Mercury, which is about one-third the size of Earth, may have shrunk more in its evolution than scientists originally thought.
A new study suggests that the tiny planet may have contracted 10% to 30% more than previous models suggested — meaning the planet’s total diameter shrunk almost 12 miles (19 km) since Mercury was formed. (Mercury’s diameter today is roughly 3,032 miles (4,880 km).
Previous missions overlooked the extent of the shrinkage because impact-crater debris on Mercury's surface hid the evidence, according to a study published Thursday (Sept. 10) in the journal Geophysical Research Letters. That size difference is important when researchers consider the planet's history, said Gaku Nishiyama, a planetary scientist at the German Aerospace Center Institute of Space Research and an author of the study.
"Because Mercury's evolution is driven by its cooling, the amount of contraction — an indicator of the extent of cooling —...
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