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Message: <blockquote data-quote="John Morrow" data-source="post: 1922601" data-attributes="member: 27012">Well, Mars and Venus are pretty geographically spectacular, despite Mars being pretty dead geologically and Venus having no Moon.  And neither have much of a magnetic field, either.  Cracking due to a shrinking crust as well as asteroid impacts can give you some pretty good land masses, as can dead volcanoes, even if your core is solid.  Of course Venus rotates backward and I don't think they are sure how it's surface was formed yet.  That said, the most important byproduct of the Earth's molten core, in my opinion, is that it generates a magnetic field that protects the planet from solar radiation.  The Moon's biggest contribution to the Earth's molten core was probably the violent impact that formed the Moon in the first place, leaving most of the heavy material beind in the Earth and ejecting more of the light stuff out to become the Moon, not to mention the residual energy from the impact.FYI, two large moons are not stable.  Computer simulations to show how the Moon might have formed generated two fairly large moons about a third of the time.  When they let the simulations run, the system isn't stable.  They either run into each other or one crashes into the Earth and the other flies off into space because of how their gravity interferes with one another.</blockquote>