The Moon, the Earth, and Doughnuts

I really love thinking about space. Often times these mental meanderings lead to fun questions for which scientists can conveniently provide answers. This morning I was reading about a deep hole found in the moon. Apparently it may have formed from a collapsed lava tube. I’d never really thought about it but I guess it makes sense that the moon had lava. It’s such a gray passive little neighbor that it hadn’t ever really come to my mind.

Not surprisingly, it’s believed that the moon’s core has cooled so that the hot center isn’t so hot any more. It’s a lot cooler than the Earth because it’s surface area to volume ratio is higher, AND Earth has the convenience of some radioactive decay going on downstairs which is keeping things toasty. There’s a great article about it here.

Apparently our inner core is about 4,000 to 6,000° C (hot° F). For some reason I always thought our core was so hot that it was pure liquid lava… but it’s not. The pressure is high enough to keep the Iron and Nickle solid (Iron under 1atm melts at about 1,500° C). Outside of the core there’s some liquid iron and then the mantle. All this time I thought the mantle was a torrential river of burning, but it actually moves really slowly. “Average circulation of 4cm per year.”* 4cm per year? weak.

Anyway, all this leads me to the thought that the Earth is less like a Jelly Munchkin with its delicious powdery shell and mouth-watering gelatinous insides delightfully bubbling up at key sugary volcanic locations and more like an unripe peach with a skin, flesh, and solid pit. How disappointing.

A few sources
another source
a third source

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