After more than 50 years, scientists have finally uncovered the moon's interior structure, showing that our closest celestial companion has a fluid outer core and a solid inner core, similar to Earth's. A team of researchers from the Côte d'Azur University and the Institute of Celestial Mechanics and Ephemeris Calculations (IMCCE) in France detailed these findings May 3 in a study published in Nature.
Astronomers have puzzled over the moon's structure since well before any probes landed there. A hot debate raged in the first half of the 20th century as to whether the moon was a "primitive" rocky world, like Mars's moons Phobos and Deimos, or whether it had a rich inner geology.
