[meteorite-list] Sky & Tel. article: Mercury's Marvels

[Bernd V. Pauli]

Hello All,

Speaking of Mercury: I'm sure Pete and some others have already read
the article "Mercury's Marvels" in the April 2012 issue of Sky & Tel.,
pp.26-33.

On pp. 28-29, S&T senior contributing editor and list member J.K. Beatty
describes the three ideas (or notions) of how 'iron-hearted' Mercury formed
4.5 billions years ago.

On p. 29, you find a passage that may be a bit confusing, at least I think so:

"A third notion is that, somehow, Mercury was never Earthlike but instead
 assembled from metal-rich building blocks. Such bodies exist: metal-rich
 meteorites called CV chondrites. But what Messenger is seeing on Mercury
 isn't a good match to those meteorites' composition. An iron-poor type
 known as aubrite is a better fit (see the box on page 31)."

It's these words "metal-rich meteorites called CV chondrites" that may lead to
misunderstandings (especially among readers who are not overly familiar with
meteorites.

A closer look at Allende will show what I mean:

The Allende CV3.2 chondrite does have 23.85 % total iron but that should
not be mistaken for its FeNi content, which is a mere 0.5% according to a
post by Jeff Grossman many years ago.

Jeff wrote on Monday, 19 Apr 1999:

"In fact, Allende has almost no metal, if what you mean is metallic Fe-Ni.
 Jarosewich (1990) measured ~0.5 wt% metallic iron plus nickel in Allende.
 Most of the metal in these oxidized CV3 chondrites is the high-Ni alloy
awaruite."

Another example:

The CR2 chondrite Renazzo has 24.93 % total iron but a metal content
of only 7.4 wt%.

Cheers,

Bernd