Recent research conducted by the Lunar Reconnaisance Orbiter (LRO) team indicates that moonquakes on our Moon were caused by active lunar faults -- meaning that the Moon is currently tectonically active and that the moonquakes are a result of the shrinking Moon.
Scientists believe our planet has a metallic inner core, but we can’t exactly crack it open and check. Instead, NASA is sending a mission to an asteroid named Psyche, which appears to be a nickel-iron planetary core a lot like the one at the center of the Earth.
Being a member of a science team of a planetary mission is like being a starter on a major league baseball team—you’re in the game. That’s how I felt as a member of the MESSENGER mission to Mercury. During the final months of MESSENGER’s time in orbit, before the fuel on the spacecraft was expended and crashed on Mercury’s surface, a decision had to be made—keep the spacecraft in its nominal mapping orbit as long as possible or let the spacecraft altitude drift lower to get as close to the planet as possible.