Science, gold and ducks

It’s kind of surprising that there is still a far amount of uncertainty about the formation of planet Earth.  I didn’t realise this, for example:

The planets formed when tiny rocks collided, forming ever larger lumps. Then, after Earth was born a second planet about the size of Mars crashed into it. This cataclysmic shock blasted a huge cloud of material into orbit, where it coalesced to form the moon.

This neatly explains the moon, but poses a problem. The collision re-melted the solidifying Earth, allowing heavy materials like iron to sink into the core. But some elements, called siderophiles, dissolve in molten iron, including gold, platinum and palladium.

"We shouldn't have any siderophiles in the crust or mantle," says William Bottke of the Southwest Research Institute in Boulder, Colorado. "But actually we see them in surprising abundance."

The obvious solution is that they arrived after Earth cooled. If so then the moon should have siderophiles too, and it doesn't. Rock samples show that it has 1200 times fewer than Earth.

The article notes that the idea is that the earth was hit by a few, really big, gold bearing planetoid things, but they missed the moon on the way in.

This is a pity.  Having an gold bearing region on the Moon might make have made space exploration take a different path.

And, come to think of it, this reminds me of the classic Carl Barks Uncle Scrooge comic “The 24 Carat Moon” which I read as a child.  No doubt this was why I wanted to post about this, before I even remembered the comic.