[meteorite-list] Vesta heating

From: Jamie Stephens <J.Stephens_at_meteoritecentral.com>
Date: Thu Apr 22 09:53:38 2004
Message-ID: <3E1066D3.14C6C946_at_morphism.com>

List Members,

I got myself a small slice of NWA 1109, and I thought it was about
time that I learned something about 4 Vesta (and the various alleged
Vestoids). The basalt is interesting. (I'm proud to write "basalt";
I only recently learned what that word means. Duh.)

As far as I can tell, it looks like 26Al decay is the arguable
consensus for the source of Vesta's primary magma-forming heat. Yes?
Maybe there are still some questions: the relative lack of 26Mg in
eucrites; the uncooked Ceres. Anyway, I think I read that 26Al is
exclusively a supernova product. If so, when did it arrive in the
nebula? If not, when and where did it originate?

Warning: I have almost no idea what I'm talking about.

26Al has a relatively short half-life (730,000 years?), and I'm
guessing that Vesta needed a relatively large amount to cook. (How
much?) Folks have suggested that a supernova triggered condensation,
right? Maybe this supernova contributed the 26Al coincidentally just
before main belt condensation, but that sequence would be unlikely --
I guess.

  t_1: Some supernova blasts nebula with X g of 26Al
  t_2: 4 Vesta mostly (?) forms.
  t_3: 4 Vesta starts to cool. Old eucrites form.
       Somewhere in 4.510-4.55 billion years ago?
  t_4: 4 Vesta is cool. Cumulate eucrites form.
       Somewhere around 4.445 billion years ago?

Questions: Am I in the ballpark? What's the latest word on Vesta
heating? And does that story support a condensation-catalyzing
supernova? Would it be possible to identify the supernova remnant?
Or did the 26Al originate in some other way?

Some references (not fully digested by me):

  Meteorites and Their Parent Bodies, McSween
  http://www.lpi.usra.edu/books/AsteroidsIII/pdf/3034.pdf
  http://www.lpi.usra.edu/meetings/lpsc97/pdf/1308.PDF
 
http://ijolite.geology.uiuc.edu/colloquium/Discussion%20Papers/wadhwa_paper.pdf

Thanks in advance for any news or corrections.

--Jamie Stephens
Received on Mon 30 Dec 2002 10:31:31 AM PST