PLEASE NOTE:
*
CCNet, 65/2000 - 6 June 2000
-----------------------------
"I can't help feeling that
this [Gaia] story is a major
beef-up... a couple of weeks ago,
I drew Michael Paine's
attentions to similar NEO
detection claims being made for the
BepiColumbo Mercury Orbiter which
is GAIA's competition for the
next Cornerstone mission launch.
GAIA will at best do incidental
asteroid detection on the margins
of its main work. Since there's
no evidence to suggest that GAIA
is being retooled in any way for
NEO detection, I wonder why this
PR push has suddenly begun."
-- Robert Clements
(1) ISRAELI SCIENTISTS PROPOSE NEW ORIGIN-OF-LIFE THEORY
Andrew Yee <ayee@nova.astro.utoronto.ca>
(2) ANCIENT GREEK CITIES DESTROYED BY FLOOD DISASTER?
ABC News, 3 June 2000
(3) NOBLE GAS DETECTED IN COMET HALE-BOPP
Andrew Yee <ayee@nova.astro.utoronto.ca>
(4) ETA AQUARID METEOR SHOWER
Mark Davis <meteorobs@charleston.net>
(5) OPINION: WHY THIS SUDDEN PR FOR SPURIOUS NEO PROJECTS?
Robert Clements <Robert.Clements@dva.gov.au>
(6) IMPACT CRATER OIL FINDS
Ed Grondine <epgrondine@yahoo.com>
(7) FROST MOUNDS DETECTED ON MARS?
N.A. Cabrol et al., NASA,AMES RES CTR
(8) ELLIPTICAL CRATERS ON MARS, VENUS AND MOON
W.F. Bottke et al., CORNELL UNIVERSITY
(9) MARE SOILS & CRATERS
M.I. Staid*) & C.M. Pieters, BROWN
UNIVERSITY
(10) COLLISION RATES IN THE KUIPER BELT & CENTAUR REGIONS
D.D. Durda & S.A. Stern, SW RES
INST,SPACE STUDIES DEPT
(11) MELT PRODUCTION IN OBLIQUE IMPACTS
E. Pierazzo & H.J. Melosh, *)
UNIVERSITY OF ARIZONA
(12) AND FINALLY: APOCALYPTIC DESIRE FOR GREEN DICTATORSHIP &
GLOBAL MASS STARVATION
National Post, 3 June 2000
===============
(1) ISRAELI SCIENTISTS PROPOSE NEW ORIGIN-OF-LIFE THEORY
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Weizmann Institute of Science
Rehovot, Israel
Press Inquiries:
Yivsam Azgad
tel. 972 8 934 3852/6, fax: 972 8 934 4132
e-mail: yivsam.azgad@weizmann.ac.il
For Immediate Release: June 5, 2000
Scientists At The Weizmann Institute Propose A New Theory To The
Mystery Of The Origin Of Life
One of the greatest mysteries, which continuously fascinate many
scientists worldwide, concerns the way by which life emerged on
primeval Earth. The accepted notion is that prior to the
appearance of
living organisms, there was a stage of chemical evolution, which
involved selection within inanimate chemical mixtures. This is
thought
to have eventually led to the crucial moment, when
self-replicating
molecules arose. As self-replication is a most fundamental
characteristic of living entities, such an event is often defined
as
the birth of life.
Self-replication of molecular systems is often viewed in the
context of
information content. Many scientists believe that life began with
the
spontaneous emergence of biopolymers, such as proteins or RNA,
where
information is stored in the sequence of chemical units.
Experiments
mimicking the conditions on Earth billions of years ago have
shown how
such chemical units, e.g. some of the building blocks of proteins
and
RNA, could appear spontaneously. Yet, the emergence of proteins
or
self-replicating RNA molecules remained enigmatic.
This started Prof. Doron Lancet of the Molecular Genetics
Department in
the Weizmann Institute of Science, and his students, Daniel Segre
and
Dafna Ben-Eli, on a journey leading to alternatives to proteins
and
RNA. They have developed a model, suggesting a new route for the
origin
of life, based on lipid molecules. This model is described in an
article published a recent issue of the Proceedings of the
National
Academy of Science, USA.
Lipids are oily substances, known as chief ingredients of the
cell's
membranes. Lipids have two different aspects -- one hydrophilic
(water-
attracting), and the other hydrophobic (water-repelling). They
get
readily synthesized under simulated prebiological conditions, and
because of their bipartite nature, have the tendency to
spontaneously
form supramolecular structures made of thousands of molecular
units.
This is exemplified in lipid assemblies (micelles), which have
even
been shown to be capable of growing and splitting in a fashion
reminiscent of cell replication. Yet a critical question was left
unanswered: how could lipid assemblies carry and propagate
information?
The model proposed by Lancet and colleagues offers a solution.
They
surmise that early on, lipid-like compounds existed in a very
large
diversity of shapes and forms. They show mathematically that
under such
conditions, lipid assemblies could contain almost as much
information
as an RNA strand or a protein chain. Information would be stored
in the
assembly's composition, i.e. in the exact amount of each of its
compounds, rather than in a sequence of molecular 'beads' on a
string.
A useful analogy would be that of perfume: the information -- the
scent
as discerned by receptors in the nose -- depends on each
ingredient's
proportion in the mixture, but the order in which aromas are
added is
unimportant.
Thus, the authors argue, heterogeneous lipid assemblies may be
thought
of as having a 'compositional genome'. They further demonstrate
how a
droplet-like lipid assembly, when growing and splitting, could
manifest
a form of inheritance. Their computer simulations show how a
compositional genome would be handed down with some fidelity to
the
offspring assemblies. A crucial aspect of the model is how such
molecular inheritance is made possible. In present-day cells, the
replication of information-containing DNA is facilitated by
protein
enzyme catalysts. In the early prebiological era, catalysis could
be
performed by the same lipid-like substances that carry the
information.
Molecules already present inside a droplet would function as a
molecular selection committee, enhancing the rate of entry for
some,
and rejecting others.
Lancet, Segre, and Ben-Eli designed a computerized simulation
that
shows how, based solely on physiochemical principles, lipid
droplets
with idiosyncratic compositions accrete, grow, split,
self-replicate,
accumulate compositional mutations, and get involved in a complex
evolutionary game. Importantly, it is entire assemblies, with
their
complex mixtures of relatively small molecules that are
replicated.
This differs from the older models, in which a single, long RNA
polymer
is what gets copied. The scientists' model makes very few
chemical
assumptions and derives a rich molecular behavior reminiscent of
life
processes. It therefore has the potential of constituting the
long-sought bridge leading from the inanimate world to that of
living
organisms.
This research has already attracted considerable interest, and
was
quoted in the recently published new edition of the classic book
Origins of Life by Freeman Dyson from the Princeton Institute of
Advanced Study. The next important question to be answered: how
could
lipid droplets undergo the numerous transitions needed to lead to
living cells as we now know them? In this sense, the study marks
the
first footfall in a long journey to come.
Professor Lancet holds the Ralph and Lois Silver Professorial
Chair in
Neurogenomics.
============
(2) ANCIENT GREEK CITIES DESTROYED BY FLOOD DISASTER?
From ABC News, 3 June 2000
http://abcnews.go.com/sections/world/DailyNews/cities000603.html
Land of the Lost: Archaeologists Discover Ancient Cities Under
Mediterranean
By Vijay Joshi
The Associated Press
A L E X A N D R I A, Egypt, June 3 — Archaeologists scouring
the
Mediterranean seabed announced today they have found the
2,500-year-old
ruins of submerged Pharaonic cities that until now were known
only
through Greek tragedies, travelogues and legends.
Among the stunning discoveries at the sites—where the cities
of
Herakleion, Canopus and Menouthis once stood—are remarkably
preserved
houses, temples, port infrastructure and colossal statues that
stand
testimony to the citizens’ luxuriant lifestyle, which some
travelers
had described as decadent.
This is the first time that historians have found physical
evidence of
the existence of the lost cities, which were famous not only for
their
riches and arts, but also for numerous temples dedicated to the
gods
Isis, Serapis and Osiris, making the region an important
pilgrimage
destination for various cults.
Herakleion, once a customs port where commerce flourished until
the
founding of Alexandria by Alexander the Great in 331 B.C., was
found in
its entirety.
‘Frozen In Time’
"We have an intact city, frozen in time," said Franck
Goddio, a French
archaeologist who led the international team in the search.
The team worked for two years off this city on Egypt’s
northern coast
in waters 20 to 30 feet deep, using modern technology including
the use
of magnetic waves to map the area.
"It is the most exciting find in the history of marine
archaeology. It
has shown that land is not enough for Egyptian antiquities,"
said
Gaballa Ali Gaballa, secretary-general of the Supreme Council of
Antiquities, Egypt’s top archaeology body.
At a news conference, underwater television footage of the site
was
shown to reporters. Some of the treasure was also on display
— a basalt
head of a pharaoh, a bust of the curly haired and bearded god
Serapis
and a life-size headless black granite statue of the goddess
Isis,
sculpted as if wearing a diaphanous cloth held together by knots
at her
breast.
Cities Of Myth Built Millennia Ago
"At long last, these lost cities of Menouthis and Herakleion
have been
located,” said Gaballa. He said the cities—probably
built during the
waning days of the pharaohs in the 7th or 6th century B.C.—will
be left
as they are in the sea and only smaller pieces will be retrieved
for
museums.
Numerous ancient texts speak of the importance of the region and
the
cities, before they were covered over by the sea, probably
following an
earthquake.
Greek historian Herodotus, who visited Egypt in 450 B.C., wrote
about
Herakleion and its temple dedicated to Hercules. The sites were
also
named in Greek tragedies—Greek mythology tells the story of
Menelaos,
king of Spartans, who stopped in Herakleion during his return
from Troy
with Helena. His helmsman Canopus was bitten by a viper and
subsequently transformed into a god. Canopus and his wife
Menouthis
were immortalized by two cities that bore their names.
Authors such as Strabo describe the geographic location of the
cities
and their rich lifestyle, while others, such as Seneca, condemn
their
moral corruption.
Herakleion lost its economic importance after the building of
Alexandria. It was probably destroyed by an earthquake, indicated
by
the position of collapsed columns and walls. They had all fallen
systematically in one direction, said [CCNet list member] Amos
Nur, a
geophysicist from Stanford University who did the magnetic
mapping of
the area.
The sea encroached on the land following the quake, and ruins of
Herakleion are now about four miles from land in the Bay of Abu
Qir.
The sea also engulfed Canopus and Menouthis.
The destruction most likely happened in the 7th or 8th century.
Divers
found Islamic and Byzantine coins and jewelry from that period,
but
none more recent.
Copyright 2000 The Associated Press
==================
(3) NOBLE GAS DETECTED IN COMET HALE-BOPP
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Southwest Research Institute (SwRI) News
For release after 10:00 a.m. EDT, June 5, 2000
Astronomers report the first detection of a noble gas in a comet
and
new clues to the origin of Hale-Bopp
San Antonio, June 5, 2000 -- Astronomers announced today at the
American Astronomical Society meeting in Rochester, New York,
that they
have detected argon, a scientifically valuable noble gas, in
comet
Hale-Bopp. This discovery constitutes the first-ever detection of
a
noble gas in a comet. Noble gases provide valuable tracers of the
thermal history and, therefore, clues to the origins of comets.
The discovery was made by a team of four astronomers from
Southwest
Research Instituteª (SwRI), based in San Antonio, Texas,
collaborating
with three colleagues from the University of Colorado, the
University
of Maryland, and the Observatoire de Midi-Pyrenees in France. The
study
was supported by NASA.
The data on comet Hale-Bopp were obtained in the form of
ultraviolet
spectra during a NASA high-altitude suborbital research rocket
flight
on the evening of March 29, 1997, just as comet Hale-Bopp made
its
closest approach to the sun. According to team leader and
Principal
Investigator Dr. Alan Stern, director of the SwRI Space Studies
Department, "The argon signals are weak, but unmistakable.
We had
previously suspected their presence, but were able to recently
confirm
the result when we cross-compared two independent spectra
obtained by
our rocket instrument back in 1997."
Adds co-investigator Dr. David Slater, a senior research
scientist at
SwRI, "Hale-Bopp was among the brightest comets ever
witnessed, and
surely the brightest comet in modern times. The detection of
argon
would not have been possible except for Hale-Bopp's unusually
high
brightness."
Because noble gases do not interact chemically with other
elements and
because noble gases are easily lost from icy bodies like comets
at very
low temperatures through processes much like evaporation, their
presence or absence provides a way of measuring the thermal
history of
comets. University of Maryland astronomer and team member Dr.
Michael
A'Hearn explains, "That's the reason cometary astronomers
have wanted
to detect noble gases for so long. The advance of technology
combined
with the brightness of Hale-Bopp made this goal a reality."
Interestingly, the team's spectra showed that the argon abundance
in
Hale-Bopp was so high that it indicates the comet has always been
quite
cold and likely formed in the deep outer reaches of the solar
system,
far beyond its once-suspected birthplace in the somewhat warmer
Jupiter
zone. "Our results indicate that Hale-Bopp was likely formed
in the
Uranus-Neptune zone," says Stern. The high argon abundance
of Hale-Bopp
may also help explain the unexpected findings by the Galileo
Jupiter
entry probe, which found that Jupiter has an argon abundance
similar to
comet Hale-Bopp. "Perhaps Jupiter was seeded with extra
argon by the
impact of many comets like Hale-Bopp early in the history of the
solar
system," remarks Stern.
The detection of argon in Hale-Bopp has whet the scientists'
appetite
for more noble gas data on comets. The team is preparing an
instrument
called the ALICE Ultraviolet Spectrometer for NASA to fly to
comet
Wirtanen aboard the European-U.S. Rosetta comet orbiter mission
to be
launched in 2003. The team has proposed a series of additional
NASA
rocket launches in 2002 and 2003 to search for argon and other
noble
gases, even before the Wirtanen orbiter mission is launched.
Stern
says, "Using this even more sensitive generation of
instruments, we
look forward to comparing different comets to one another to
learn
about the diversity of cometary birthplaces."
For more information about the origin of Hale-Bopp, contact Maria
Martinez, Communications Department, Southwest Research
Institute, P.O.
Drawer 28510, San Antonio, Texas, 78228-0510, Phone (210)
522-3305,
Fax (210) 522-3547.
===================
(4) ETA AQUARID METEOR SHOWER
From Mark Davis <meteorobs@charleston.net>
North American Meteor Network
Results of May Observations
During the month of May, NAMN concentrated its efforts on the Eta
Aquarid meteor shower. Some consider this the sister shower of
the
Orionids of October as both the Orionids and Eta Aquarids have
Comet
Halley as their parent. The May sibling is better placed for
observers
at more southerly latitudes as the radiant at maximum is at -01
degrees
declination. Observers who monitor this shower are often rewarded
with
fast and bright meteors the last hour or two before sunrise. This
year
we again participated with the International Meteor Organization
in
collecting observations of the Eta Aquarids (see IMO Shower
Circular -
Eta-AQUARIDS 2000 -- I & II).
The month of May opened with Eta Aquarids being reported on the
1st by
Robin Gray, Robert Lunsford and Norman McLeod. The next six
mornings
were covered with rates generally lower than 5 per hour.
Exceptions to
this were Robert Goler on May 2 (avg. 7.8/hour); Kim Youmans
(avg.
5.5/hour) on May 3; Michael Mattiazzo (avg. 10.5/hour), Norman
McLeod
(avg. 7.1/hour), Mark Davis (avg. 5.3/hour), Robert Lunsford
(avg.
7.0/hour) on May 4; John Drummond (avg. 5.9/hour), Kim Youmans
(avg.
7.3/hour), Scott Moser (avg. 5.0/hour) on May 5; Mike Linnolt
(avg.
8.5/hour) on May 6; Kim Youmans (avg. 5.4/hour), Norman McLeod
(avg.
10.5/hour) on May 7. Other observers reporting Eta Aquarids in
May (at
lower rates, often away from the peak) include: Jure Atanackov,
Asdai
Diaz, Robin Gray, Pierre Martin, Erick Mota, Harry Waldron and
Jin Zhu.
The second most active shower during the month was the
Sagittarids.
Several radiants in the Scorpius and Sagittarius region of the
sky were
combined into this one shower by the International Meteor
Organization
several years ago. Therefore, they have a long activity period
ranging
from mid-April into mid-July with rates never reaching more than
about
5 per hour at the most. Their maximum is normally considered to
occur
around May 20th. Throughout this month, most of our observers
were able
to record at least a few of these meteors. The highest average
hourly
rate was 2.85 as reported by Asdai Diaz on May 6.
As can be seen in the shower list below, there were several minor
streams that exhibited a limited amount of activity during the
month.
These showers are normally followed by observers utilizing
plotting
techniques. Observers, and the showers they monitored, include:
Jure
Atanackov (ABO, MVI); Robin Gray (MVI); Mike Linnolt (ABO, ASC,
CAU,
MVI); Pierre Martin (ABO, MVI, OCA); Norman McLeod (ABO, FBO,
MVI);
James Smith (ABO, ASC, FBO, MVI) and Kim Youmans (ABO).
In all, 19 observers submitted reports for the month of May.
These
included:
Jure Atanackov
(Slovenia)
Michael Mattiazzo (Australia)
Mark Davis (United
States)
Norman McLeod (United States)
Asdai Diaz
(Cuba)
Scott Moser (United States)
John Drummond (New
Zealand)
Erick Mota (Cuba)
Robert Goler
(Australia)
James Smith (Canada)
Robin Gray (United
States)
Harry Waldron (United States)
Javor Kac
(Slovenia)
Kim Youmans (United States)
Mike Linnolt (United
States)
Jure Zakrajsck (Slovenia)
Robert Lunsford (United
States) Jin Zhu
(China)
Pierre Martin (Canada)
Showers observed, and the number of each recorded during over 90
hours
of effective observing time in May include:
Shower
Number Observed
ABO - Alpha
Bootids
9
ASC - Alpha
Scorpiids
9
CAU - Beta Corona
Australis
3
ETA - Eta
Aquarids
242
FBO - Phi
Bootids
2
MVI - Mu
Virginids
14
OCA - Omega
Capricornids
2
SAG -
Sagittarids
50
SPO -
Sporadics
666
For those interested in a complete listing of observations, visit
the
"Recent Observations" section of the NAMN website at
http://web.infoave.net/~meteorobs.
There you will find reports broken
down into observing periods.
Thanks to all observers who contributed reports this past month,
and
clear skies in June!!
Mark Davis
NAMN Coordinator
=================
(5) OPINION: WHY THIS SUDDEN PR FOR SPURIOUS NEO PROJECTS?
From Robert Clements <Robert.Clements@dva.gov.au>
Re: ANOTHER NEO-CASTLE IN THE AIR
http://www.observer.co.uk/uk_news/story/0,6903,319399,00.html
I can't help feeling that this story is a major beef-up... a
couple of
weeks ago, i drew Michael Paine's attentions to similar NEO
detection
claims being made for the BepiColumbo Mercury Orbiter which is
GAIA's
competition for the next Cornerstone mission launch.
GAIA is ESA's shot at a postHipparchos starmapper (url:
http://www.sci.esa.int/home/gaia/)
which will at best do incidental
asteroid detection on the margins of its main work; & as far
as i can
make out (although this is probably an oversimplification on my
part),
it's simply a bigger version of NASA's FAME (url:
http://aa.usno.navy.mil/FAME/).
Since there's no evidence to suggest
that GAIA is being retooled in any way for NEO detection, i
wonder why
this pr push has suddenly begun... & for that matter: can
FAME also be
incidentally used for NEO detection?
Unless these missions are prepared to offer real time to NEO
detection
operations, they shouldn't be using the impactor issue to
justifying
their expenditures.
All the best,
Robert Clements <Robert.Clements@dva.gov.au>
==================
(6) IMPACT CRATER OIL FINDS
From Ed Grondine <epgrondine@yahoo.com>
Forwarded from <meteorite-list@meteoritecentral.com>
DIPPING INTO CRATER POOLS
Canadian Geographic: May/June 1995
Terrence Dickenson
Canada's landscape bears the scars of 26 of the world's 144 known
impact craters- more then any other country. Most of the are
buried too
deeply to offer any economical ore-extracting potential. (The
great
exception, of course is the crater at Sudbury, Ont., which is the
richest deposit of nickel in the world.) But deeper craters do
create
effective traps for somthing equally prized: oil.
The fractured rocks beneath a crater create a perfect storage
facility
for oil, explains Kirk Osadetz of the Geological Survey's
Institue of
Sedimentary and Petroleum Geology in Calgary. "Once the
impact
structure is covered by sedimentary rock, it becomes a natural
petroleum reservoir." The crater rim and its central area
are
especially heavily ruptured zones of cracks and fissures, where
oil
tends to migrate and remain.
"The impact itself doesn't create any oil," says impact
crater
specialist Richard Grieve of the Geological Survery of Canada. If
the
oil is already there, the impact structure can provide the
reservoir.
Or if the oil is produced later, it may migrate to a nearby
crater.
Although the majority of Canada's craters are in the ancient
rocks of
the Canadian Shield, Grieve says the Shield was never buried
deeply
enough by sedimentary to allow this process to work.
Two buried craters have been identified in Canada's western oil
patch,
one in norht-western Alberta, one is Saskatchewn. Petrolem
geologists
have taken more-than-casual interest in these structures since
it became known that the highest-producing oil well in Oklahoma
sits on
an ancient buried impact crater. Grieve suspects that some of
Alberta's
best wells could be extracting oil from impact structure
reservoirs
that have yet to be identified as such.
Grieve estimates that $5 billion worth of oil and minerals -
which
would otherwise be more difficult to access - are extracted
from
craters every year in North America. He adds " Many
impact structures
remain to be discovered or exploited".
Copyright 1995, Canadian Geographic
==============
(7) FROST MOUNDS DETECTED ON MARS?
N.A. Cabrol*), E.A. Grin, W.H. Pollard: Possible frost mounds in
an
ancient Martian lake bed. ICARUS, 2000, Vol.145, No.1, pp.91-107
*) NASA,AMES RES CTR,SETI INST,DIV SPACE SCI,MOFFETT
FIELD,CA,94035
Circular to elongated mounds are observed in Gusev crater in the
Aeolis
subquadrangle of Mars. They are arranged in a large cluster and
show
different stages of evolution, from fresh to scar structures.
Their
morphology and morphometric ratios are comparable to those of
terrestrial frost mounds. This study shows how the
paleolacustrine
environment of the Ma'adim Vallis/Gusev crater hydrogeologic
system may
have provided a suitable environment for the formation of frost
mounds.
Alternate hypotheses of formation including volcanism, fluvial
erosion,
and eolian erosion are discussed. Other features such as
heavings,
curvilinear troughs, hills, ridges, and depressions support the
idea of
a sediment/ice interaction. The typology of the mounds and
plausible
mechanisms for their formation are proposed. Their presence could
support the model of a massive water body in Gusev during the
Amazonian
and provide indicators of paleoenvironmental conditions at the
time
of their formation. (C) 2000 Academic Press.
===========
(8) ELLIPTICAL CRATERS ON MARS, VENUS AND MOON
W.F. Bottke*), S.G. Love, D. Tytell, T. Glotch: Interpreting the
elliptical crater populations on Mars, Venus, and the Moon.
ICARUS,
2000, Vol.145, No.1, pp.108-121
*) CORNELL UNIVERSITY,CTR RADIOPHYS & SPACE
RES,ITHACA,NY,14853
Asteroids or comets striking a planetary surface at very shallow
angles
produce elliptical-shaped craters. According to laboratory impact
experiments (D. E. Gault and J. A. Wedekind 1978, Proc. Lunar
Planet.
Sci. Conf. 9th, 3843-3875), elliptical craters result from impact
angles within similar to 5 degrees of horizontal and less than 1%
of
projectiles with isotropic impact trajectories create elliptical
craters. This result disagrees with survey results which suggest
that
approximately 5% of all kilometer-sized craters formed on Mars,
Venus, and the Moon have elliptical shapes. To explain this
discrepancy, we examined the threshold incidence angle necessary
to
produce elliptical craters in laboratory impact experiments.
Recent
experiments show that aluminum targets produce elongated craters
at
much steeper impact angles than sand targets. This suggests that
target
properties are as important as the projectile's impact angle in
determining the eventual ellipticity of the crater. Creating a
model
which interpolates between impact data produced using sand and
aluminum
targets, we derive a new elliptical crater threshold angle of 12
degrees from horizontal for Mars, Venus, and the Moon. This leads
to a
predicted proportion of elliptical craters that matches
observations
within uncertainty given a random projectile population. We
conclude
that the observed proportion of elliptical craters on these
bodies is a
natural by-product of projectiles striking at random angles, and
that
no additional formation mechanisms are needed. (C) 2000 Academic
Press.
==========
(9) MARE SOILS & CRATERS
M.I. Staid*) & C.M. Pieters: Integrated spectral analysis of
mare soils
and craters: Applications to eastern nearside basalts. ICARUS,
2000,
Vol.145, No.1, pp.122-139
*) BROWN UNIVERSITY,DEPT GEOL SCI,BOX 1846,PROVIDENCE,RI,02912
High spatial resolution Clementine images are examined to measure
the
reflectance properties of small and optically immature mare
craters
that have sampled discrete compositional units. The spectral
properties
of these relatively crystalline mare materials are compared to
associated mature soils to determine the effects of space
weathering on
specific basalt types. Space weathering is observed to alter the
optical properties of distinct lunar basalt units in a systematic
manner allowing compositional distinctions to be recognized
across
maturity states. Ultraviolet/visible reflectance properties of
mare
basalts are sensitive to titanium content but are relatively
independent of maturity state and demonstrate only a slight
reddening
as regoliths mature to soils. Other compositional distinctions
between
basalt types are identified by differences in albedo and band
strength
of ferrous minerals that are maintained over a full range of
maturity
states. Immature deposits within large craters are compared to
the
spectral properties of well-defined mare units to examine the
composition of buried materials. When craters excavate through
the
mare, highland contamination is readily identified as a mixing
relation
between mafic and feldspathic lithologies. The approach presented
here
provides new information on the composition and stratigraphy of
several
nearside mare deposits, including the identification of thin
low-iron
and very low titanium basalts in Lacus Somniorum and more
iron-rich
low-titanium basalts in eastern Mare Frigoris. (C) 2000 Academic
Press.
=========
(10) COLLISION RATES IN THE KUIPER BELT & CENTAUR REGIONS
D.D. Durda & S.A. Stern: Collision rates in the present-day
Kuiper Belt
and Centaur regions: Applications to surface activation and
modification on comets, Kuiper Belt objects, Centaurs, and
Pluto-Charon. ICARUS, 2000, Vol.145, No.1, pp.220-229
*) SW RES INST,SPACE STUDIES DEPT,1050 WALNUT ST,SUITE
426,BOULDER,CO,80302
We present results from our model of collision rates in the
present-day
Edgeworth-Kuiper Belt and Centaur region. We have updated
previous
results to allow for new estimates of the total disk population
in
order to examine surface activation and modification time scales
due to
cratering impacts. We extend previous results showing that the
surfaces
of Edgeworth-Kuiper Belt objects are not primordial and have been
moderately to heavily reworked by collisions. Objects smaller
than
about r = 2.5 km have collisional disruption lifetimes less than
3.5
Gyr in the present-day collisional environment and have probably
been
heavily damaged in their interiors by large collisions. In the
30- to
50-AU region, impacts of 1-km-radius comets onto individual
100-km-radius objects occur on 7 x 10(7)-4 x 10(8)-year time
scales,
cratering the surfaces of the larger objects with similar to 8-54
craters 6 km in diameter over a 3.5-Gyr period. Collision time
scales
for impacts of 4-m-radius projectiles onto 1-km-radius comets
range
from 3 x 10(7), to 5 x 107 years. The cumulative fraction of the
surface area of 1- and 100-km-radius objects cratered by
projectiles
with radii larger than 4 m ranges from a few to a few tens
percent over
3.5 Gyr. The flux of Edgeworth-Kuiper Belt projectiles onto Pluto
and
Charon is also calculated and is found to be similar to 3-5 times
that
of previous estimates, Our impact model is also applied to
Centaur
objects in the 5- to 30-AU region. We find that during their
dynamical
lifetimes within the Centaur region, objects undergo very little
collisional evolution. Therefore, the collisional/cratering
histories
of Centaurs are dominated by the time spent in the
Edgeworth-Kuiper
Belt rather than the time spent on planet-crossing orbits.
Further, we
find that the predominant surface activity of Centaur objects
like
Chiron is most likely not impact-induced. (C) 2000 Academic
Press.
==========
(11) MELT PRODUCTION IN OBLIQUE IMPACTS
E. Pierazzo*) & H.J. Melosh: Melt production in oblique
impacts.
ICARUS, 2000, Vol.145, No.1, pp.252-261
*) UNIVERSITY OF ARIZONA,LUNAR & PLANETARY LAB,1629 E UNIV
BLVD,TUCSON,AZ,85721
Hydrocode modeling is a fundamental tool for the study of melt
production in planetary impact events. Until recently, however,
numerical modeling of impacts for melt production studies has
been
limited to vertical impacts. We present the first results of the
investigation of melt production in oblique impacts. Simulations
were
carried out using Sandia's three-dimensional hydrocode CTH,
coupled to
the SESAME equation of state. While keeping other impact
parameters
constant, the calculations span impact angles (measured from the
surface) from 90 degrees (vertical impact) to 15 degrees. The
results
show that impact angle affects the strength and distribution of
the
shock wave generated in the impact. As a result, both the
isobaric core
and the regions of melting in the target appear asymmetric and
concentrated in the downrange, shallower portion of the target.
The use
of a pressure-decay power law (which describes pressure as
function of
linear distance from the impact point) to reconstruct the region
of
melting and vaporization is therefore complicated by the
asymmetry of
the shock wave. As an analog to the pressure decay versus
distance from
the impact point, we used a 'volumetric pressure decay,' where
the
pressure decay is modeled as a function of volume of target
material
shocked at or above the given shock pressure. We find that the
volumetric pressure decay exponent is almost constant for impact
angles
from 90 degrees to 30 degrees, dropping by about a factor of two
for a
15 degrees impact. In the range of shock pressures at which most
materials of geologic interest melt or begin to vaporize, we find
that
the volume of impact melt decreases by at most 20% for impacts
from 90
degrees down to 45 degrees. Below 45 degrees, however, the amount
of
melt in the target decreases rapidly with impact angle. Compared
to the
vertical case, the reduction in volume of melt is about 50% for
impacts
at 30 degrees and more than 90% for a 15 degrees impact. These
estimates do not include possible melting due to shear heating,
which
can contribute to the amount of melt production especially in
very
oblique impacts. Studies of melt production in vertical impacts
suggest
an energy scaling law in agreement with the point source limit.
An
energy scaling law, however, does not seem to hold for oblique
impacts,
even when the impact velocity is substituted by its vertical
component.
However, we find that for impact angles between about 30 degrees
and 90
degrees (a range that includes 75% of impact events on planetary
surfaces) the volume of melt is directly proportional to the
volume of
the transient crater generated by the impact. (C) 2000 Academic
Press.
===============
(12) AND FINALLY: APOCALYPTIC DESIRE FOR GREEN DICTATORSHIP &
GLOBAL MASS STARVATION
From National Post, 3 June 2000
http://www.nationalpost.com/financialpost.asp?f=000603/307314&s2=fpcomment&s3=fpeditorials
BOOK REVIEW
The renegade captain of spaceship Earth
Maurice Strong has risen from poverty to the top of the
international
'save the Earth' movement. But his recent book shows the fatal
flaws in
his ill-conceived new world order, writes Peter Foster
Peter Foster
Financial Post
For those "paranoid right wingers" who claim that
Maurice Strong is at
the centre of a plot of take over the world, his autobiography,
Where
on Earth are We Going?, contains both bad news and good news. The
bad
news: You weren't paranoid after all. The good news: Mr. Strong's
plan
for "Managing the World without World Government,"
while strategically
ingenious, is as unworkable as it is transparent.
The most startling chapter of Where in the World are We Going? is
the
first, a "Report to the Shareholders, Earth Inc.,"
dated Jan. 1, 2031.
In Maurice Strong's mental future, "The human tragedy is on
a scale
hitherto unimagined." There have been unprecedented extremes
of
weather. The North American prairies are experiencing their 10th
year
of drought. "[W]ater vendors with armed guards roam the
streets of Los
Angeles." Hundreds of thousands of people have just died in
Washington
from a heat wave. There are plagues of insects and rodents.
Malaria has
turned New Orleans into a "shrinking fortress held only with
poisonous
amounts of lethal pesticides."
In Mr. Strong's desire to compound future horrors (particularly
in the
United States), he has Florida both underwater and plotting to
secede.
Perhaps it's planning a political union with Atlantis. Meanwhile,
despite the environmental horrors of the U.S., illegal immigrants
are
still "stumbling over the polar ice caps" to reach it,
which certainly
makes a rusty Chinese freighter look good.
But not all is bleak. There's a good guy running Germany, a
"benevolent
dictator" seeking "to ensure that all Germans work
together for
the common good and share equitably in both the sacrifices and
the
benefits achieved." There are other "scattered islands
of sanity
and order" to be found. One such is Crestone, Colo.: "A
community
created as a spiritual retreat in recent materialistic times has
proven a haven for the virtues of sustainability, harmony and
ethical husbandry' " (Mr. Strong is too modest to mention
here
that he founded the community). There are other bright spots.
"Everywhere, indigenous people are rediscovering their
traditional
way of life" (disease and poverty?). Order is being restored
by
"volunteer security corps." Mmmm. Sounds like
non-governmental
organizations with guns. People have turned away from science and
toward religion. But the brightest spot lies in forecasts that
two-thirds of the world's already-diminished population may be
wiped out, "... a glimmer of hope for the future of our
species
and its potential for regeneration."
FULL BOOK REVIEW at
http://www.nationalpost.com/financialpost.asp?f=000603/307314&s2=fpcomment&s3=fpeditorials
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