Mercury is shrinking faster than previously estimated

A new study published in Geophysical Research Letters reveals that Mercury is shrinking significantly faster than previously estimated. Researchers found that the planet's contraction rate may be 30% higher than prior models suggested, resulting in a diameter reduction of approximately 19 to 23 kilometers (roughly 12 to 14 miles).

Led by Gaku Nishiyama of the German Aerospace Center (DLR), the research utilized data from NASA's MESSENGER mission. Scientists determined that previous estimates underestimated the shrinkage because impact craters and debris from asteroid bombardments have historically obscured the planet's tectonic 'wrinkles' or shortening structures.

This contraction is driven by the cooling of Mercury's interior over 4.5 billion years. As the core cools, the planet's volume decreases, causing the crust to buckle and form ridges. The European-Japanese BepiColombo spacecraft, which recently separated from its cruise stage, is expected to provide further high-resolution data and laser measurements to confirm these findings as it approaches Mercury's orbit in late 2025.