Comet Enthusiast

Wow! Let me say that again: wow! That is quite possible the most poignant and beautiful picture I've seen! (I.e., in the last months, seeing as how our minds work. )

It was also quite easy to understand the illustrated bounce back symmetry inside the earlier ejecta from the text and the reference. (Its fig 1, especially the more symmetric right column.) Thank you, Steve!

People here have hashed out nucleosynthesis to everyone's satisfaction I think. A datum I seem to remember is that big bang (BB) nucleosynthesis lithium used to be considered deficit in old (pop I ?) stars by a factor 2 or so, but IIRC newer models shows how it has preferentially settled "out of sight" spectroscopically and tested yet again standard cosmology predictions.

So what can I do but continue to wax poetically. As we all know, our solar system shows signs to have been birthed by a cloud that was compressed, or at least seeded, by a supernova, leaving its telltale marks of relatively high metallicity.

This has, AFAIU, been a little question mark as far as planetary formation goes, too little metallicity and presumably fewer planets, too much metallicity and other barriers for planet formation. It is a fun exercise to peruse an exoplanet database, ask for planets by star metallicity, and see that the Sun even so places among the maximum in the distribution of "planet producing stars".

This is a marginal toe in to last weeks falling-on-my-but-in-perplexity press release. Researchers have found Earth material that are as old as Earth itself!

Alas not crust, but mantle material, which reservoir dates back to a few tens of millions of year after Earth formation. It has been punctuated and dragged to the surface on Baffin Island by those mysterious deep hotspots. Here it is Iceland's hotspot that used to reside there 60 Ma.

The reservoir mantle material is dated 4.55 – 4.45 Ga, Earth at 4.55 Ga. But the accompanying model shows that its composition is explained by a rapid quench of a Earth crust over 30 My, coinciding with Earth differentiation and core formation.

This iron rich material was then too heavy, broke up and sunk, leaving the mantle composition to be the Baffin island one.

There are many consequences drawn from this single and, to me, unexpected discovery. Among others, the models of Earth/Moon as primordially chondrite material is shored up in the original paper, as well as models for early core formation even in small bodies. I believe, but its iffy to say for a layman, that the Earth/Moon impactor vapor homogenization model is also shored up, explaining the exact O and W ratio match between Earth and Moon.

But, bother! If we can find mantle material from up to the initial Earth formation, why is the crust history "broken" the earliest 0.7 Gy? (Oldest found crust is 3.8 Ga. Some zircon crystals are 4.4 Ga though.)

Now Carlson holds out the alluring possibility that the first crust is still to find in reservoirs, but in molten form explaining seismological observations. Maybe so, but that is a long stretch. And even molten, I'll take that morsel, but we can't get to it! Where is a hotspot when you need it?