Mercury shrinking up to 30% more than expected

Researchers have discovered that the planet Mercury is shrinking up to 30% more than previously estimated. An international team of scientists, led by Gaku Nishiyama of the German Aerospace Center (DLR) Institute of Space Research, published their findings in the journal Geophysical Research Letters.

The planet’s contraction is evidenced by wrinkles and steep cliffs known as scarps on its surface. Scientists believe the process is caused by the planet cooling over billions of years, a phenomenon compared to a balloon losing heat. The study suggests that impact craters and debris may have previously obscured the true extent of this shriveling.

This accelerated shrinking provides new insights into Mercury’s internal composition. According to Nishiyama, the increased contraction suggests the planet may possess a larger metal core, a higher initial temperature, or fewer light elements like silicon mixed into its core. Understanding the rate of cooling helps scientists reconstruct the planet's evolutionary history.