[meteorite-list] Fw: Origin of chondrules

From: MEM <mstreman53_at_meteoritecentral.com>
Date: Wed, 13 Mar 2013 23:06:40 -0700 (PDT)
Message-ID: <1363241200.48858.YahooMailNeo_at_web142406.mail.bf1.yahoo.com>

Didn't see this post make it out of the hopper so resending:
A couple points as I haven't read the paper...

There is a good explanation as to the origin of CAIs stemming from a bi-polar venting phase in the T-Tauri phase of out proto-sun right before it kicked off full fusion output.? During this extended event, refractory materials( aka CAI's) were released in high speed jets from each pole. The CAIs slowly folded back into the proto-solar disk, concentrated in a ring at several AUs from the sun. This scenario also would account for the apparent concentration of CAIs beyond Neptune or where ever it is that Carbonaceous Chondrites form.?


As to chondrues, they should be younger than CAIs if the above is valid and of course they are. I believe chondrules come from multiple sources. One of which includes mineral grains with multiple quick trips in and out of hot locales followed by trips through chilling ones. I've seen olivine chondrules with multiple relic initial crystalization frameworks within the chondrule suggesting partial melting followed by rapid chilling before complete crystalization. ? I think typical irregular Carbonaceous chondrules stem from mineral grains which owing to their formation much further away from these hot and cold gas zones don't get as rounded as those we find in typical Common Chondrites.


A planetesimal, by definition, represents a body already differentiated
into mineralogical layers. Splash /spray wouldn't seem to account for the
co-mingling of the different types of chondrules we find in real life.?
It has always been our understanding that it takes chondrules to
coalesce into planetesimals not the other way around.

As to the extremely slow collision speeds, I haven't done the math, but I can't readily accept such slow speeds of collision (1-100 m/s) between planetesimals multiple tens of miles in diameter. Merging bodies of that size should have velocities of at least 1k/s and perhaps up to 3(?) k/s just from minimum mutual acceleration toward each other(Note: one bizzare scenario does come to mind which has them tidally locked and skimming each other before they totally disintergrate and form a unified body).? Also,


Elton
Received on Thu 14 Mar 2013 02:06:40 AM PDT