[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: P/Tr impact?
Some stuff deleted, but still long.
Jeff Hecht wrote:
> >...Holtz, Jr. wrote:
> >Some thoughts ...:
> > In any case: no reason to suspect that the body that brought these
> >fullerenes to Earth was anything other than an ordinary chunk of our own
> >system. (Holtz)
> Both comets and asteroids are possible; we know very little about
> asteroid composition. Another possibility raised earlier is a nearby
> supernova. What the isotopic ratios seem to indicate is that the
> buckyballs formed near a star in a region of high pressure. That
> material could have been processed through the solar system or
> arrived directly. (Hecht)
Jeff and Tom, I'm speaking from memory, so may well be wrong. I had the
impression that the isotope ratios were typical of the enviroment of a more
carbon rich star than ours, so would have had an extrasolar origin. Of course,
with the exception of hydrogen and some of the lighter elements, every atom on
earth was originally processed or created in some other star and further
processed by one or more supernovae before it wound up here. But the ratios (if
memory serves) would imply that the buckyball itself was formed in the environs
of the other star. And that would statistically imply the likelyhood of
relatively high velocity at the time of earth impact. So compared to the K/T
there's a possibility that we would receive more kinetic energy from a smaller
impactor. The massive African(?) sediments that appear to have been a
consequence of the P/T transition might be a place to look for possible
redeposited extrasolar materials.
> The only thing known about their age is that they
> have been on Earth since the Permo-Triassic boundary.
> >But are these fullerenes really there, or really ancient? .....
> These are interesting questions.
> >, other more
> >mundane sources can produce fullerenes: forest fires, for example, or mass
> >spectrometers (i.e., the tool used to find and separate them can apparently
> >generate them as well... URK!).
> These sources would have had terrestrial isotopic ratios for helium
> and argon. If Becker's results are correct, the buckyballs from the
> P-Tr do not.
And electric arcs, and the chimneys of domestic oil lamps -- but they too would
have domestic isotope ratios.
> >, there is the very real possibility that a
> >P/Tr impactor would have struck oceanic crust .... might be less likely to
> >shocked quartz>....., given the mafic composition of
> >oceans (as opposed to granitic continental material)....
> Iridium, shocked quartz, and spherules --.......the rocks don't look
> similar.... seem to indicate that whatever
> happened at the Permo-Triassic boundary was both qualitatively and
> quantitatively different than at the KT. A comet impact in the deep
> sea might meet those criteria, but so could other events.
For example, a smaller impactor coming in at a much higher velocity. There have
even been suggestions of dark matter, but that might be pushing the probability
envelope a bit.
> Why were extinction rates higher for marine fauna than
> terrestrial vertebrates?
> This is an interesting paper, but I don't think it has "the" answer.
Good question, and me neither.