Which space agency has revealed that Mercury has a massive solid inner core?

Scientists have long been known that Mercury and the Earth have metallic cores. Like Earth, Mercury's outer core is composed of liquid metal, but there have only been hints that Mercury's innermost core is solid. Now, in a new study, scientists from NASA's Goddard Space Flight Center in Greenbelt, Maryland have found evidence that Mercury's inner core is indeed solid and that it is very nearly the same size as Earth's inner core. To explore what the core of Mercury is made of the science team used several observations from the NASA's MESSENGER (Mercury Surface, Space Environment, GEochemistry, and Ranging) mission looking at the planet's spin and gravity. The findings of Mercury's solid inner core not only help scientists better understand Mercury but also offer clues about how the solar system formed and how rocky planets change over time. The study is published in Geophysical Research Letters.