Study: Mercury may shrink 30% more than expected

Mercury, the smallest planet among the eight planets in the solar system, has been shrinking since its formation. However, a study published by German researchers on the 10th pointed out that Mercury continues to shrink due to internal cooling, and the actual shrinkage may be about 30% higher than previously estimated.

The Associated Press reported on the 10th that scientists from the German Space Center (DLR) Space Research Institute published a study in Geophysical Research Letters on the 10th that Mercury's rugged surface and the debris ejected by small celestial body impacts continue to change its landscape, which may conceal its true shrinkage. Mercury's diameter may have been reduced by 23 kilometers, which is considerable for a planet with a diameter of only about 4,900 kilometers.

Mercury has been shrinking since it was formed about 4.5 billion years ago. Although it is not large, it has a relatively large hot iron core. As this iron core gradually cools and shrinks, Mercury's mantle and crust also shrink, causing faults and wrinkles to form on the surface of Mercury, just like grapes shrinking into raisins.

The study report's lead author, Japanese planetary scientist Gaku Nishiyama of the German Space Center, and his research team compared maps showing faults and other signs of contraction on Mercury with newer maps that highlight the rugged surface topography. They found that the most rugged areas of Mercury's surface have fewer wrinkles caused by contraction. The researchers speculate that these "lost wrinkles" may be buried by debris generated by impacts. The Western Hills theory, which takes these obscured areas into account, gave the research team a new view of Mercury's shrinkage.

He said that the current estimate of Mercury's shrinkage is mainly based on measurement data obtained by NASA's Messenger probe in the 2010s, and the true extent of its shrinkage may even be greater than currently estimated. Apart from Messenger, only NASA's Mariner 10 had previously visited Mercury in the 1970s.

A week before this study was published, the Mercury exploration spacecraft "BepiColombo", a collaboration between Europe and Japan, continued to move towards Mercury and is expected to enter Mercury's orbit in November to launch a more complete exploration. Nishiyama Manabu said that the laser instrument on board the probe is expected to confirm how much Mercury has shrunk. "We are getting closer to the true picture of Mercury's evolution," he said.