PLEASE NOTE:
*
CCNet DIGEST, 27 May 1999
-------------------------
Many congratulations on the 'Treble' to all ManU supporters on
CCNet!
---------------------------------------------------------------------
QUOTE OF THE DAY
"A worldwide research program has
come up with astonishing
evidence that humans have come so close
to extinction in the past
that it’s surprising we’re
here at all" (Lee Dyw, ABC News,
25 May 1999)
(1) POSSIBILITY OF IMPACT IN 2044 & 2046 STILL VERY SMALL,
BUT ASTEROID 1999 AN10 NEEDS TO BE CAREFULLY
MONITORED
Ron Baalke <baalke@ssd.jpl.nasa.gov>
(2) SPACEGUARD UK: QUESTION IN THE HOUSE OF LORDS
Jonathan TATE <fr77@dial.pipex.com>
(3) HOMO SAPIENS CAME CLOSE TO EXTINCTION - SEVERAL TIMES
ABC News Online, 26 May 1999
(4) 'LOST CONTINENT' DISCOVERED
BBC Online Network, Thursday, May 27, 1999
(5) DON'T FALL FOR THIS MISERABLE SERMON: US EVANGELIST PREACHES
APOCALYPTIC MESSAGE OF NEO-FATALISM
CNN, 25 May 1999
(6) ON THE DYNAMICAL EVOLUTION OF ATENS AND APOLLO ASTEROIDS
R. Dvorak & E. Pilat Lohinger, UNIVERSITY
OF VIENNA
(7) THE DIAMETER DISTRIBUTION OF EARTH-CROSSING ASTEROIDS
A. Poveda et al., UNIV NACL AUTONOMA MEXICO
(8) COLLISIONAL EVOLUTION OF ASTEROIDAL GROUPS
R.V. Martins, NATIONAL OBSERVATORY RIO JANEIRO
(9) NEW DATA ON ASTEROIDS WITH LONG ROTATIONAL PERIODS
C.A. Angeli et al., NATIONAL OBSERVATORY RIO
JANEIRO
(10) COLLISION FREQUENCY OF SMALL METEORITES WITH CARS &
AIRCRAFTS
A. Poveda et al., UNIV NACL AUTONOMA
MEXICO
===================
(1) POSSIBILITY OF IMPACT IN 2044 & 2046 STILL VERY SMALL,
BUT ASTEROID 1999 AN10 NEEDS TO BE CAREFULLY
MONITORED
From Ron Baalke <baalke@ssd.jpl.nasa.gov>
http://neo.jpl.nasa.gov/news/news018.html
New Analyses Identify a Small Possibility that Asteroid 1999 AN10
Could Collide with Earth in 2044 or 2046
New orbital analyses for the kilometer-sized asteroid 1999 AN10
have
revealed a remote chance that this object might collide with the
Earth
in the year 2044 or 2046. Although this asteroid will be
monitored in
the future, it is not thought to be a serious hazard to Earth at
this
time. Researchers Andrea Milani, Steven Chesley and Giovanni
Valsecchi
in in Italy, as well the undersigned at JPL, have identified
these new
impacting possibilities by using new observational data, and by
projecting the asteroid's motion somewhat farther into the future
than
before. New measurements of 1999 AN10, made over the last
week and a
half by amateur astronomer Frank Zoltowksi in Australia, have
allowed
astronomers to make significantly more precise orbital
calculations,
and the revised predictions indicate that the asteroid could
approach
the Earth particularly closely on August 7, 2027. The orbital
motions
of the Earth and the asteroid do not permit a collision in 2027,
but
the close approach will certainly change the asteroid's orbital
path.
During the past week, researchers have focused on the range of
possible
paths the asteroid could follow after 2027.
The accompanying diagram (http://neo.jpl.nasa.gov/neo/an10a.gif)
shows
the uncertainty in the predicted close approach in 2027.
The asteroid
must pass through the plane of the diagram somewhere within an
extremely skinny uncertainty ellipse, which appears simply as a
line
segment. New measurements taken over the weekend have moved the
center
of the ellipse (the most likely point of passage) out to a
distance of
about 200,000 km from the Earth, significantly farther than last
week's
estimate. The predicted point of passage may continue to bounce
around
within the ellipse as new data are added, but it cannot decrease
below
a minimum of about 37,000 km from the Earth's center.
During the 2027 close approach, Earth's gravity will change the
asteroid's orbit by an amount which depends on the precise
location of
the point of passage through the uncertainty ellipse. In
particular,
a range of post-2027 orbital periods are possible: a passage on
the
left side of the Earth in this diagram will decrease the orbital
period;
a passage on the right side will increase the period. If the
asteroid
passes through certain narrow "keyholes" in the
uncertainty ellipse,
its changed orbit will bring it back for another Earth close
approach
in a later year. The 2039 impacting scenario identified by
Milani
et al. last month actually required passage through two keyholes,
one
in the 2027 ellipse, and one in the 2034 ellipse, which explains
why it
was so unlikely (about one chance in a billion using last month's
orbital estimate). This week's new observations have now
moved the
uncertainty ellipse completely off the 2039 keyhole, which
indicates
that this impacting scenario is no longer possible.
The newly identified impacting possibilities for August 6, 2044
and
August 7, 2046 each require passage through only a single keyhole
in the
2027 ellipse, and the probabilities of impact for these cases are
correspondingly larger, on the order of one chance in 500,000 for
2044,
and one chance in five million for 2046. These odds of
collision are
larger than those for any other object, but they are still less
than
one hundredth the chance of an undiscovered asteroid of
equivalent size
striking the Earth sometime before 2044. Asteroid 1999 AN10
therefore
does not pose a serious impact hazard at this time, but observers
should
continue to monitor its motion over the next few decades, and the
chance of impact should be carefully reassessed whenever new data
become available.
Paul W. Chodas
Research Scientist
Near Earth Object Program Office
Jet Propulsion Laboratory
May 26, 1999
================
(2) SPACEGUARD UK: QUESTION IN THE HOUSE OF LORDS
From Jonathan TATE <fr77@dial.pipex.com>
Dear All,
I thought that you might be interested in this extract from the
Lords'
schedule:
TUESDAY 15TH JUNE
* The Lord Janner of Braunstone—To ask Her Majesty’s
Government
what consultations they are proposing to carry out
concerning
the Middle East peace process.
* The Lord Roberts of Conwy—To ask Her Majesty’s
Government what
concordats have been agreed between the Welsh Assembly and
Government Departments.
†*The Lord Tanlaw—To ask Her Majesty’s Government
what steps are being
taken to form a National Spaceguard Agency, as part of a
European Spaceguard programme, to improve the assessment
and
probability factor of impact hazard of a Near Earth Object
on
the continent of Europe or in the seas surrounding it.
Progress!!
Jay Tate
Spaceguard UK
==============
(3) HOMO SAPIENS CAME CLOSE TO EXTINCTION - SEVERAL TIMES
From ABC News Online, 26 May 1999
http://abcnews.go.com/sections/science/DyeHard/dye990526.html
We Dodged Extinction
By Lee Dyw
Special to ABCNEWS.com
A worldwide research program has come up with astonishing
evidence
that humans have come so close to extinction in the past that it’s
surprising we’re here at all.
Pascal Gagneux, an evolutionary biologist at the University of
California at San Diego, and other members of a research team
studied
genetic variability among humans and our closest living
relatives, the
great apes of Africa.
Humanoids are believed to have split off from chimpanzees about 5
million to 6 million years ago. With the passage of all that
time,
humans should have grown at least as genetically diverse as our
“cousins.” That turns out to be not true.
“We actually found that one single group of 55 chimpanzees
in west
Africa has twice the genetic variability of all humans,”
Gagneux says.
“In other words, chimps who live in the same little group on
the Ivory
Coast are genetically more different from each other than you are
from
any human anywhere on the planet.”
The Family Bush
“The family tree shows that the human branch has been
pruned,” Gagneux
says. “Our ancestors lost much of their original
variability.”
“That makes perfectly good sense,” says Bernard Wood,
the Henry R. Luce
Professor of Human Origins at George Washington University and an
expert on human evolution.
“The amount of genetic variation that has accumulated in
humans is just
nowhere near compatible with the age” of the species, Wood
says. “That
means you’ve got to come up with a hypothesis for an event
that wiped
out the vast majority of that variation.”
The most plausible explanation, he adds, is that at least once in
our
past, something caused the human population to drop drastically.
When
or how often that may have happened is anybody’s guess.
Possible
culprits include disease, environmental disaster and conflict.
Almost Extinct
“The evidence would suggest that we came within a cigarette
paper’s
thickness of becoming extinct,” Wood says. Gagneux, who has
spent the
last 10 years studying chimpanzees in Africa, says the
implications are
profound.
“If you have a big bag full of marbles of different colors,
and you
lose most of them, then you will probably end up with a small bag
that
won’t have all the colors that you had in the big bag,”
he says.
Similarly, if the size of the human population was severely
reduced
some time in the past, or several times, the “colors”
that make up our
genetic variability will also be reduced.
If that is indeed what happened, then we should be more like each
other, genetically speaking, than the chimps and gorillas of
Africa.
And that’s just what the research shows.
“We all have this view in our minds that we [humans] started
precariously as sort of an ape-like creature” and our
numbers grew
continuously, adds Wood. “We’re so used to the
population increasing
inexorably over the past few hundred years that we think it has
always
been like that.” But if it had, Gagneux notes, our genetic
variability
should be at least as great as that of apes.
A Stormy Past
Gagneux is the lead author of a report that appeared in the April
27
issue of the Proceedings of the National Academy of Sciences. The
study, carried out with researchers in Germany, Switzerland and
the
United States, is the first to examine large numbers of all four
ape
species in Africa.
“We can do that now because new technology allows us to
non-invasively
take some hair, or even some fruit that these apes chew, and then
we
get their DNA from a couple of cells that stick to a hair or a
piece of
fruit they chewed.”
Then they compared the DNA variability of apes and chimps to that
of
1,070 DNA sequences collected by other researchers from humans
around
the world. They also added the DNA from a bone of a Neanderthal
in a
German museum. The results, the researchers say, are very
convincing.
“We show that these taxa [or species] have very different
amounts and
patterns of genetic variation, with humans being the least
variable,”
they state. Yet humans have prevailed, even though low
genetic
variability leaves us more susceptible to disease.
“Humans, with what little variation they have, seem to
maximize their
genetic diversity,” Gagneux says. “It’s ironic,”
he notes, that after
all these years the biggest threat to chimpanzees is human
intrusion
into their habitats. When he returned to Africa to study a group
of
chimps he had researched earlier, Gagneux found them gone.
“They were dead,” he says, “and I mean the whole
population had
disappeared in five years.” Yet as our closest living
relatives, chimps
still have much to teach us about ourselves.
Copyright 1999, ABC News
==============
(4) 'LOST CONTINENT' DISCOVERED
From the BBC Online Network, Thursday, May 27, 1999
http://news.bbc.co.uk/hi/english/sci/tech/newsid_353000/353277.stm
By BBC News Online Science Editor Dr David Whitehouse
Scientists have discovered the remains of a "lost
continent" beneath
the waves of the Indian Ocean.
Drilling by the Joides Resolution research vessel, which
traverses the
seas extracting samples from beneath the sea floor, suggests that
the
continent, about a third the size of present day Australia, sank
from
sight only 20 million years ago.
FULL STORT at
http://news.bbc.co.uk/hi/english/sci/tech/newsid_353000/353277.stm
==============
(5) DON'T FALL FOR THIS MISERABLE SERMON: US EVANGELIST PREACHES
APOCALYPTIC MESSAGE OF NEO-FATALISM
From CNN, 25 May 1999
http://cnn.com/SHOWBIZ/News/9905/25/showbuzz/
~~~~~~~~~~~
SHOWBIZ
~~~~~~~~~~~
Jim Bakker: Warning Solid Rock about space boulder
VENTURA, California (CNN) -- Former televangelist Jim Bakker says
the
much-discussed threat of the Y2K computer bug will be a
"Sunday picnic"
compared to the asteroid he envisions crashing into the Earth and
blocking out the sun and moon.
"All I say is don't fall in love with this world,"
Bakker told a
capacity crowd Sunday at the Solid Rock Christian Center.
Bakker's "PTL Club" television ministry collapsed in
the 1980s when it was
learned that he'd had an affair with secretary Jessica Hahn and
paid her with
church money to conceal it.
Now 59, Bakker spent close to five years in prison for swindling
$158
million out of his followers. He says the loss of his ministry,
homes, and
wealth made him think "God was gone," but that prison
taught him that faith
pulls people through hard times.
Copyright 1999, CNN
==============
(6) ON THE DYNAMICAL EVOLUTION OF ATENS AND APOLLO ASTEROIDS
R. Dvorak*) & E. Pilat Lohinger: On the dynamical evolution
of the
Atens and the Apollos. PLANETARY AND SPACE SCIENCE, 1999, Vol.47,
No.5,
pp.665-677
*) UNIVERSITY OF VIENNA,INST ASTRON,TURKENSCHANZSTR 17,A-1180
VIENNA,AUSTRIA
In this investigation we compare the dynamical evolution of the
two
groups of Earth crossing asteroids namely the Atens which
move-grosso
mode-inside the orbit of the Earth and the Apollos which move
outside
the Earth's orbit. The main goal of this study was to compute the
encounters of these asteroids with the Earth, respectively the
collision probabilities. We also briefly analyzed their
qualitative
behavior over one million years and computed the mixing of the
two
groups. The approach to achieve these results was a purely
numerical
one: we used extensive numerical integrations in the framework of
a
dynamical model of the planetary system (consisting of the Sun
and the
planets Venus through Saturn). Other interesting features of the
dynamics of Apollos and Atens are confirmed in our study-e.g. the
temporary capture into the 1:1 mean motion resonance with the
Earth.
Close encounters with the inner planets (primarily with the Earth
and
with Venus) are the major events which change the orbit of such
an
asteroid, but the Kozai resonances and the secular resonances
have to
be taken into account to understand the dynamical evolution over
longer
time intervals. The results of collision probabilities with the
Earth
are in good agreement with statistically derived results by other
authors: approximately 20 (50 for smaller objects) collisions for
each
Aten and 10 collisions for each Apollo per 1 billion years. (C)
1999
Elsevier Science Ltd. All rights reserved.
===============
(7) THE DIAMETER DISTRIBUTION OF EARTH-CROSSING ASTEROIDS
A. Poveda*), M.A. Herrera, J.L. Garcia, K. Curioca: The diameter
distribution of Earth-crossing asteroids
PLANETARY AND SPACE SCIENCE, 1999, Vol.47, No.5, pp.679-685
*) UNIV NACL AUTONOMA MEXICO,INST ASTRON,CIUDAD UNIV,MEXICO CITY
04510,DF,MEXICO
A cumulative distribution function N(d) of diameters of ECAs is
derived
by fitting an exponential function to the observed distribution
of
absolute magnitudes for the brightest objects (H less than or
equal to
15.5), where there is evidence of completeness. This luminosity
function can be transformed (with appropriate albedos and
densities) to
the frequency distribution of diameters, masses and energies. The
distribution of masses thus found is consistent with the
self-similar
theoretical distribution of masses subject to a steady-state
regime of
collisions found by Dohnanyi, and by Williams and Wetherill. The
frequency of collisions with the earth of asteroids of a given
diameter
or energy is calculated. (C) 1999 Elsevier Science Ltd. All
rights
reserved.
===========
(8) COLLISIONAL EVOLUTION OF ASTEROIDAL GROUPS
R.V. Martins: Collisional evolution - an analytical study for the
non
steady-state mass distribution. PLANETARY AND SPACE SCIENCE,
1999,
Vol.47, No.5, pp.687-698
NATIONAL OBSERVATORY,R GEN JOSE CRISTINO 77,BR-20921400 RIO
JANEIRO,RJ,BRAZIL
To study the collisional evolution of asteroidal groups we can
use an
analytical solution for the self-similar collision cascades. This
solution is suitable to study the steady-state mass distribution
of the
collisional fragmentation. However, out of the steady-state
conditions,
this solution is not satisfactory for some values of the
collisional
parameters. In fact, for some values for the exponent of the mass
distribution power law of an asteroidal group and its relation to
the
exponent of the function which describes 'how rocks break' we
arrive at
singular points for the equation which describes the collisional
evolution. These singularities appear since some approximations
are
usually made in the laborious evaluation of many integrals that
appear
in the analytical calculations. They concern the cutoff for the
smallest and the largest bodies. These singularities set some
restrictions to the study of the analytical solution for the
collisional equation. To overcome these singularities we
performed an
algebraic computation considering the smallest and the largest
bodies
and we obtained the analytical expressions for the integrals that
describe the collisional evolution without restriction on the
parameters. However, the new distribution is more sensitive to
the
values of the collisional parameters. In particular the
steady-state
solution for the differential mass distribution has exponents
slightly
different from 11/6 for the usual parameters in the Asteroid
Belt. The
sensitivity of this distribution with respect to the parameters
is
analyzed for the usual values in the asteroidal groups. With an
expression for the mass distribution without singularities, we
can
evaluate also its time evolution. We arrive at an analytical
expression
given by a power series of terms constituted by a small parameter
multiplied by the mass to an exponent, which depends on the
initial
power law distribution. This expression is a formal solution for
the
equation which describes the collisional evolution. Furthermore,
the
first-order term for this solution is the time rate of the
distribution
at the initial time. In particular the solution shows the
fundamental
importance played by the exponent of the power law initial
condition in
the evolution of the system. (C) 1999 Elsevier Science Ltd. All
rights
reserved.
==========
(9) NEW DATA ON ASTEROIDS WITH LONG ROTATIONAL PERIODS
C.A. Angeli*), D. Lazzaro, M.A. Florczak, A.S. Betzler, J.M.
Carvano:
A contribution to the study of asteroids with long rotational
period.
PLANETARY AND SPACE SCIENCE, 1999, Vol.47, No.5, pp.699-714
(*) NATIONAL OBSERVATORY,DEPT ASTROFIS,RUA GAL JOSE CRISTINO
77,BR-20921400 RIO JANEIRO,BRAZIL
We report the results of new photometric and/or spectroscopic
observations of 22 asteroids, selected among a sample of presumed
slow
rotators. All the available previous estimations of their
rotation
periods give values larger than 12 h. It has been recently
suggested by
Harris (1994) that some of these asteroids could be in a motion
of
non-principal axis rotation, due to a primordial excited state.
The
observations reported here were carried on at the Observatorio do
Pico-dos-Dias (Brazil), at the Observatoire de Haute-Provence
(France),
and at the European Southern Observatory (Chile). More than 60
single
night lightcurves were obtained. Rotation periods and the
corresponding
composite lightcurves were obtained for 5 objects. Spectroscopic
observations were also carried on to increase the knowledge on
these
objects and verify the hypothesis of a common origin. We have
obtained
reflectivity spectra covering 0.5-0.9 mu m for 18 objects with
orbital
semi-major axes between 2.23 and 3.15 AU. For most of them (11)
the
spectra suggest a C-type composition, and for the others an S or
E-type. Between the C-type asteroids, all but two show features
associated with an aqueous alteration process. (C) 1999 Elsevier
Science Ltd. All rights reserved.
==================
(10) COLLISION FREQUENCY OF SMALL METEORITES WITH CARS &
AIRCRAFTS
A. Poveda*), M.A. Herrera, J.L. Garcia, A. Hernandez Alcantara,
K.
Curioca: The expected frequency of collisions of small meteorites
with
cars and aircraft. PLANETARY AND SPACE SCIENCE, 1999, Vol.47,
No.5,
pp.715-719
*) UNIV NACL AUTONOMA MEXICO,INST ASTRON,CIUDAD UNIV,MEXICO CITY
04510,DF,MEXICO
The cumulative distribution N(d) of diameters of Earth-Crossing
Asteroids (ECAs) derived by Poveda et al. (1998, submitted) is
used to
estimate the frequency of collisions of meteoroids with cars and
with
aircraft. The expected frequency of collisions of a car with a
meteorite larger than 10 cm in diameter turns out to be one
impact
every 16 years. This frequency is consistent with the known
incidence
of such events (Lewis, 1996). The expected frequency of
collisions of a
cruising airplane with a meteorite larger than 1 cm in diameter
turns
out to be one impact every 30 years. Such an impactor hitting an
airplane at a velocity of several hundreds of meters per second
could
cause a serious accident. (C) 1999 Elsevier Science Ltd. All
rights
reserved.
----------------------------------------
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*
ASTEROID POSES GREATER FUTURE THREAT
From SPACEVIEWS: THE ONLINE PUBLICATION OF SPACE EXPLORATION
http://www.spaceviews.com/1999/05/25b.html
25 May 1999
A near-Earth asteroid which earlier this year was found to have a
one-in-a-billion chance of striking the Earth in 2039 may have a
larger
-- but still very small -- chance of a collision five years
later,
JPL astronomers said.
In an interview with MSNBC, Don Yeomans, head of NASA's
Near-Earth
Object Program Office at JPL, said that asteroid 1999 AN10 has a
1-in-500,000 chance of hitting the Earth in 2044.
That probability is still less than that for a unknown asteroid.
Astronomers estimate a 1-in-100,000 chance that an undiscovered
asteroid one kilometer or larger in diameter will strike the
Earth in a
given year.
However, that very small probability has raised interest among
astronomers. "I’m not worried in the least about this
object, but I’m
not going to ignore it," Gareth Williams of the Minor
Planets Center
told MSNBC. Yeomans said the asteroid's impact probability is at
a
threshold above which it might warrant special attention.
The revised orbit for 1999 AN10 came after new observations of
the
asteroid by an amateur astronomer in Australia. Those
observations were
likely triggered by debate in April when a preprint of a
scientific
paper, publicized on a mailing list used by near-Earth asteroid
researchers, showed that the asteroid had a one-in-a-billion
chance of
colliding with the Earth in 2039.
The revised calculations based on the new data also increased the
probability of a 2039 impact to ten million to one, 100 times
higher
than previously but still far smaller than the odds of an impact
from
an unknown object.
The asteroid will also make a close flyby of Earth in 2027,
coming as
close as 32,600 km (20,200 mi.) of the surface of the Earth on
August
7. The chance of an impact on that date is essentially zero, but
the
close passage the asteroid, within the Earth's magnetic field,
might
levitate dust off the surface of the asteroid through
electrostatic
repulsion and create a dim "dust coma."
Astronomers earlier noted that the asteroid's orbit will bring it
close
to Earth many times in the coming centuries. Further observations
of
the asteroid are planned in coming weeks that should refine its
orbit
and better determine any impact probabilities in future close
approaches.
Copyright 1999, spaceViews
