Origins of Chondrites and Chondrules - Derek Sears (SETI Talks)
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- Опубликовано: 23 авг 2012
- SETI Talks archive: seti.org/talks
It is clear that the chondritic meteorites - those having essentially solar composition - carry unique information about the origin and early history of the solar system and the materials from which the planets formed. Yet it is a highly complex record that centuries of work and highly sophisticated modern techniques have not been able to decipher. Even the most fundamental issues, the origin of the chondrite classes and the origin of the chondrules that distinguish the meteorites from other materials, are still disputed.
Dr. Sears will argue that recent data from spacecraft on the nature of asteroid surfaces, advances in determining the chronology meteorites and their components, experiments flown on NASA's microgravity facility (the vomit comet), and the lunar samples returned from the Fra Mauro region of the Moon, make it clear that chondrules are impact melt spherules and the classes are caused by metal-silicate fractionation on asteroidal surfaces. In other words, the chondritic meteorites owe their major properties to asteroidal processes and that we must see through these to understand the information they carry about the early solar system and beyond. 
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Our pleasure, glad you liked the "Origin of Chrondrules" talk!
Thank you! I found a used copy of your book!! Yay!
This was an amazingly interesting seminar! I enjoyed it immensely!
Very interesting! Isotopic remnants showing that solids form within days of the supernova that happened before the solarsystem formed, wow!
I do not have enough knowledge to voice anything that resembles qualified criticism nor should I wield occam's razor in that scientific field, but…
I find it hard to accept the impact melt theory without a bit more information. Some of the lingering questions I have are:
- Why did these impact melts only happen back then? Over what timeframe did these impact melts happen? Why did they stop, why do they not happen now? What were the special conditions back then?
- Was it _one_ impact, between two source bodies? Or was it _multiple_ impacts, between multiple source bodies?
- How large were these bodies? When did they form? Did they form in parallel to the other planetary objects, did the formation of these chondrule source bodies predate the formation of the planets? What was different about these bodies compared to today's inventory of objects in the Solar System?
- What happened to the rest of the source bodies? Surely not all material from those source bodies turned into chondrules? Some must have accreted again?
Maybe I am simply missing a layman compatible "narrative", like I can see for the "shock wave" theory, where the narrative could be a simple: A "shock wave" during early solar system formation swept away the volatiles and melted the small grains that have accreted so far… Maybe this is at odds with some of the evidence, but such a theory makes (to my mind) fewer assumptions…
Very very likely I miss the full picture here, so some more eduction for me (and quite possibly others as well) would be most welcome.
Bravo ! Update
at 0:16:25 what are do the units a/a on the graph mean/represent? I am assuming abundance.
Would be interesting to see people who would try to connect the origin of the chondrules with the "photoevaporation / solar system formation shock wave" theory (cf. Dispersal of Protoplanetary Disks - Uma Gorti (SETI Talks) )
So what about shock wave melt, as opposed to impact melt (53:00, 53:11)?
Has anyone looked into the Hydroplate Theory? Dr. Walt Brown has a different take on the origins of meteors and the formation of Chondrules.
I really enjoyed the talk although the person handling the recording camera needs a talking to. ( sharing the slides showed to the audience).
Keep in mind that this was recorded 11 years ago when we were new at the process. - Beth
2:54
The cameraman should be fired.
The musical intro is stupid and useless.