I was reading an article over the weekend that the Moon has evidence of a "final" volcano on it's "far side." I am working on something that suggests the Moon would be too small to have had volcanoes, and this didn't fit with my assumption. I then reasoned that based on size, and based on the different types of cratering from impacts over time, that it would be a fair assumption to consider that the Moon is the now cooled core and is all that remains of a once thriving larger planet perhaps similar to ours. Could the Moon be the yolk of a once cracked egg type planet such as ours. Could we have had a twin? As the molten core took hits over time as it cooled, and finally perhaps one big hit causing a final volcano to erupt before final cooling of the entire mass. Has this possibility been considered? Is it realistic to assume such a scenario. Of course this assumption would suggest that a cataclysmic event occurred that caused the tectonic plates and all mass between the core and those plates to be thrown into space, only leaving the now cooled once molten core. What happened to the rest of the planet if this occurred? This is my second post on Physics Forums so I hope I am staying within the guidelines.