Earth, Gold, the Early Solar System, and New Ideas

"Ancient Crashes Blasted Precious Metals Into Earth, Moon and Mars"
Mike Wall, Space.com (December 9, 2010)

"Gigantic collisions on Earth, the moon and Mars 4.5 billion years ago injected precious elements such as gold and platinum into the developing worlds, a new study suggests.

"In the last days of planet formation, a body as big as Pluto likely slammed into Earth after the planet had been clobbered by a Mars-size object, researchers said. Mars and the moon absorbed smaller but still devastating blows, they added.

"These traumatic cosmic crashes may have knocked Earth off its axis by 10 degrees. But they also delivered gold and other elements into the bodies' upper reaches, and possibly brought huge amounts of water to the moon, researchers said...."

The point at issue is that there's quite a lot of Gold, platinum, palladium, and other elements at and near Earth's surface.

Which shouldn't be there. Assuming that current models for how planets formed are fairly close to being accurate.

The models could be wrong - but there's a whole lot of other data that supports them.

The Space.com article runs through a newish explanation for why thar's gold in that there crust on Earth - which is involved with an explanation for the size range of asteroids is skewed toward big bits of stuff. And the Borealis Basin on Mars. Assuming that it's an impact feature. Which isn't certain.

That lack of certainty will probably be the norm for a while, particularly since we're starting to get data about other planetary systems.

"...The study paints a violent picture of the solar system's early days, with the inner planets being walloped heartily shortly after their birth. Such pummelings might be common in other newly forming solar systems, according to Bottke.

" 'Because we can reproduce some of these things in our models, I think that probably means we're fairly typical,' he said. 'But that's just a guess.'

"If our solar system is atypical — if young planets in other solar systems were spared pummelings by massive impactors late in the formation process — then alien planets might be different in significant ways, Bottke said. Their mantles, for example, might be lacking in siderophiles like gold and platinum, which we value for a variety of reasons.

"In any event, Bottke said he hopes the study serves as a conversation starter, getting scientists thinking about the planet-formation process in a more general sense...."

The way that the new models match what we can observe in the Solar system is exciting - and so is the uncertainty reflected in "that's just a guess." There's a lot yet to be learned - and now scientists have a new set of questions to ask.

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