[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Carbonates and CI Chondrites
Hello again Frank,
This is all so fascinating to me that I'm shirking my usual evening duties
to plow through old books and papers. Thank you so much for answering my
earlier questions.
I assume that since the fall of the Murchison, fewer people have explored
the organics of Orgueil. Therefore I've had to delve deeper in the
literature to find material on the Orgueil regarding its organics. I
apologize for the age of the cited literature (some is older than me).
Mason (1962) writes "Calvin (1961) has studied the infra-red and
ultra-violet absorption spectra of extracts from the Murray and Orgueil
carbonaceous chondrites. He concludes that these extracts contain a wide
variety of organic compounds, including hydrocarbons and heterocyclic
bases. He found no amino acids in aqueous extracts either of Murray or
Orgueil."
Norton (RFS, 1994) does highlight some about the organics in Orgueil, but
later in the paragraph, dismisses them as terrestrial contamination
(pp196). McSween (Meteorites and Their Parent Planets, 1989) also notes
certain complex organics in Orgueil as "an elaborate hoax (pp62)."
Therefore, I can't answer if the organics in Orgueil are in the form of
amino acids or not. As I looked through some of the early research, it
seems apparent that many of the questions currently being asked will
ultimately lead back to a question of which there were heated debates about
in the early sixties. Namely, how did chondrules form. If that piece of
information was in place, the contradiction of the most primitive type of
chondrite having no chondrules should easily be answered. Then answers to
questions such as why there is a fairly distinct line between carbonaceous
chondrites and ordinary chondrites could be explored better.
Just guessing, but from the heat generated by arguments (for example
between Urey and Goles et al.) that maybe some issues were just accepted as
unresolved, and the other research directions continued in the absence of
critical information.
McSween also highlights that "Considering the degree of alteration that C1
chondrites have experienced, it is surprising that their compositions still
match that of the sun so closely. This alteration must have occurred
without significant chemical exchange with the surroundings (pp54)." He
then points out that a type 3 chondrite is nearly unaltered with the
higher petrologic types (4, 5, 6, 7) indicating a greater thermal
metamorphism, and lower grades (2 and 1) indicating a greater aqueous
metamorphism.
I have heard of the similarity of carbonaceous chondrites, namely Orgueil
and Allende, to the composition of our sun. In your excellent posting, you
even note: "By measuring the elemental abundance in the Sun, and compare
it with CI chondrites, they plot very near one another." However when I
lookup the Sun's composition, Kaufmann (1988), lists it as (by weight) 75%
Hydrogen, 24% Helium, and 1% all other elements, but has a density of
1.41g/cm^3. What is the relationship (or how can a relationship exist)
between carbonaceous chondrites to the sun, and to asteroids, and to other
chondrites including E's and ordinary ones if they themselves are not
specifically all related in the same way?
Most sincerely,
Martin
Follow-Ups:
References: