E.P. Grondine
Man and Impact in the Americas
as alway, contact me off list for the list members
special
--- Greg Redfern <[EMAIL PROTECTED]> wrote:
Sterling,
As always, nice write up. Looking forward to part
2.
I would like our colleagues to consider the
Murchison fall as a
meteorite that could very well be the missing link
between an "active"
and "dead" comet. With its' high % of water (13%) by
volume and the
scores of amino acids it contains - I'm sure Bernd
could give us the
exact water % and AA count to date and which I
believe is 98 - Murchison
is quite extraordinary.
Each of the NASA and ESA missions to comets and
asteroids are helping
us to fill in the gaps of our knowledge. But one has
to wonder what is
left when a comet has sublimated all of its'
volatiles into space?
Nothing but a meteoroid stream? Or is there a
central solid body or
rubble pile that acted as a gravitational anchor to
collect and hold all
of the comet's original volatile material?
Maybe the analysis of the STARDUST comet material
will help us gain
some knowledge. I for one INTUITIVELY believe that
an asteroid can be a
dead comet as it is a logical end state following
countless orbits
around the Sun.
All the best,
Greg Redfern
NASA JPL Solar System Ambassador
http://www2.jpl.nasa.gov/ambassador/index.html
WHAT'S UP?: THE SPACE PLACE
http://www.wtopnews.com/?sid=600113&nid=421
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]
On Behalf Of
Sterling K. Webb
Sent: Thursday, September 06, 2007 5:21 PM
To: E.P. Grondine;
[email protected]
Subject: Re: [meteorite-list] New KT asteroid
injection theory PART ONE
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: <[email protected]>
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/massextincti
onchart.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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