PLEASE NOTE:
*
CCNet DIGEST, 5 March 1999
--------------------------
QUOTE OF THE DAY
"We do need a number of telescopes
at different longitudes and
different latitudes in order to have a
complete survey. You can
think of it this way: If an asteroid
should come by while one side
of the earth is facing it, we want to
have a telescope that can
see it. (It is a) very good idea (to set
up telescopes in the
Southern Hemisphere, especially
Australia). Should an asteroid
pass in an extreme southerly direction,
we could easily miss that
one" (Paul Chodas, JPL, 3 March
1999)
(1) COOKING UP A NEAR-EARTH ASTEROID
INSCiGHT, Academic Press.
http://www.academicpress.com/inscight/03041999/grapha.htm
(2) A CALL TO MONITOR KILLER ASTEROIDS
MSNBC
http://www.msnbc.com/news/spacenews_front.asp
(3) RESEARCHERS UNCOVER REVOLUTIONARY NEW PHYSICS DISCOVERY
Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
(4) DESPERATELY SEEKING PSYCHE FAMILY
D.R. Davis*), P. Farinella, F. Marzari,
PLANETARY SCI INST SJI
(5) SOILS FOR SPACE-BASED AGRICULTURE
M.N. Mautner, LINCOLN UNIVERSITY
(6) ASTEROID ROTATION STATS
J.R. Donnison*) & M.P. Wiper, UNIVERSITY
OF LONDON
=======================
(1) COOKING UP A NEAR-EARTH ASTEROID
From INSCiGHT, Academic Press.
http://www.academicpress.com/inscight/03041999/grapha.htm
Thursday, 4 March 1999, 5 pm PST
Cooking Up a Near-Earth Asteroid
By Mark Sincell
Take two of the many asteroids orbiting between Mars and Jupiter.
Smash
them together into fairly small pieces. Then add sunlight. This
is the
new recipe, proposed in tomorrow's Science, for the surprisingly
large
numbers of asteroids that pass by Earth every year.
Scientists generally agree that gravitational tugs from Mars,
Jupiter,
and Saturn can yank asteroids out of the main belt and into
near-Earth
orbits. But for this to happen, an asteroid must encounter a
resonance,
which is like an eddy of chaotic gravitational fields that
bounces
asteroids out of their old orbits. The resonances that create
near-Earth asteroids are found along the orbit of Mars, but there
aren't enough to explain all the observed near-Earth asteroids,
says
Paolo Farinella, an astrophysicist at the Universita di Trieste
in
Italy. Now Farinella and his colleague D. Vokrouhlicky, a space
scientist at Charles University in Prague, Czech Republic,
suggest that
the Yarkovsky effect -- a little known process first studied over
100
years ago by a Russian engineer -- may solve this long-standing
conundrum by funneling more asteroids into the known resonances.
Here's the idea. As the sun shines on an asteroid, it warms the
surface
-- except for crevices and other shaded parts of the surface. The
hotter regions of the surface then push on the asteroid by
radiating
infrared light. Theoretical models suggest that these tiny forces
can
gradually shift the asteroid's orbit, and, if the calculations
are
correct, this wandering ups the odds of the asteroid crossing
Mars's
orbit and falling into a resonance. The Yarkovsky effect works
most
efficiently on objects smaller than 20 kilometers, so Farinella
has
proposed that the Yarkovsky effect causes the rubble of large
asteroids
to drift into resonances, which kick some of the smaller pieces
into
near-Earth orbits.
"Farinella's work is an important advance," says Andrew
Cheng, an
astronomer at the Applied Physics Laboratory in Laurel, Maryland,
"but
we are still very far from a complete understanding" of the
processes
that create near-Earth asteroids. Cheng cautions that while the
Yarkovsky effect may work in concert with collisions and gravity
to
bring asteroids into near-Earth orbits, no one has found hard
evidence
to support the theory that the main belt spawns near-Earth
asteroids.
(c) 1999 The American Association for the Advancement of Science
===================
(2) A CALL TO MONITOR KILLER ASTEROIDS
From MSNBC
http://www.msnbc.com/news/spacenews_front.asp
British MP urges government to take lead role in a global effort
MSNBC STAFF AND WIRE REPORTS
LONDON, March 3 — A member of Britain’s
Parliament is launching a
campaign for closer monitoring of massive asteroids that could
kill
billions of people if they crashed into the Earth.
"AT PRESENT an asteroid could hit the Earth and we would
have about 20
seconds’ notice," Lembit Opik, a member of the minority
Liberal
Democrats, told a news conference Wednesday. "It isn’t
long enough to
say the Lord’s Prayer."
Opik’s Lithuanian grandfather, an astronomer, had an
asteroid named
after him.
Opik is urging the British government to set up an
asteroid-tracking
telescope, based in either Namibia or Australia. NASA’s 1992
Spaceguard
Survey Report recommended establishing six such dedicated
telescopes
around the globe to identify and track the 2,000 or so near-Earth
asteroids, minor planets measuring more than a kilometer (0.6
mile)
across that come close to Earth’s orbit.
Closer monitoring of asteroids would give scientists better data
to
calculate the course of near-Earth objects. For example, almost
exactly
a year ago, astronomers issued an alert warning that an asteroid
known
as 1997 XF11 might hit Earth in 2028 — but additional data
led to the
conclusion that the object would just miss our planet.
If an asteroid were ever found to be on a collision course with
Earth,
scientists hope to have enough lead time to figure out a way to
deflect
its course.
SCIENCE FICTION AND FACT
Asteroid interception is still the stuff of science-fiction
movies like
"Armageddon" or "Deep Impact," but Paul
Chodas, an astronomer at NASA’s
Jet Propulsion Laboratory, said the need for a bigger
asteroid-monitoring network was a scientific fact.
"We do need a number of telescopes at different longitudes
and
different latitudes in order to have a complete survey," he
told MSNBC.
"You can think of it this way: If an asteroid should come by
while one
side of the earth is facing it, we want to have a telescope that
can
see it."
Last year NASA announced that it would step up its efforts to
track
near-Earth objects. Chodas noted that there were already several
monitoring systems in the United States, one in Europe and one
under
development in Japan.
He said it was a "very good idea" to set up telescopes
in the Southern
Hemisphere, especially Australia. "Should (an asteroid) pass
in an
extreme southerly direction, we could easily miss that one,"
he said.
POTENTIAL DISASTER
Astronomer Mark Bailey, director of Northern Ireland’s
Armagh
Observatory, said a large asteroid hitting Earth would cause
disaster
on a scale comparable with the one which scientists believe wiped
out
the dinosaurs 65 million years ago. It doesn’t matter where
on Earth it
hits. The dust thrown into the atmosphere would cool the earth
drastically and cause a temporary shutdown of agriculture,"
he said.
"It could mean the loss of about a quarter of the world’s
population."
A globally threatening impact is likely to occur only once in
100,000
years. But because of the mass destruction such an impact would
cause,
the risk of any given citizen of the United States dying because
of an
asteroid impact has been estimated at 20,000 to one, Bailey said.
Jonathan Tate, director of the lobbying group Spaceguard UK, said
setting up the proposed telescope, thus encouraging other
developed
countries to take similar steps, would cost about $15 million
over 10
years.
"It is only sense to do something about this," Tate
said. "If the
Americans could get to the moon in 10 years, we can solve this
problem
in less than 10 years."
MSNBC’s Alan Boyle and Reuters contributed to this story.
Copyright 1999, MSNBC
=================
(3) RESEARCHERS UNCOVER REVOLUTIONARY NEW PHYSICS DISCOVERY
From Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
Clemson University
Clemson, South Carolina
CONTACTS:
Donald Clayton, (864) 656-5299, (864) 656-0805 (fax)
Weihong Liu, (423) 574-4707
Alexander Dalgarno, (617) 495-4403
WRITER: Sandy Dees, (864) 656-4193
2-25-99
RESEARCHERS UNCOVER REVOLUTIONARY NEW PHYSICS DISCOVERY
Clemson teams with Oak Ridge National Laboratory and Harvard
CLEMSON -- Astrophysicists at Clemson University, Oak Ridge
National
Laboratory and Harvard University discovered a new chemical
sequence
during research into how large carbon molecules might form in
exploding
stars known as supernovae.
The finding is casting doubt on the long-held chemical
equilibrium
theory and clearing the way for a new field -- kinetic chemistry.
"We believe we have uncovered new truths of chemistry,"
said Clemson's
Donald Clayton, an internationally known theoretical
astrophysicist.
"Some controversial aspects of supernovae, including
information about
their core or the amount of radioactivity they generate, can be
better
evaluated with this kinetic chemical theory." The research
team
included Clayton, ORNL's Weihong Liu and Harvard's Alexander
Dalgarno.
Their work, to be published in the Feb. 26 issue of
"Science," has
far-reaching implications for physics, chemistry, astronomy,
meteoritic
and planetary sciences. "Science" is the weekly journal
of the American
Association for the Advancement of Science.
Scientists had previously believed it impossible to convert
cosmic
carbon from a hot gas into a solid if there was more oxygen than
carbon
present. Conventional theory held that any free carbon atoms in
the
supernova gas should have reacted with the more abundant oxygen
atoms
to form carbon monoxide.
But the researchers discovered that supernova radioactivity
breaks the
strong chemical bond that holds carbon and oxygen together.
Energetic
electrons and ions allow carbon atoms to escape the pairing
mechanism,
leaving plenty of atomic carbon that can condense into solid
particles
and eventually be ejected from the supernova.
The breakthrough that led to the research are tiny grains of
"star
dust" found inside meteorites that fell to earth about a
million years
ago.
"These supernova graphite particles are the oldest material
fossils
that humankind can study, older than our solar system, at least
twice
as old as the oldest rocks on Earth and also twice as old as the
earliest biological fossil algae found on Earth," said
Clayton, who
first predicted the clues that would identify the starry fossils.
END
Order Information:
ARTICLE #6: "Condensation of Carbon in Radioactive Supernova
Gas" by D.
D. Clayton at Clemson University in Clemson, SC; W. Liu at Oak
Ridge
National Laboratory in Oak Ridge, TN and at U. of Tennessee in
Knoxville, TN; A. Dalgarno at Harvard-Smithsonian Center for
Astrophysics in Cambridge, MA.
IMAGE CAPTION: [http://clemsonews.clemson.edu/pix/claytonweb.GIF]
Clemson astrophysicist Donald Clayton and research colleagues
believe
they have uncovered "new truths of chemistry."
=========================
(4) DESPERATELY SEEKING PSYCHE FAMILY
D.R. Davis*), P. Farinella, F. Marzari: The missing Psyche
family:
Collisionally eroded or never formed? ICARUS, 1999, Vol.137,
No.1,
pp.140-151
*) PLANETARY SCI INST SJI,620 N 6TH AVE,TUCSON,AZ,85705
Asteroid 16 Psyche, the largest M-type asteroid, is widely
considered
to be the collisionally exposed core of an similar to 500-km
diameter
differentiated parent body which was similar to asteroid 4 Vesta.
However there is no dynamical family associated with Psyche nor
are
there spectroscopic data for the existence of the mantle or
crustal
material from the parent body. The usual explanation for the
missing
material requires that the Psyche parent body was collisionally
disrupted early in solar system history, followed by collisional
grinding of the family down to below the current observational
limit
sizes. We test the exposed core hypothesis for the origin of
Psyche
using a numerical code that simultaneously calculates both the
collisional evolution of the asteroid belt and the model family
formed by the breakup of the Psyche parent body (PPB). We find
that it
would take a projectile about 300-350 km in size to thoroughly
disrupt
a 500-km asteroid (the estimated size of the PPB), and that the
probability of such an event occurring in the first 500 Ma of
solar
system history is only about 1%. While the Psyche model family is
found
to have been significantly ground down subsequent to its
formation,
there should be several tens of survivors from the mantle and
crust
larger than similar to 10 km that should be spectroscopically
detectable by current technology. Although only a small fraction
of the
asteroids larger than 10 km have been discovered and observed
spectroscopically to date, none have been identified as potential
survivors from the PPB (Burbine et al. 1996, Meteor: Planet. Sci.
31,
607-620). Given the low probability of the disruption of a
Vesta-like
body and the lack of either dynamical or observational
confirmation of
a family or material from the parent body, we think it more
likely that
Psyche has possibly been shattered by impacts but not
catastrophically
disrupted. In this case, it would be a plausible candidate parent
body
for the mesosiderites. The exposed-core scenario more probably
applies
to other, smaller (diameter less than or similar to 100 km)
M-type
asteroids, which could be the parent bodies of the iron
meteorites.
However, this interpretation raises the interesting problem of
why
among the larger asteroids only Vesta and the PPB would have been
fully
differentiated. (C) 1999 Academic Press.
===============
(5) SOILS FOR SPACE-BASED AGRICULTURE
M.N. Mautner: Formation, chemistry and fertility of
extraterrestrial
soils: Cohesion, water adsorption and surface area of
carbonaceous
chondrite. Prebiotic and space resource applications. ICARUS,
1999,
Vol.137, No.1, pp.178-195
*) LINCOLN UNIVERSITY,DIV SOIL PLANT & ECOL SCI,LINCOLN,NEW
ZEALAND
Following microbial and plant responses to Murchison CM2
meteorite
nutrients, further soil fertility parameters are examined.
Cohesion of
the matrix is tested by dissolving in acidic disaggregation
agents, 0.4
M CH3COOH, 10% HNO3, H2SO4 (pH 3), 50%H2O2 + H2SO4 (pH 3), and
saturated CO2 solution. The responses suggest that carbonates and
the
organic polymer contribute as cementing agents, and that enhanced
disaggregation by H2O2 and diminished disaggregation in saturated
CO2
solutions may contribute to the weathering of carbonaceous
meteorites
in martian or early Earth environments, respectively. The cation
exchange capacities (CEC) of the solid (7.2 +/- 0.8 meq/100 g)
and
powdered Murchison (7.8 +/- 1.5 meq/100 g) are comparable. The
cation
exchange capacity is not reduced by oxidation or acetylation,
suggesting that the binding sites of exchangeable cations are
mostly
inorganic. The CEC correlates with water vapor adsorption similar
to
that for terrestrial soils. For example, at 20 degrees C and
P(H2O) =
10.8 mbars, 17 mg/g H2O is adsorbed on Murchison (CEC = 7.2
meq/100 g)
and only 0.6 mg/g on Allende (CEC = 0.4 meq/100 g). Under these
conditions 13 H2O molecules are adsorbed per surface cation in
Murchison and 8 H2O molecules/cation in Allende, similar to 9 H2O
molecules/cation in terrestrial soils and in montmorillonite.
Adsorption isotherms on the Murchison are convex at low
pressures,
indicating strong bonding of the first water molecules, and
concave at
high pressures, indicating a broad pore size distribution.
Isotherms at
278, 293, and 311 K yield isosteric heat of adsorption of 56.5
+/-
2.5 kJ/mol at 4-8 H2Oadsorbed molecules/cation, similar to that
for
montmorillonite. The isotherms yield a specific surface area of
S-w =
37 x 10(3) m(2)/kg for Murchison, larger than the 19 x 10(3)
m(2)/kg of
pure serpentine, suggesting contributions, in addition to the
main
serpentine-like phyllosilicates, by components equivalent to a
9-12%
smectic clay-like content. Water evaporation curves from
meteorite
surfaces display the multistage behavior typical of soils, with
slow rates for the evaporation of surface-adsorbed water. The gas
adsorption data allow an assessment of gas-adsorbed water
equilibrium
in the solar nebula and suggest possible self-catalytic effects
in
adsorption/aqueous alteration processes. The observed fertility
indicators and biological effects support the potential of
carbonaceous
chondrites to support early biological processes and as soils for
space-based agriculture. (C) 1999 Academic Press.
============================
(6) ASTEROID ROTATION STATS
J.R. Donnison*) & M.P. Wiper: Bayesian statistical analysis
of asteroid
rotation rates. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL
SOCIETY,
1999, Vol.302, No.1, pp.75-80
*) UNIVERSITY OF LONDON GOLDSMITHS COLL,DEPT MATH & COMP
SCI,NEW
CROSS,LONDON SE14 6NW,ENGLAND
Asteroid rotation rates have been analysed by many authors in the
past,
and one or more Maxwellian distributions have been fitted for
various
diameter ranges and taxonomic classes. The statistical results
and
physical interpretations of the models have varied widely. In
this new
approach we use Bayesian statistics to determine the separation
of the
larger asteroids, which are fitted with a single Maxwellian
distribution, from the smaller asteroids, which are fitted by a
mixture
of Maxwellian distributions. It is found that the optimal
separation
occurs at about 32.5 km, and that a mixture of three Maxwellians
comprising slow rotators, fast rotators and a population
identical to
the larger asteroids provides the best fit. Copyright 1999,
Institute
for Scientific Information Inc.
----------------------------------------
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*
LETTERS TO THE MODERATOR, 5 March 1999
--------------------------------------
MODERATOR'S NOTE: I am sorry for yesterday's problems with the
new
CCNet-ESSAY list. When I set up the new lists, I simply forgot to
inform my university's listserver that they should be *closed*
rather
than a free-for-all. The format has now been changed so that all
CCNet
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please
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Benny J Peiser
(1) SOME CORRECTIONS
Paolo Farinella <paolof@keplero.dm.unipi.it>
>
(2) IMPORTANT NEWS FROM AUSTRALIA
Gerrit Verschuur <GVERSCHR@MOCHA.MEMPHIS.EDU>
(3) MUSIC STARS
Scott Manley <spm@star.arm.ac.uk>
=================
(1) SOME CORRECTIONS
From Paolo Farinella <paolof@keplero.dm.unipi.it>
>
Dear Benny,
concerning the March 4 CCNet letters, I will probably be not
alone in
remarking that Chairman Sensenbrenner of the Committe on Science
of the
U.S. House of Representative is mixing up the major mass
extinctions.
The Permo-Triassic one, that he mentions in relation to the
dinosaurs'
demise, actually occurred some 150 Myr before that event. I also
don't
agree - but this is just an opinion - with the characterization
of the
proposed Clementine 2 mission as anti-NEO defense technology.
Some different errors are contained in Bob Kobres's letter on
Opik and
the EK-belt objects. I think Bob is aware of the fact that the
13-Myr
average interval found by Levison & Duncan for impact on
Earth by
comets from the EK belt is just an average, and does not imply in
any
way a periodicity. However, some readers may have misunderstood
this
crucial point. Also, the vast majority of these comets would be
km-sized objects, not much larger (Chiron-sized) bodies like
those
which are being discovered today in the belt. Finally, the
EK-generated
(short-period) comets have been probably formed beyond Neptune,
well
outside the Oort cloud comets which are mostly former
planetesimals
from the Jupiter zone, ejected after close planetary encounters.
Little is known on the density and composition of both types of
comets,
but the argument from the formation site works in reverse.
Best regards,
Paolo Farinella
================
(2) IMPORTANT NEWS FROM AUSTRALIA
From Gerrit Verschuur <GVERSCHR@MOCHA.MEMPHIS.EDU>
FROM A PRESS RELEASE FROM THE ANGLO-AUSTRALIAN OBSERVATORY, IN
EPPING,
NEW SOUTH WALES
(A few highlights shown to make a point.)
Southern Cosmic Census creates the largest map of the universe
Astronomers have created the largest map of the Universe using
the
Anglo-Australian Telescope, in NSW, Australia and there is much
more to
come. The scientists are using the 2dF (Two-degree field)
instrument on
the 3.9-metre Anglo-Australian Telescope (the largest optical
telescope
in Australia). Researchers are only part way through their work,
and
are planning to make the map 10 times as big.
.....
"We have been planning this survey for almost ten years, and
as the
results come flooding in our ambitious goals are being fulfilled.
At
this rate, we will have no problems completing our survey by
2001."
........
So far the 2dF Galaxy Redshift Survey has pinpointed 30 000
galaxies.
......
The 2dF is one of the most complex astronomical instruments ever
constructed. It took seven years to perfect, and was built
in-house at
the Anglo-Australian Observatory.........
COMMENT BY GERRIT VERSCHUUR
While making a map of the universe is a laudable task, I find it
ironic
that in Australia they are carrying out such a massive project
given
what happened to their asteroid search program.
The good news is that when the survey is complete we will know
which
galaxies pose a hazard to us!
========================
(3) MUSIC STARS
From Scott Manley <spm@star.arm.ac.uk>
Benny,
I don't know if anyone's mentioned it to you but there's a nice 2
page
article in the current issue of 'Q' magazine which lists all the
asteroids named after famous musicians. They interviewed Gareth
Williams and have a nice big picture showing the solar system...
except
that even if the asteroids are in the right place then Jupiter,
Venus
and Earth are in the wrong place....
And... in my continual quest to keep people interested in my NEO
map -
I've now added an AVI movie to the same page showing a year in
the life
of the earth as it flies through its 'Cosmic Shooting Gallery' -
look
at http://szyzyg.arm.ac.uk/~spm/neo_map.html
Scott Manley (aka Szyzyg)
-----------------
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