Hi, EP, Paul, List,
A problem here is that Bottke draws on this SAME
evidence to prove it's an asteroid, just as EP points to
that evidence to prove it's a comet!
The Chicxulub found fragment is carbonaceous, so
a carbonaceous asteroid is an obvious choice! But since
the difference between a "comet" and an "asteroid" seems
to be chiefly a matter of its degree of hydration along a
continuum of formation, it could mean a comet, too. (The
lack of comet samples to match the asteroid samples that
we do have makes this an argument without evidence.)
The "Nemesis" hypothesis is not Morrison's but Richard
Muller's: http://muller.lbl.gov/pages/lbl-nem.htm , published
in Nature (Davis, Hut, & Muller (v. 308, pp 715-717, 1984)).
The so-called "Nemesis" hypothesis is usually badly
misunderstood. Everybody looked at the proposed 26my
eccentric orbit and blew it off as "unstable" on the "short"
timescale of less than a billion years, which it is. Because,
sooner or later a passing star would (will? has?) perturbed
its orbit badly, altering in a major way, or setting it free of
the Sun to wander on its own. It IS unstable over the NEXT
billion years, but that's because, at solar formation, its life
expectancy was about 5.0 to 5.5 billion years. 4.5 down,
and a only little while to go...
What they missed is that THAT has become the chief
strong (rather than weak) point in Muller's theory:
http://muller.lbl.gov/papers/Lunar_impacts_Nemesis.pdf ,
where (2002) he revises his original 1984 hypothesis,
to reflect new data. And, the conclusions of his 2002
paper on impacts have since been verified by other
(non-aligned) studies. Impacts are UP lately ("lately"
meaning the last half billion years).
Here's how "Nemesis" goes now.
Imagine that the Sun has a nice little red dwarf star
companion that you'd hardly notice in a stable and
not-too-eccentric orbit for billions of years, causing no
harm, doing no damage, tossing no comets, because
it never comes close to its big brother star and its private
herd of comets.
THEN, about 0.5 to 0.8 billion years ago, a passing
star perturbs that stable not-too-eccentric orbit into the 26my
long elipse that clips through the Oort Cloud and sets loose
the comets to fall into the inner system. (There are nice
diagrams in that paper cited above, on Lunar Impacts.
I love a good diagram...)
And as long as we're arguing about the attribution of
strong but unproven hypotheses, the "rain of comets" to
the inner solar system by a big perturbation of the Oort
Cloud was first suggested by Hills in 1981, NOT by Napier
and Clube. They refined it slightly and pushed it, but it's
not their baby, well, OK, adopted...
Its chief disadvantage of "Nemesis" is that it is a totally
ad hoc hypotheses and virtually impossible to prove or
disprove, UNLESS you find the star. IF there is a "Nemesis,"
it will be found by the current "super-surveys" (like Pan Starrs
or LSST) or future even more powerful All Sky Surveys,
one of many thousand dim little stars that are loitering in the
neighborhood and trying to look harmless. Just you wait
thirty years or so...
Muller is assuming that Nemmy is a little red dwarf, but
it could also be an even smaller star, one of the newly
discovered but numerous L-Class dwarves. Their distribution
is such that, given that our star is typical, there should be
a 50-50 chance of an L dwarf within 0.75 light year, closer
than the original "Nemesis" star proposed distance. (A light
year is 63,239.7 AU, more or less. The Oort Cloud goes
out to 50,000 AU? 80,000 AU? Nobody knows...) So, an
L dwarf could be right on the edge of or even IN the Oort
Cloud! Periodically, at least.
There are at least TWO astronomers claiming evidence
for a massive object perturbing the Ort Cloud, based on
the anomalous distribution of Ort Cloud comet aphelia:
http://www.ucs.louisiana.edu/~jjm9638/matese.html
http://neo.jpl.nasa.gov/news/news071.html
The only problem is that they are each pointing to a different
patch of sky... Two perturbers are harder to swallow than
one. I'll wait for a picture of Sol b.
There is a big and delicate problem with all the "nearby
star" proposals --- it has to be big enough to make the comets
twitchy but NOT big enough to leave gravitational fingerprints
on the solar system.
This is getting long. Let's call it PART ONE.
Sterling K. Webb
------------------------------------------------------------------------
----- Original Message -----
From: "E.P. Grondine" <[EMAIL PROTECTED]>
To: <meteorite-list@meteoritecentral.com>
Sent: Thursday, September 06, 2007 10:56 AM
Subject: [meteorite-list] New KT asteroid injection theory
Hi Paul, list,
The problem with this new theory is that what hit
appears to have been a comet:
http://www.scn.org/~bh162/meteorite.html
Furthermore, the injection mechanism has been
identified as gravity perturbations due to our solar
system passing through the plane of our galaxy, which
theory agrees with 26 million year chaotically
cyclical pattern in mass extinctions:
http://www.csmate.colostate.edu/cltw/cohortpages/viney_old1/massextinctionchart.html
http://users.tpg.com.au/users/tps-seti/crater.html
The physical evidence would seem to validate Clube and
Napier's and the Italian dynamicists' work.
Morrison's "Nemisis" hypothesis and Firstone's new
hypothesis both appear to be mistaken, and it is most
likely that these gentlemen's are as well.
E.P. Grondine
Man and Impact in the Americas
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