PLEASE NOTE:
*
CCNet DIGEST, 4 December 1998
-----------------------------
Sherlock Holmes and Dr Watson went on a camping trip. After a
good meal and a bottle of wine they lay down for the night,
and went to sleep.
Some hours later, Holmes awoke and nudged his faithful
friend. "Watson, look up at the sky and tell me what you
see."
Watson replied, "I see millions and millions of stars."
"What does that tell you?" Holmes inquired.
Watson pondered for a minute. "Astronomically, it tells me
that there are millions of galaxies and potentially billions
of planets. Astrologically, I observe that Saturn is in Leo.
Horologically, I deduce that the time is approximately a
quarter past three. Theologically, I can see that God is all
powerful and that we are small and insignificant.
Meteorologically, I suspect that we will have a beautiful day
tomorrow. What does it tell you?"
Holmes was silent for a minute, then spoke. "Watson, you
idiot. Some bastard has stolen our tent."
------------------
(1) STILL NO IMPACT FRAGMENTS IN GREENLAND
David Morrison <dmorrison@arc.nasa.gov>
(2) THE PUBLIC AND THE IMPACT HAZARD
David Morrison <dmorrison@arc.nasa.gov>
(3) FURTHER PROGRESS IN THE LONEOS NEO SEARCH
Ted Bowell
(4) SCIENTISTS, NASA & US AIR FORCE IN JOINT LEONIDS RESEARCH
Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
(5) UK BASE 'IS STAR WARS STATION' - AND SAVED THOUSANDS OF LIVES
BBC ONLINE NETWORK
http://news.bbc.co.uk/hi/english/uk/newsid_227000/227599.stm
(6) EARTH MAY HAVE TILTED MORE MILLIONS OF YEARS AGO
Simon Mansfield <simon@spacer.com>
(7) LIQUID OCEANS BENEATH EUROPA'S FROZEN CRUST?
NASA Science News <expressnews@sslab.msfc.nasa.gov>
(8) THE 2/1 COMMENSURABILITY WITH JUPITER AND THE ORIGIN OF THE
RESONANT ASTEROIDS
M. Moons et al., FUNDP
(9) ACCRETION OF INTERPLANETARY DUST PARTICLES BY THE EARTH
S.J. Kortenkamp & S.F. Dermott, CARNEGIE
INST WASHINGTON
(10) SEASONAL CHANGES IN SPORADIC METEOR RATES
R.W. Schmude, GORDON COLLEGE
(11) DISTRIBUTION & EVOLUTION OF WATER ICE IN THE SOLAR
NEBULA
K.E. Cyr et al., UNIVERSITY OF ARIZONA
========================
(1) STILL NO IMPACT FRAGMENTS IN GREENLAND
From David Morrison <dmorrison@arc.nasa.gov>
As we approach the anniversary of the widely discussed Greenland
bolide of December 9, 1997, a news update is in order. You
may
recall that at the time, this very bright meteor created quite a
sensation with claims that it had produced a large crater and/or
deposited many meteorite fragments. Some even claimed that it was
"another Tunguska". Search expeditions were sent out,
but they
returned empty-handed. No impact crater or meteorites or other
physical evidence of an explosion has been recovered.
Perhaps this is a lesson that, while bright meteors are
spectacular
to see and may in a few cases (such as Peekskill) lead to the
fall of
meteorites, they are not hazardous. Except for the rare iron
meteorites, the limit for an incoming object to penetrate into
the
lower atmosphere or surface is about 5 megatons of kinetic
energy.
Thus low-altitude explosions are generally once-in-century
events,
and they are quite different from even a very bright meteor.
David Morrison
================================================================
(2) THE PUBLIC AND THE IMPACT HAZARD
From David Morrison <dmorrison@arc.nasa.gov>
We all recognize that over the past 5 years the idea of an impact
hazard has penetrated into general public consciousness.
This is
especially true in 1998, following the popular films Deep Impact
and
Armageddon.
One example that many of you in the United States saw was the
advertisement last summer for a sport-utility vehicle that read
simply "Rain, snow, asteroids . . . whatever".
Another example in today's news is a comment by US Representative
Ellen Tauscher who said that for her to change her mind about the
issue of impeachment of President Clinton "would take a
meteor to
hit".
=====================
(3) FURTHER PROGRESS IN THE LONEOS NEO SEARCH
From Ted Bowell
I am pleased to announce that, for the first time, we
successfully
ran the LONEOS system in an automatic mode on the nights of 5
November and 6 November UT. We took 292 images on the first night
and
296 images on the second, in all logging 17 hours of unattended
operation.
From LONEOS' inception, we have used the macro interpretation
facility of the camera control software to run the telescope and
camera. For automatic operation, we combined a sequence of
slightly
modified macros into a 'super' macro that could control the
telescope, camera, and data analysis computers for the entire
night.
Bruce Koehn opened the dome (hand-cranked!) and started the
supermacro at dusk, and then returned after dawn to examine the
automatically logged moving-object detections.
The nights we observed were the second and third night after full
Moon, so the sky was bright. We tried to stay at least 90 deg
from
the Moon, but that was not always possible. On the first night,
we
apparently had frost on the optics and detected only 16 asteroids
(one of them---1373 Cincinnati---at +71 deg declination). On the
second night, we found 94 asteroids before clouds came in. Of
these,
three were interesting enough to make it on to the Minor Planet
Center's confirmation list (all three have been reobserved, and
we'll
find out what kind of objects they are in the next day or two).
Clearly, when we observe in the automatic mode we won't be as
productive as when an observer is present because he/she can fix
a
variety of small problems, such as removing frost, retaking
imperfect
images, restarting crashed programs, etc.). But during the time
near
full Moon and at times when it is impossible to schedule an
observer,
this is a good way to gather data.
Ted Bowell (Nov 13, 1998)
======================================================
(4) SCIENTISTS, NASA & US AIR FORCE IN JOINT LEONIDS RESEARCH
From Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
Air Force News Service
Released: 2 Dec 1998
Scientists launch Leonid meteor shower missions from Kadena
By Staff Sgt. Orville Desjarlais, 18th Wing Public Affairs
KADENA AIR BASE, Japan (AFPN) -- Kadena became a part of
scientific
history recently when the 18th Wing assisted in the first
aircraft
mission to study the Leonid meteor showers over the skies of
Okinawa.
Scientists from around the world, including the Air Force
Research
Laboratory and NASA, boarded two modified aircraft Nov. 17 at
Kadena
and flew above nasty cloud cover to try and unlock the mysteries
of
the rarely observed Leonid meteor storm -- one such secret may
contain the answers to the origins of life itself.
Though rain ruined the viewing of the meteor showers from the
ground,
scientists climbed aboard a modified L-188C Electra aircraft from
the
National Center for Atmosphere Research and a U.S. Air Force
Flying
Infrared Signatures Technology Aircraft from Edwards Air Force
Base,
Calif., and got a clear view of the showers.
The Leonid meteors originate from the comet Tempel-Tuttle that
completes an orbit around the sun every 33 years, leaving a trail
of
dust and debris in its path. When the Earth crosses an especially
dense concentration of the comet trail, the result is the Leonid
meteor storm -- "shooting stars" streaking through
Earth's upper
atmosphere sometimes at rates as high as thousands per hour.
This year, Earth was expected to pass a region just behind the
comet
and outside its orbit. Scientists predicted the best place to
view
the storm was from Japan.
However, the Leonid meteor showers couldn't live up to the
anticipation and hoopla it had created since its last appearance
in
1966. Prior to the meteor storm, researchers expected anywhere
from
200 to 10,000 meteor sightings an hour. What they saw was between
200-300 meteors an hour, according to Peter Jenniskens, an
astronomer
and principal investigator at the Search for Extraterrestrial
Intelligence Institute, Mountain View, Calif.
"The Leonids shower is your best chance to see a meteor
shower in
your lifetime. After 1999, it won't return for the next 100
years,"
Jenniskens said.
"We had the best showers I've ever witnessed. We actually
came to
within about a mile and a half of a meteor trail, " said
Jenniskens
after the nine-hour flight.
The mix of astronomers, atmospheric physicists and meteor
specialists
will now analyze all the data they collected using
high-resolution,
stereoscopic images and spectrographic observations of meteor
dynamics and chemistry to study the origin, evolution and destiny
of
life in the universe, according to Jenniskens.
Scientists will search for organic material in meteoroids to
determine what comets are made of and how they interact with the
atmosphere. This may provide important clues about how life began
on
Earth and whether extraterrestrial material, brought here by
comets,
triggered that process, according to NASA officials.
Scientists also looked for clues about how biogenic compounds
formed
in stars are eventually incorporated into planets.
Helping count meteoroids during the mission was pilot Capt. Kris
Thompson, task force commander for FISTA, who was involved in the
program for the past six months. Meteor showers peaked the
interest
of Air Force officials because of the possible damage meteors
could
cause to the estimated 500 satellites circling the globe.
"They wanted us to look out the window quite a bit and count
the
meteors ourselves to give (scientists) an inkling as too the
meteor
rate in our field of vision up front," said Thompson, 452nd
Flight
Test Squadron. Because of the demands of flying the aircraft and
counting meteoroids simultaneously, three pilots rotated in and
out
of the pilot seat.
The Kadena team provided support to the scientists as they geared
up
for the flight three days prior to the mission.
Help came in the way of fixing broken parts on the aircraft, such
as
having to build from scratch two metal tubes for a hydraulic
reservoir and a piece of metal that acted as an exhaust cover,
and
finding a starter control valve. The 82nd Reconnaissance Squadron
maintenance section and 18th Operations Support Squadron solved
most
of the scientists' problems, but the rest of the base assisted in
providing everything from transportation, to food and lodging.
Scientists are predicting another storm in 1999, but there is
some
speculation as to where the best viewing site will be. Some say
over
the night sky of Europe, while others say the best viewing will
be
over the continental United States.
=====================
(5) UK BASE 'IS STAR WARS STATION' - AND SAVED THOUSANDS OF LIVES
From the BBC ONLINE NETWORK
http://news.bbc.co.uk/hi/english/uk/newsid_227000/227599.stm
The base is one of the UK's most secretive sites
A United States satellite station in northern England is being
used for
a 'Star Wars' weapons system, a BBC documentary has alleged.
The BBC's Close Up North highlighted the work at controversial
RAF
Menwith Hill, near Harrogate, North Yorkshire, claiming
facilities at
the station, which is leased to the US National Security Agency,
now
include the Space Based Infra Red System (SBIRS).
The term Star Wars was first applied to defence systems during
Ronald
Reagan's time as US president.
Documentary producer Ian Cundall said of RAF Menwith: "The
idea is that
they will detect missiles even before they are launched, they
will be
spotted when the engines are lit. It will in turn relay
information to
laser satellites in space which will destroy the missiles."
The lasers will also be able to destroy other satellites thereby
"blinding the enemy", according to Mr Cundall.
A Ministry of Defence spokesman said: "The system at Menwith
Hill is a
defence system used in a passive way. Any thoughts that there are
laser-based space systems is pure fantasy."
On the programme Rear Admiral Eugene Carroll, of the
Washington-based
Centre for Defence Information, said the system is illegal under
a
number of international treaties, not least the 1972
Anti-Ballistic
Missile Treaty.
'Base saved lives'
A team of BBC graphic artists claim they have drawn up the first
3D
image of the interior of the site huge 'golf ball' buildings.
Mr Cundall said: "For the first time we are going to give
people an
inside view of what is Britain's most secretive building."
The programme also said the base saved thousands of lives during
the
Gulf War. Former US Air Force General Charles Horner said the
base was
able to detect scud missiles, meaning they could be destroyed
before
they reached their target.
Copyright 1998, BBC
========================
(6) EARTH MAY HAVE TILTED MORE MILLIONS OF YEARS AGO
From Simon Mansfield <simon@spacer.com>
Research: Earth may have tilted more millions of years ago
The Earth might have tilted toward the sun 600 million years ago
far more than it does today, making the polar regions warm and
the
tropics cold, according to research published today in the
journal
Nature. [http://www.flatoday.com/space/today/120398g.htm]
Old story, but they claim a new theory
Simon Mansfield
Free Private Email - Space Domains http://www.spacer.com/signup.html
Daily Space News -- http://www.spacer.com
==========================
(7) LIQUID OCEANS BENEATH EUROPA'S FROZEN CRUST?
From NASA Science News <expressnews@sslab.msfc.nasa.gov>
December 3 1998 -- The frosty plains of Europa
Evidence continues to mount for liquid oceans beneath Europa's
frozen
crust. As the Galileo spacecraft returns new images of this
intriguing moon, scientists are studying ice samples from a
potentially similar environment here on Earth.
FULL STORY: http://science.nasa.gov/newhome/headlines/ast03dec98_1.htm
=====================
(8) THE 2/1 COMMENSURABILITY WITH JUPITER AND THE ORIGIN OF THE
RESONANT ASTEROIDS
M. Moons*), A. Morbidelli, F. Migliorini: Dynamical structure of
the
2/1 commensurability with Jupiter and the origin of the resonant
asteroids. ICARUS, 1998, Vol.135, No.2, pp.458-468
*) FUNDP, DEPT MATH, 8 REMPART VIERGE, B-5000 NAMUR, BELGIUM
Using a semi-analytic approach, we provide a three-dimensional
picture
of the secular dynamics in the 2/1 mean-motion commensurability,
mapping the most chaotic regions and the two islands of
quasi-regular
motion. Five asteroids have recently been discovered in one of
these
islands and it has been conjectured that they were injected by
the
Themis-family formation event, which occurred close to the 2/1
resonance border. We show that this scenario is viable from the
orbital
and size distribution point of view and that it would also
explain why
no asteroids have been observed in the second island. Finally we
discuss the possibility that the 2/1 resonance is the dominating
source
of CI and CM meteorites, as was suggested on spectro-scopical
bases. We
find that the efficiency of the 2/1 resonance is far too small
for it
to be such a dominating source. (C) 1998 Academic Press.
=====================
(9) ACCRETION OF INTERPLANETARY DUST PARTICLES BY THE EARTH
S.J. Kortenkamp & S.F. Dermott: Accretion of interplanetary
dust
particles by the Earth. ICARUS, 1998, Vol.135, No.2, pp.469-495
*) CARNEGIE INST WASHINGTON,DEPT TERR MAGNETISM,5241 BROAD BRANCH
RD NW,WASHINGTON,DC,20015
Analyses of hypervelocity micrometeoroid impact craters preserved
in
lunar material and on the panels of the Long Duration Exposure
Facility
(LDEF) indicate that each year Earth accretes about 3 x 10(7) kg
of
interplanetary dust particles (IDPs) from the zodiacal cloud (E.
Grun
et al. 1985, Astron. Astrophys. 286, 915-924; S. G. Love and D.
E.
Brownlee, 1993, Science 262, 550-553). The size distributions of
these
lunar and LDEF craters indicate that the mass distribution of
IDPs
encountering Earth peaks at about 200 mu m diameter. This
particle-size
cutoff may be indicative of collisionally evolved asteroidal
dust,
where the collisional lifetime of dust particles larger than
similar to
100 mu m is shorter than the time required for their orbits to
decay
under Poynting-Robertson light drag from the asteroid belt to
Earth (B.
Angstrom. S. Gustafson, 1994, Annu. Rev. Earth Planet. Sci. 22,
553-595). Additionally, analyses of IDPs collected from the
stratosphere by high-flying aircraft reveal a diversity in
chemical
composition which is even narrower than that of the meteorites
(G. J.
Flynn, 1995, Nature 376, 114). Together these findings suggest
that
IDPs present in the atmosphere and our collections may originate
from
very limited sources in the asteroid belt. The most abundant
sources of
dust to be unambiguously linked to the zodiacal cloud are the
three
asteroid families Eos, Themis, and Koronis-the progenitors of the
ten-degree and low-latitude dust bands discovered by the Infrared
Astronomical Satellite in 1984. We use direct numerical
integration of
the full equations of motion to model the orbital evolution of
dust
particles from these three families as well as from other
nonfamily
asteroids and from the population of known short period comets.
Our
simulations include gravitational perturbations from the planets,
radiation pressure, and solar wind drag. We find that a large,
and
perhaps the dominant, fraction of the IDPs accreted by Earth
comes from
the asteroid families Eos, Themis, and Koronis and that probably
fewer
than 25% of accreted IDPs come from comets. We also find a
seasonal
variation in the distribution of ascending nodes of the Themis
and
Koronis dust particle orbits near Earth. Earth-orbiting
instruments
utilizing aero-gels could exploit these seasonal variations to
collect
and return intact samples of these two asteroid families.
Finally, we
demonstrate how the long-term accretion rate of asteroidal dust
from
all sources should be anti-correlated with Earth's changing
orbital
eccentricity. (C) 1998 Academic Press.
==================
(10) SEASONAL CHANGES IN SPORADIC METEOR RATES
R.W. Schmude: Seasonal changes in sporadic meteor rates. ICARUS,
1998,
Vol.135, No.2, pp.496-500
GORDON COLLEGE, 419 COLL DR,BARNESVILLE,GA,30204
R. Lunsford and G. Zay observed 15,114 sporadic meteors between
1992
and 1996 and their data are analyzed in this report. The data
reveal a
distinct seasonal trend with rates from July through December
being
1.31 +/- 0.10 times those from January through June. After the
effect
of the changing direction of the apex of Earth's way is removed,
it is
found that the July through December rates are 3 +/- 10% higher
than
those from January through June. The average corrected hourly
rate for
sporadic meteors between 1992 and 1996 is 10.7 +/- 1.3 at 2:00 AM
local
standard time under a limiting magnitude of 6.5, which is
consistent
with observations made between 1981 and 1991. (C) 1998 Academic
Press.
==================
(11) DISTRIBUTION & EVOLUTION OF WATER ICE IN THE SOLAR
NEBULA
K.E. Cyr*), W.D. Sears, J.I. Lunine: Distribution and evolution
of
water ice in the solar nebula: Implications for Solar System body
formation. ICARUS, 1998, Vol.135, No.2, pp.537-548
*) UNIVERSITY OF ARIZONA, DEPT PLANETARY SCI, LUNAR &
PLANETARY
LAB, 1629 E
Water is important in the solar nebula both because it is
extremely
abundant and because it condenses out at 5 AU, allowing all three
phases of H2O to play a role in the composition and evolution of
the
Solar System. In this paper, we undertake a thorough examination
of and
model the inward radial drift of ice particles from 5 AU. We then
link
the drift results to the outward diffusion of vapor, in one
overall
model based on the two-dimensional diffusion equation, and
numerically
evolve the global model over the lifetime of the nebula. We find
that
while the inner nebula is generally depleted in water vapor,
there is a
zone in which the vapor is enhanced by 20-100%, depending on the
choice
of ice grain growth mechanisms and rates. This enhancement peaks
in the
region from 0.1 to 2 AU and gradually drops off out to 5 AU.
Since this
result is somewhat sensitive to the choice of nebular temperature
profile, we examine representative hot (early) and cool (later)
conditions during the quiescent phase of nebular evolution.
Variations
in the pattern of vapor depletion and enhancement due to the
differing
temperature profiles vary only slightly from that given above.
Such a
pattern of vapor enhancement and depletion in the nebula is
consistent
with the observed radial dependence of water of hydration bands
in
asteroid spectra and the general trend of asteroid surface
darkening.
This pattern of water vapor abundance will also cause variations
in the
C:O ratio, shifting the ratio more in favor of C in zones of
relative
depletion, affecting local and perhaps even global nebular
chemistry,
the latter through quenching and radial mixing processes. (C)
1998
Academic Press.
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