How would Mercury have a rocky mantle?

Question

From what I gather, the internal structure of most planet(s) is somewhat theoretical, but we have ways of estimating the size of the cores or the density of the mantle(s) and crust(s). (Ie, how Venus’s crust is relatively young)

Mercury however, has a rather large core – hence its comparison to a cannonball. But its mantle is apparently rocky. How would this be possible?

In: 3

Answer 1

There is speculation that Mercury at one time was a gas giant that had its atmosphere completely stripped away after 4.5 billion years of being close to the Sun. That would explain it… all that’s left is the rocky bits.