arrived at a higher estimate of how much Mercury has shrunk overall.
The study was based on data from NASA’s Messenger spacecraft. The next major test of the findings is expected to come from the European-Japanese BepiColombo mission, which will be able to measure the planet’s surface features and evolution more accurately.
Source: Associated Press
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