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(meteorobs) Excerpts from "CCNet 60/2001 - 26 April 2001"




An (off-topic for 'meteorobs') contribution from our own Marco Langbroek,
in the on-going debate about cosmic impacts and human evolution. It's good
to see someone whose funding does NOT depend on impact hysteria (and whom
we all know and respect on 'meteorobs' :>) weighing in on this discussion.

Clear skies!
Lew Gramer

------- Forwarded Message

From: Peiser Benny <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet, 26 April 2001
Date: Thu, 26 Apr 2001 10:19:07 +0100

CCNet 60/2001 - 26 April 2001
-----------------------------

"I am convinced that only the largest of impact would have had
potential to seriously shape Human evolution: and with that
I am thinking of the very rare impacts of K/T size, which are
not likely to have happened the past 5 to 8 million years of
hominind evolution."
--Marco Langbroek, Leiden University, 25 April 2001

(1) METEORITE CRASHES NEAR MOURNING JORDANIAN VILLAGE
    Ron Baalke <baalke@jpl.nasadot gov>

(2) METEORITE OVER JORDAN?
    Mohammad Odeh <odeh@jas.org.jo>

(3) IMPACTS SHAPED EROS TOPOGRAPHY
    SpaceDaily, 24 April 2001

[...]

(7) IMPACTS & HUMAN EVOLUTION: SOME COMMENTS BY AN ARCHAEOLOGIST
    Marco Langbroek <m.langbroek@rulpre.leidenunivdot nl>

(8) IMPACTS & HUMAN EVOLUTION
    Michael Paine <mpaine@tpgi.com.au>

[...]

(14) PLAGUING COMETS
     Barbara Becker <bjbecker@UCIdot edu>

[...]

(16) MICROSTRUCTURAL SHOCK SIGNATURES OF MAJOR MINERALS IN METEORITES
     Leroux H

(17) MECHANICAL PROPERTIES OF METEORITES
     Petrovic JJ

[...]

========================================================================

(1) METEORITE CRASHES NEAR MOURNING JORDANIAN VILLAGE

Fro baalke@jpl.nasadot gov>

>From The Times of India, 24 April 2001
http://www.timesofindia.com/today/24mide3.htm

Meteorite crashes near mourning Jordanian village
AFP
April 24, 2001

AMMAN: Residents of a Jordanian village attending a funeral got an unwelcome
surprise when a fiery meteorite crashed down in their midst, one of them
said on Monday.

"More than 100 of us were gathered on Wednesday at sundown to bury a village
resident when we saw a strange object that looked like a ball of fire," said
Mohammed Nawaf Mikdadi, mayor of Beit Eidess, some 85 km north of Amman.

"The meteor shot through the sky from west to east before a part of it came
down a half km from the village, sparking an explosion and then a fire with
four-meter flames for 10 meters straight," Mikdadi said.

"The villagers thought it was a missile, but when we went to the spot there
weren't any metal scraps," he said.

The mayor expressed relief the meteorite fell on a rocky area near Beit
Eidess and not in a nearby forest, which could have spelled disaster for the
village.

(AFP)

========================================================================

(2) METEORITE OVER JORDAN?

>From Mohammad Odeh <odeh@jas.org.jo>
[as posted on the IMO mailing list]

Greetings,

Residents of a Jordanian village called Bayt Eides said that they saw a
meteorite crashed down in front of more than 100 persons of the residents.

JAS has visited the place, made an interview with an eyewitness and took
several photos for the place! To know more about this event and to see the
photos and hear the interview kindly visit JAS site at:

http://www.jas.org.jo/mett.html

Best Wishes
Moh'd
**********************************************************************
Mohammad Shawkat Odeh.
Jordanian Astronomical Society (JAS).
Member of JAS Administrative Board.
P.O. Box 925916 Amman 11110 Jordan.
Fax:  +1-707-2210918 (In USA).
Mobile: +962-79-877225
odeh@jas.org.jo
http://www.jas.org.jo/     (JAS URL)
http://jas.org.jo/wap       (JAS' WAP URL)


Meteorite Over Jordan?
By Mohammad Odeh
http://www.jas.org.jo/mett.html

On 18 April 2001 around 19:30 Local Jordanian Summer Time (UT+3), Mr. Jamal
Al-Halabi, the editor in chief of the Associated Press (who is already a
friend of JAS), called JAS member Mohammad Odeh asking him about an object
he saw in the sky from Amman few minutes ago! From his description it seemed
that what he saw was a fireball! Or better a huge fireball! Anyhow, later on
a Jordanian Newspaper mentioned that residents of a Jordanian village called
Bayt Eides saw a meteorite crashed down in front of more than 100 persons of
the residents. 

One of the eyewitnesses was Mr. Mohammad Nawwaf Miqdadi, mayor of Bayt
Eides. So JAS had directly phoned him asking him about some details, and
later on JAS decided to visit that place. 

A delegation of JAS consisting of Eng. Khalil Konsul (President of JAS),
Mohammad Odeh, and Mohammad Katbeh went to Bayt Eides on Tuesday 24 April.
JAS reached the site around 15 Local Time (LT). Where Mr. Miqdadi welcomed
JAS and joined JAS to the location. 

As JAS arrived the site, we made an interview with him asking him about the
details, and JAS took some photos, as well as determining the coordinates of
the site. According the GPS, the site is 54.4 Km to the North of Amman
(Azimuth 345). Regarding the details, Mr. Miqdadi said:- 

On Wednesday 18 April around 07 pm, which is before sunset (Sunset occurs
around 07:10 pm) at sundown to bury a village resident, more than 100
persons saw a bright object moving in the sky with a dark yellowish color.
The object was moving from west to east, and then it broke up into two
parts, which felt on a nearby hill (which is about 1.5 Km from the place at
which we were watching!). As the two pieces hit the ground we saw a fire,
initially with a greenish color, and then the fire reached up to 5 meters!
On the very next day I (Mr. Miqdadi) went to that place and I saw the two
locations at which the two parts felt. (Let's call the first location A, and
the second one B). 

Now JAS is watching and examining the location A, which no one entered yet!
The ground is full of ash and it is rather black (from the fire) and so are
the stones! What directly brought our attention were two things, the first
was a tree trunk which is broken into two parts (See Photo). Mr. Miqdadi
said this must be from the object which hit the tree! Actually the
appearance of the broken tree trunk is very strange! I don't guess it is a
man-made break! The other thing was a half burnt tree (See photo)! 

Concerning the location B, which was visited by two persons before JAS, it
was also full of ash and black. "The location was full of small rock, but
when the object hit the area it made a crater as you can see", Mr. Miqdadi
said. Actually there was no real crater! But it was clear that at certain
place the level of the rocks is lower than the surrounding, and there is a
shape of an arc. Also, a half of a large rock was burnt, while the other
half is normal (See Photo)!

We did our best to find a meteorite but I must say that we failed! So the
question is what felt then? Did the object totally burnt up? Is this ash the
meteorite remnant! Eng. Khalil Konsul said, this is not possible, because if
the ash is a meteorite remnant, then the meteorite would be very large and
this will make a real trouble! Which was not the case! 

JAS took a sample of the ash and soil. So we would be glad if the reader of
this report tell us to whom shall we send the sample for analysis ? 

Lastly, the coordinates of the of the locations are:- 

Location A:- 

Longitude: 35:42:55 E 
Latitude: 32:26:09 N 
Elevation: 707 m 
Location B (Which is about 50 meters only away of A):- 

Longitude: 35:42:56 E 
Latitude: 32:26:08 N 
Elevation: 714 m 

========================================================================

(3) IMPACTS SHAPED EROS TOPOGRAPHY

>From SpaceDaily, 24 April 2001
http://www.spacedaily.com/news/near-01n.html

Laurel - April 24, 2001

NEAR mission science team members have concluded that the majority of the
small features that make up the surface of asteroid Eros more likely came
from an unrelenting bombardment from space debris than internal processes.

Details of the research from NASA's Near Earth Asteroid Rendezvous (NEAR)
mission were published this week in Science and are based on the NEAR
Shoemaker spacecraft's Oct. 25-26, 2000, low-altitude flyover of asteroid
Eros that brought the spacecraft to within about 3 miles of the surface of
the asteroid. 

"We think that impacts to the asteroid's surface have probably been the
single-most dominant process in shaping the surface texture of the
asteroid," says NEAR Project Scientist Dr. Andrew Cheng of the Johns Hopkins
University Applied Physics Laboratory in Laurel, Md., which managed the
mission for NASA.

"We saw surface details such as regolith [surface dust and debris], craters
and fields of small boulders in incredible detail. We also saw things that
confound us, but we now have a more in-depth picture of Eros that will help
us to decipher the asteroid's history." 

During the flyover, simultaneous observations were taken by the spacecraft's
multispectral imager and laser rangefinder over two tracks approximately 1
mile and 2.5 miles long that showed objects the size of a doghouse at three
to four times better resolution than previously obtained.

The data revealed an inordinate number of small boulders, a saturation of
large craters and a dearth of small ones, crater "ponds," and unknown
erosion processes.

A vast number of large craters, 1,630 to 3,280 feet (500 to 1,000 meters) in
diameter, have been imaged, but there is a surprising scarcity of boulders
large enough to make such impacts.

There is more than 100 times the number of 10- to 12-foot (3- to 4-meter)
boulders than there are impact craters in this region. Some angular or
slab-like features were imaged that could indicate they are composed of
stronger material than rounded objects. Some boulder clusters are thought to
be fragments of a larger projectile that hit the asteroid.

The flyover also yielded evidence of an unusually low number of smaller
craters. "There could be some unknown process, possibly something like
seismic shaking following impacts, which is more likely on a small body such
as Eros," says Dr. Joseph Veverka of Cornell University, Ithaca, N.Y., who
heads the imaging team.

"Other possibilities are processes that could erode or erase smaller craters
such as micro-cratering [the pummeling of the surface by smaller objects] or
thermal creep [the erosion of surface material through normal seasonal
heating and cooling of the asteroid] that is eroding the smaller craters." 

"We do know there is a substantial amount of regolith from erosion and
impacts that is covering blocks [boulders] and craters possibly to a depth
of several meters. So it could be that many smaller craters do exist but
they're buried under the regolith," says Veverka.

"A thick covering of fine dust that prevents us from seeing what lies
beneath might also be part of the answer to why the asteroid has little
color variation. It is possible that parts of Eros are covered in regolith
as deep as a 10-story building." 

The data also revealed ponds -- flat surfaces at the bottom of craters --
formed by regolith deposits. These ponds are intriguing science team members
because of their extremely smooth surfaces.

"The smoothness indicates that there is an efficient process on Eros which
is able to sort out the finest component of the regolith from the coarser,
more blocky portion and concentrate this fine material into some low-lying
areas such as crater bottoms," Veverka says. 

Moreover, the laser altimeter found that ponded deposits are not only smooth
but also extremely horizontal -- level relative to local gravity -- as if
formed by fluid-like motions.

"It is astonishing that the total dry regolith of an asteroid like Eros can
apparently be mobilized like a fluid," says Cheng. "There is no water on
Eros, and there has not been any water, for billions of years. However,
seismic shaking caused by impacts may be able to produce fluidized movement
of regolith." 

"Aprons" of debris at the base of some of the larger boulders indicate
another phenomenon the researchers are studying: efficient erosion or
disintegration of ejecta boulders (boulders forced out of a crater as the
result of an impact) after they have landed on the surface.

But scientists say they need to study higher resolution images to more
definitively interpret the various forms of regolith that the low-altitude
images have provided. "What causes this efficient disintegration remains a
mystery," Veverka says.

"But one we hope to solve over the coming months by studying the wealth of
data that the NEAR mission has provided." 

Copyright 2001, SpaceDaily

============================
* LETTERS TO THE MODERATOR *
============================

(7) IMPACTS & HUMAN EVOLUTION: SOME COMMENTS BY AN ARCHAEOLOGIST

>From Marco Langbroek <m.langbroek@rulpre.leidenunivdot nl>

Dear Dr. Morrison, dear Dr Peiser, dear Mr Paine,

With interest I've read NEO News 4/24/01 on Impacts & Human evolution, and I
have a few points to say about this. I am a professional archaeologist
(Leiden University, faculty of Archaeology) working in the field of early
human evolution, as well as a high level amateur meteoriticist. I therefore
know both sides of the coin (human evolution & meteoritics) rather well (for
example, I am co-author to a paper on an earth-threatening comet: P.
Jenniskens et al., ApJ 479 (1997), 441-447), and certainly the Human
evolution side. Moreover, I have been pointing to a possible significant
impact with regard to early human presence in Southeast Asia in a paper
published a year ago.

As a side remark in that paper (co-authored by Wil Roebroeks) on the
chronology of the earliest human occupation of Southeast Asia, which
appeared in April 2000 (M. Langbroek & W. Roebroeks: J. Human Evolution 38
(2000), 595-600), in which tektites were an argument, I've pointed out that
a large impact, believed by some to be one of the largest of the past few
million years, occurred in SE Asia 0.8 Ma ago, and that it was of such a
magnitude that it "must have had serious consequences for the
palaeo-environment and biogeographical history (perhaps including local
hominid evolution) of Southeast Asia".

This topic is discussed in more detail in my 1998 Master dissertation, and
will be discussed in more detail in an appendix to my upcoming PhD
dissertation. The impact in question is the impact which created the large
Australasian tektite strewnfield. It is extremely well dated at 0.80 Ma (see
our paper and refs therein). This is well within the time span of human
evolution, and moreover, humans might have been present near or in the
actual impact affected area. The impact is believed to have occurred in the
area of Laos, Cambodia or Thailand, from multiple lines of evidence. Schmidt
& Wasson (Meteoritics 28 (1993), 430) have, from the strewnfield structure,
estimated the strewnfield to be caused by an impact with an energy release
in the order of 5x10^4 to 1x10^5 MT. In the impact hazard assessment model
of Chapman and Morrison (Nature 367 (1994), 33-39), this would be an impact
at the lower limit of the "global effects threshold". Apart from possible
short term effects due to atmospheric dust release, ozone depletion and acid
rains, employing the simple scaling relationships from the Chapman and
Morrison paper also shows that an area of about 150 000 to 200 000 square
kilometer, or an area 500 kilometer in diameter, would be directly affected
by air blast phenomena. Such an area is significant in size: it amounts to
as much as about one third of the longitudinal diameter of the Southeast
Asian peninsula/Sunda shelf at this location. In a larger area of Indochina
roughly 1000 km in size, impact ejecta in the form of large Muong-Nong type
tektites occur. These are believed to have been still plastic and "hot" upon
landing (Fiske, Met. Plan. Sci. 31 (1996), 42-44), creating the possibility
that they started wildfires within this large area which covers a
significant part of the Indochinean peninsula. This is considerable
ecological havoc on a sub-continental scale.

We know that hominids were present in China at about 1.1-1.2 Ma, well before
the impact. Debates are currently raging (and I am in the thick of it)
concerning the earliest occupation of Southeast Asia. Some would have it as
early as 1.8 Ma, which I strongly doubt (see our 2000 JHE paper). But even
my more conservative estimate brings humans in Indonesia at about 1.1 Ma,
which still is before the impact. To get to Indonesia, they had to cross the
area of impact first, hence the impact area would probably have been
"settled" in a broad sense. Yet evidence from the actual impact area
(Cambodia-Laos,Vietnam, Thailand) dating from the time of impact is actually
absent. This seems to have a geological reason as not only traces of human
presence, but faunal assemblages in general are lacking from this area from
this time span: in addition, there is the enigmatic point that the impact
crater itself has not been positively identified yet. This indicates that
deposits from this time span have become inaccessible due to (probably) some
geological reason. Uncertainties concerning the chronology of Quaternary
Sunda make it currently impossible to tie biogeographic events on the Sunda
shelf south of the impact area with possible effects of the impact.

While very significant on a sub-continental scale (which is thus not to be
ignored!) and perhaps (and inevitably if they indeed were present in the
actual impact affected area) leading to the extinction of a local subgroup
of Homo erectus, there is NO evidence that this lead to long term effects in
whatever way, notwithstanding that this was one of the largest impacts in
the time span of human evolution. Detailed study of Deep Ocean Drilling Core
data by Schneider, Kent & Mello (Earth Planet. Sci. Lett. 111 (1992),
395-405) revealed no evidence for significant climatic perturbations on a
timescale of 1 ka: compared with the strong effects of glacial cycles, this
impact was hardly a ripple in the ocean. Likewise, even if local Homo
erectus inhabitants of the impact area were wiped out (as seems likely) on a
sub continental scale, this seems to have had little evolutionary effects.
Once the dust settled, the population was simply restocked by Homo erectus
from outside the impact-affected area. Such abandonment and repopulations of
areas probably were common in the Pleistocene, certainly in this area,
connected to events that had nothing to do with impact but where of similar
scales or even scales surpassing the short-term effects of impact: for
example the strong effects of cyclical flooding and re-emergence of the
Sunda shelf just south of the impact area, due to the cycles of sea-level
change connected to the glacial cycles: or the known waxing and waning of
the Human population of Europe over time (e.g. the depopulation of large
parts of Europe during the height of the last glacial 18 000 years ago) as a
result of the glacial cycles.

This brings me to a concern with the picture such as painted by Peiser and
Paine. I am convinced that only the largest of impact would have had
potential to seriously shape Human evolution: and with that I am thinking of
the very rare impacts of K/T size, which are not likely to have happened the
past 5 to 8 million years of hominine evolution (and at any rate, such an
impact would have yielded clearly discernable signs in the geological and
palaeontological record, in the form of mass extinctions of a considerable
part of the global fauna and flora, as well as widespread (=global) presence
of impact ejecta). Any smaller impacts will simply have had effects which
were insignificant compared to the powerful driving force of the glacial
cycles of the last few million years. Effects would have been very local and
temporary when seen in that context, being hardly more than ripples in the
ocean, whereby an area was temporarily depopulated and then repopulated
again. Where climatic effects (and by inference ecological effects) stay
short-term and do not wipe out significant parts of the global or
continental biomass (and there is no evidence for such non-short term,
non-local effects due to impact in palaeoclimatological and biochronological
proxy data of the past million years, while these effects should be
discernable if they happened), evolutionary effects are very minor and such
things will not lead to profound speciation. As Steve Drury very rightly
pointed out in his comment, Peiser and Paine make a mistake in focusing on
hominid EXTINCTION: what really drove human evolution was an unbound hominid
SPECIATION during the Pliocene and Pleistocene. In the absence of a near
continental ecological wipe-out, which we know did not happen, such
phenomena can come about only through long term trends of ecological
diversification on a large geographic scale, as happened in Africa when a
trend of aridification and increasing seasonality set in at the end of the
Miocene, with some profound accelerations near 2.5 and 1.8 Ma, creating long
term change in the ecology and new directions of ecological developments. In
this sense, I am a bit afraid that Peisser and Paine seem to be ignorant of
what evolution really amounts to. The extinctions they focus upon where an
unimportant side effect created by speciation: hominine species only could
become extinct because they had been created by speciation first, and when
ecological diversification due to long term trends in ecological change
creates speciation events, there inevitably have to be a series of
extinctions following too. Many of the large number of hominine species
Peiser and Paine point out got extinct during the Pliocene and Pleistocene,
were species that were chronologically contemporary, sharing a similar time
span and in general a similar geographical area and grosso modo similar
structured ecology: but filling slightly differing niches within that grosso
modo similar ecology and geographic area. It were long-term changes in the
details of ecological structure which drove evolutionary selection: while on
the other hand an impact of the necessary continental scale (Pliocene
African Australopithecines at 3.5 Ma for example where present in an area
ranging from South Africa via East Africa to Chad!)would have wiped them out
all at once, along with many other mammalian species which emerged and
evolved during the same time span in the same area due to the same
evolutionary processes. That should leave its signs in the record, and the
signs are not there. Therefore, I really strongly doubt whether cosmic
impacts played a major significant role in Human evolution of the past 5 to
8 million years.

Sincerely,

Marco Langbroek
Palaeolithic Archaeologist
Faculty of Archaeology
Leiden University
P.O. Box 9515
NL-2300 RA Leiden
the Netherlands

building 1176, room 021
tel. +31 (0)71 5272926
fax  +31 (0)71 5272429
e-mail: m.langbroek@arch.leidenunivdot nl
private: marco.langbroek@wanadoodot nl


MODERATOR'S NOTE: I very much welcome Marco Langbroek's comments and
critique. Michael and I have now started to write up our hypothesis as a
scientific paper for publication in a peer-reviewed journal. Nevertheless,
we intend to respond in greater detail to Marco's objections and
assumptions, as well as those by other critics, by next week. BJP

========================================================================

(8) IMPACTS & HUMAN EVOLUTION

>From Michael Paine <mpaine@tpgi.com.au>

Dear Marco,

Thank you for your comprehensive comments on the issue of impacts and human
evolution. I will study them in details over the next few days but offer a
few quick comments.

I too have looked (briefly) at the 800Ka tektite event in SE Asia and I
prepared a popular-level paper on the subject that was published in the
February 2001 issue of Meteorite. A preprint available at
http://www4.tpg.com.au/users/tps-seti/climate.htm along with a table of
possible environmental effects of impacts. I am an amateur in this field and
do not have good access to resources but I wish I had come across your paper
(do you have an electronic copy that you could send me?). I too am puzzled
by the appearent lack of global effects associated with this event. 

There are several possible confounding factors

* 	It is possible that the assumptions about the size of the impact,
based on the tektite 	strewn field, are wrong.

* 	The severe climate consequences would have lasted for a few years,
perhaps decades but 	the sensitivity of climate analysis techniques is of
the order of centuries (as you point 	out "no evidence for significant
climatic perturbations on a timescale of 1 ka"). 

* 	Similarly a layer of dust/clay from an impact by a 2km diameter
asteroid would only be 	about 10 microns thick and probably go undetected
(rough calculation by Alan Haris from JPL 	by scaling the KT event).

* 	I understand that archaeological dating over this period is very
difficult.

* 	The estimates of environmental effects, as set out by Toon and
others (Toon, O.B., K. 	Zahnle, D. Morrison, R.P. Turco, and C. Covey:
Environmental pertubations caused by the 	impacts of asteroids and
comets. Reviews of Geophysics 35:41-78 (1997) could be too 	pessimistic.
There appears to be no easy way to verify some of these predictions. Dr Jay
Melosh from Uni Arizona has expressed to me concerns about uncertainty in
environmental 	predictions.

Subject to this uncertainty, while the environmental consequences of a 2km
impact only last a few years it could be expected to have a severe effect on
the biosphere, just as it would on today's human population. However, like
the climate record, I doubt if the fossil record is sufficiently sensitive
to show up such disruptions. After all, would we have known about the Black
Death and other major plagues through RECORDED history on the basis of
archaeological evidence alone and yet the human population was decimated at
these times.

I have attached a graph that shows impact events and hominid lines that I
prepared yesterday, after reading the Space.com article by Rob Britt.

There is much to be done in this fascinating field.

regards
Michael Paine

========================================================================

(14) PLAGUING COMETS

>From Barbara Becker <bjbecker@UCIdot edu>
as posted on the HASTRO-L@WVNVM.WVNETdot edu mailing list

Hi everyone! 

Another astronomical question has arisen in my plagues class, this one
related to a different plague and a different comet. 

In Book XII of his remarkable _General History of the Things of New Spain_,
Fray Bernardino de Sahagun tells of 8 omens observed by the Mexica before
the arrival of Hernando Cortes. 

The first (although the word "comet" is not used) seems to me to describe a
comet. The exact year of its apparition is somewhat unclear since it is
variously stated that it appeared ten years before the arrival of the
Spaniards and elsewhere that it appeared two years before. 

"Comet" is used to describe the fourth omen, but it sounds more like a
bolide. I'll provide the text for both omens below. 

I've used "Redshift" and located a comet that would have appeared on or
above the horizon in Mexico City at midnight from April to August 1506 (a
little more than ten years before Cortes' arrival). The program contains no
ephemerides for a comet in 1517. 

Roberta Olsen, in _Fire and Ice: A History of Comets in Art_, mentions (but
doesn't provide) a European illustration of a 1506 comet (on p. 36). On p.
46, she shows the illustration from Duran's _Historia de las Indias...._
which depicts "Montezuma transfixed by a comet in 1519-20". 

My question is: does anyone have information about comets recorded or
illustrated around that time -- or possibly a periodic comet that might have
gone unrecorded in Europe but might have made a favorable apparition in
lower latitudes? 

Here are the quotes from Sahagun: 

	When the Spaniards had not arrived, by ten years, an omen first
appeared in the heavens. It 	was like a tongue of fire, like a flame, as
if showering the light of the dawn. It looked 	as if it were piercing the
heavens. [It was] wide at the base and pointed [at the head]. To 	the
very midst of the sky, to the very heart of the heavens it extended; to the
very 	midpoint of the skies stood stretched that which was seen off to the
east. When it arose 	and thus came forth, when it appeared at midnight,
it looked as if day had dawned. When day 	broke, later, the sun
destroyed it when he arose. For a full year [the sign] came forth. 	(It
was [in the year] Twelve House that it began.) [1517] And when it appeared,
there was 	shouting; all cried out striking the palm of the hand
against the mouth. All were 	frightened and waited with dread.... 

	A fourth omen: there was yet sun when a comet fell. It became three
parts. It departed from 	where the sun set and traveled toward where
he came forth. As if sprinkling live coals, 	[so] its tail went extended
a great distance. Far did its tail reach. And when it was seen,
great was the uproar; like [the din of] shell rattles [the outcry] was
overspread.... 

For any of you who are interested, here's the URL for the Plagues course
website that I've been building: http://e3.ucidot edu/01s/28145/index.html 

It's still under construction, so check back periodically. 

Here's the URL for the website I made last quarter for the introduction to
history of science survey course. There are some astronomical history
documents on it that you may find interesting and/or useful:
http://e3.ucidot edu/01w/28140/index.html 

Thanks in advance!! 

best, 

"Comet-ose" Barb. 

=============
* ABSTRACTS *
=============

(16) MICROSTRUCTURAL SHOCK SIGNATURES OF MAJOR MINERALS IN METEORITES

Leroux H: Microstructural shock signatures of major minerals in meteorites
EUROPEAN JOURNAL OF MINERALOGY 13 (2): 253-272 MAR-APR 2001

Shock metamorphism is a fundamental process in the solar system. It is
evidenced by craters on the surfaces of solid planets and asteroids, as well
as by shock-induced microstructural modifications in minerals. This paper
presents review of the main microstructural characteristics of shock
signatures in meteoritic minerals (olivine, enstatite, diopside, plagioclase
and metal) as evidenced by transmission electron microscopy (TEM). The
nature of the shock-induced modifications strongly depends on the material
and the shock conditions (peak pressure and peak temperature). It includes
fracturing, dislocations and twins (evidence of plastic deformation), phase
transformation to high pressure polymorphs, amorphization,
recrystallization, melting and volatilization. The influence of
shock-induced microstructures during post-shock events is also discussed and
further research tracks on the microstructural aspect of shock metamorphism
are outlined.

Addresses:
Leroux H, Univ Sci & Technol Lille, Lab Struct & Proproetes Etat Solide,
CNRS, ESA 8008, F-59655 Villeneuve Dascq, France
Univ Sci & Technol Lille, Lab Struct & Proproetes Etat Solide, CNRS, ESA
8008, F-59655 Villeneuve Dascq, France

Copyright ) 2001 Institute for Scientific Information

==================================================================

(17) MECHANICAL PROPERTIES OF METEORITES

Petrovic JJ: Mechanical properties of meteorites and their constituents
JOURNAL OF MATERIALS SCIENCE 36 (7): 1579-1583 APR 2001

A review is presented of the mechanical properties of meteorites and
meteorite constituents. Scientific literature data on the strength of stony
and iron meteorites are extremely limited. The average mechanically-measured
stony meteorite compressive strength is 200 MPa, while the average iron
meteorite compressive strength is 430 MPa. However, the best current
estimate of the strength of stony bodies in space may be in the range of
only 1-5 MPa, based on observations of meteorite fragmentation due to
dynamic atmospheric loading upon Earth entry. Mechanical property and
behavior information on both iron-nickel alloy and mineral meteorite
constituents is also surprisingly limited in the metallurgical, rock
mechanics, and ceramics literature. (C) 2001 Kluwer Academic Publishers.

Addresses:
Petrovic JJ, Univ Calif Los Alamos Natl Lab, Div Mat Sci & Technol, Los
Alamos, NM 87545 USA
Univ Calif Los Alamos Natl Lab, Div Mat Sci & Technol, Los Alamos, NM 87545
USA

Copyright ) 2001 Institute for Scientific Information

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