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



CCCMENU CCC for 1999

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