I have some very intelligent and scientifically-educated friends and extended-family members, so I thought I’d post a couple things I’ve been wondering about here.

  1. From our perspective, what would be the visible difference between a lunar surface that was the result of effervescence and one that was the result of repeated impact.  Really – look at the stain left on the counter when a soap froth has dessicated and all that’s left are the intersecting, craterous rings of the soap residue, and compare that to the surface of the moon.  I’ve tried to think of the visible differences, but the only things that I think would make sense are the ejecta from an impact crater (but there would be some splash from an effervescent crater) and the impact object itself (which often disintegrates on impact or is at least well-buried beneath the dust at the bottom of the crater).  Clearly we’ve seen the result of impact craters on earth and elsewhere enough to know that at least the majority of lunar craters come from impacts, right?
  2. Why are we so certain about the content of the inner earth? I get the iron – it’s needed for the magneto effects – but why nickel?  Why would something relegated to the 1.6% of “other” elements that comprise the earth’s crust be so plentiful in the core?   Why does water, which is so plentiful on the surface, so plentifully bound up in the minerals of the crust, not seem a likely candidate for a component of the core?  Nickel is heavier/volume than water, so why couldn’t there be both water and smaller amounts of heavier substances (copper, silver, gold?)  Why wouldn’t we think the core and mantle is as complex as the crust?  Is it really likely the earth is melted rock and metal at its center?

Does anyone know the answers to these things?