Mercury’s rotation rate oscillates with a greater amplitude than it would if the planet’s core were entirely solid. That is the conclusion of a team of researchers, comprising Jean-Luc Margot from Cornell University; Stan Peale from the University of California, Santa Barbara; Raymond Jurgens and Martin Slade from the Jet Propulsion Laboratory in Pasadena, California; and Igor Holin from the Space Research Institute in Moscow. They base their finding on recent radar measurements and the decades-old data from the Mariner 10 probe. 1
Mercury’s structure is similar to Earth’s: It contains a dense metallic core surrounded by a silicate mantle and a rocky crust. But seismic measurements provide additional information about Earth that’s harder to come by in the case of other planets. It’s known that the outer part of Earth’s core is molten, due mostly to the heat produced by radioactive decay, whereas the inner core is kept solid...
