PLEASE NOTE:


*

CCNet, 7 October 1999
------------------------


(1) NEW OBSERVATIONS BY AUSTRALIAN ASTRONOMER DISPEL IMPACT   
    THREAT
    Benny J Peiser <b.j.peiser@livjm.ac.uk>

(2) SOUTH AFRICAN CRATER IDENTIFIED AS WORLD'S LARGEST IMPACT  
    STRUCTURE
    SpaceDaily, 5 October 1999

(3) PUZZLE OF COMETARY ORBITS HINTS AT LARGE UNDISCOVERED OBJECT
    Jacqueline Mitton <jmitton@dial.pipex.com>

(4) ASTRONOMERS DISCOVER MOON ORBITING ASTEROID
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(5) MARTIAN METEORITE CARBONATES 3.9 BILLION YEARS OLD
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(6) ACCURATE PREDICTIONS OF LEONID METEOR STORMS
    Benny J Peiser <b.j.peiser@livjm.ac.uk>

(7) INTERPLANETARY BIOTIC TRANSFER
    Michael Paine <mpaine@tpgi.com.au>



=========
(1) NEW OBSERVATIONS BY AUSTRALIAN ASTRONOMER DISPEL IMPACT   
     THREAT

From Benny J Peiser <b.j.peiser@livjm.ac.uk>

The history of public impact threat announcements repeats itself, or so
it would seem. When a potential impact risk posed by asteroid 1997 XF11
was announced 18 months ago, it took just 24 hours before new (or, to
be precise, old) observational data were able to eliminate the threat
completely. Now, a similar impact threat announcement (although on a
much smaller scale than the initial 1:50,000 impact probability of
XF11) has been annuled within two days. 

New observations of asteroid 1999 RM45 made by Australian astronomer
Rob McNaught and published yesterday by the Minor Planet Center in
Cambridge, Mass. (http://cfa-www.harvard.edu/mpec/J99/J99T22.html) now
provide a 21-day arc of orital data which practically rule out any
impact risk for the next five decades. The effect of these new
observations have reduced the orbital uncertainty by a factor of ten.
It would thus appear that the small impact possibilities suggested for
2042 and 2050 by Steve Chesley and his colleagues at Pisa University
have now completely disappeared.
 
I understand that the next possible close approach to the earth (based
on the the 21-day arc) is in September 2012. Further observations
during the next couple of months should clarify this situation. Unless
the NEO search community will get use of a large telescope, there will
be no chance of any further observations until the year 2008.

Benny J Peiser

P.S. I note with some lack of understanding that the NeoDys impact risk
page at http://newton.dm.unipi.it/neodys/1999RM45.risk.html, still
features the 2042/2050 impact calculations from Monday although Rob
McNaught's new observations have been known for almost two days. It be
wiser and less confusing, I believe, to up-date such impact-threat
announcemnets regularily.

==================
(2) SOUTH AFRICAN CRATER IDENTIFIED AS WORLD'S LARGEST IMPACT  
    STRUCTURE

Fom SpaceDaily, 5 October 1999
http://www.spacedaily.com/spacecast/news/spaceguard-99g.html

World's Largest Impact Found In South Africa

Johannesburg (AFP) October 5, 1999 - South African geologists have
identified a crater in central Free State province to be the oldest and
largest in the world caused by the impact of a comet or an asteroid,
scientists said.

World renowned University of the Witwatersrand (Wits)
paleo-anthropologist Philip Tobias told a public lecture on human
evolution here that the Vredefort crater, which is between 250 and 300
kilometers (150 and 190 miles) in diameter, was long thought to be of
volcanic origin.

However, geologists, led by Wits professor Uwe Reimold, had recently
shown that the structure was caused by the impact of an
extra-terrestrial object such as an asteroid or comet, Tobias said
Wednesday.

"It is the largest impact structure that has yet been identified on
planet Earth. It exceeds even the Sudbury crater in Ontario, Canada,
which is about 200 kilometers (125 miles) in diameter," he said.

"Not only is the Vredefort crater the biggest so far identified on
Earth, but it is the oldest. It has been dated to 2.1 billion years."

The town of Vredefort is situated at the centre of the crater, which is
bigger than the Chicxulub depression made by an asteroid or comet at
Yucatan, in Mexico. The Chicxulub collision is thought to have caused the
extinction of most of the dinosaurs.

"Like Chicxulub, Vredefort may well have been a major catastrophe whose
worldwide consequences had an enormous impact on the history of life on
Earth," Tobias said.

Reimold told AFP that the way minerals in the crater had been deformed
indicated the indentation could not have been caused by volcanic
activity.

Initial estimates, he added, indicated that the crater could have been
caused by a comet or asteroid five to 10 kilometers (three to six
miles) in diameter, travelling at a speed of between 40,000 and 250,000
kilometers (25,000 and 150,000 miles) an hour.

According to Reimold, the impact on the Earth's atmosphere could well
have caused a setback of a few million years in the evolution of life
as it existed at the time.

The crater is so old and eroded, however, that it is difficult, except
in a few places, to see the effect of the impact with the naked eye.

Scientists at both Wits and Potchefstroom, southwest of Johannesburg,
who are working jointly on the project, say many studies remain to be
undertaken at Vredefort.

The site has been known since the turn of the century, but only dated
in 1996, and only in the past few years has it been suspected that it
was caused by a collision.

Copyright 1999 AFP & SpaceDaily. All rights reserved

==================
(3) PUZZLE OF COMETARY ORBITS HINTS AT LARGE UNDISCOVERED OBJECT

From Jacqueline Mitton <jmitton@dial.pipex.com>

ROYAL ASTRONOMICAL SOCIETY
PRESS NOTICE

Date: 7 October 1999                                    
For immediate release

Ref. PN 99/32
Issued by: Dr Jacqueline Mitton
RAS Press Officer
Phone: Cambridge  ((0)1223) 564914
FAX: Cambridge ((0)1223) 572892
E-mail: jmitton@dial.pipex.com

RAS Web: http://www.ras.org.uk/ras/

* * * * * * * * * * * * * * * * * * * * * * * *

CONTACT FOR THIS RELEASE

Dr John B. Murray (j.b.murray@open.ac.uk)
Phone: 01908 652118

Dept. of Earth Sciences, The Open University,
Milton Keynes MK7 6AA

* * * * * * * * * * * * * * * * * * * * * * * * *


PUZZLE OF COMETARY ORBITS HINTS AT LARGE UNDISCOVERED OBJECT

Intrigued by the fact that long-period comets observed from Earth seem
to follow orbits that are not randomly oriented in space, a scientist
at the Open University in the UK is arguing that these comets could be
influenced by the gravity of a large undiscovered object in orbit
around the Sun. Writing in the issue of the Monthly Notices of the
Royal Astronomical Society published on 11th October, Dr John Murray
sets out a case for an object orbiting the Sun 32,000 times farther
away than Earth. It would, however, be extremely faint and slow moving,
and so would have escaped detection by present and previous searches
for distant planets.

Long-period comets are believed to originate in a vast 'reservoir' of
potential comets, known as the Oort cloud, surrounding the solar system
at distances between about 10,000 and 50,000 astronomical units from
the Sun. (One astronomical unit is approximately the average distance
between the Earth and the Sun.) They reach Earth's vicinity in the
inner solar system when their usual, remote orbits are disturbed. Only
when near to the Sun do these icy objects grow the coma and tails that
give them the familiar form of a comet. Dr Murray notes that the comets
reaching the inner solar system include a group coming from directions
in space that are strung out along an arc across the sky. He argues
that this could mark the wake of some large body moving through space
in the outer part of the Oort cloud, giving gravitational kicks to
comets as it goes.

The object would have to be at least as massive as Jupiter to create a
gravitational disturbance large enough to give rise to the observed
effect, but currently favoured theories of how the solar system formed
cannot easily explain the presence of a large planet so far from the
Sun. If it were ten times more massive than Jupiter, it would be more
akin to a brown dwarf (the coolest kind of stellar object) than a
planet, brighter, and more likely to have been detected already.

So Dr Murray speculates that such an object, if it exists, will be
planetary in nature and will have been captured into its present orbit
since the solar system formed, even though the probability of such an
event seems low on the basis of current knowledge.

Though a large, distant planet is a fascinating possibility and the
evidence is suggestive, Dr Murray nevertheless stresses that he is not
ruling out other possible explanations for the observed clustering of
the comet orbits.

=================
(4) ASTRONOMERS DISCOVER MOON ORBITING ASTEROID

From Andrew Yee <ayee@nova.astro.utoronto.ca>

Southwest Research Institute


CONTACT:
Dr. William J. Merline
(303) 546-0487 or merline@boulder.swri.edu

Maria Martinez
(210) 522-3305 or mmartinez@swri.org

Astronomers discover moon orbiting asteroid

New technology promises to revolutionize our understanding of
asteroid makeup

Boulder, Colorado, October 7, 1999 -- An international team of
astronomers has  discovered a moon orbiting the asteroid (45)Eugenia.
The pictures, taken with the Canada-France-Hawaii Telescope (CFHT)
on Mauna Kea, Hawaii, are the first images of an asteroidal satellite
taken from Earth. The team's findings will be reported in the October 7
issue of Nature.

Previous attempts to photograph such satellites, using both
ground-based telescopes and the Hubble Space Telescope, found no
satellites. The only other  such picture came from an interplanetary
spacecraft, Galileo, when it discovered the small moon, now known as
Dactyl, around asteroid (243)Ida in 1993. The observations could only
be accomplished because of a new technique, called adaptive optics,
that reduces the blurring caused by the Earth's atmosphere.

A surprising result of this discovery is the very low density of the
primary asteroid -- only about 20 percent denser than water. Most
asteroids appear dark and were thought to be composed primarily of
rock, which is about three times denser than water. "A picture is
emerging that some asteroids are real lightweights," said Dr. William
Merline, leader of the team, and a senior research scientist at the
Boulder office of San Antonio-based Southwest Research Institute
(SwRI). A recent flyby of the NEAR spacecraft confirmed that another
asteroid, (253)Mathilde, also has a low density. "Either these
objects are highly porous rubble-piles of rock, or they are mostly
water ice," said Dr. Clark Chapman, another team member, also from
SwRI.

The presence of a moon allows scientists to determine the mass of an
asteroid because of the effect of the primary asteroid's gravity on
its small moon. The size of most asteroids is known from standard
astronomical studies. If both the mass and the size are known,
researchers can learn the asteroid's density. The density then gives
a clue to the asteroid's makeup -- either in terms of composition or
structure.

"If these asteroids are rubble-piles, it tells us about the severity
of collisions in the asteroid belt and its subsequent evolution. If
the objects are largely ice, covered with a dark-coating, then these
objects may be remnants of burned-out comets and will further our
understanding of the connection between comets and asteroids," said
Dr. Christophe Dumas of the Jet Propulsion Lab in Pasadena.

"It is almost certain that the satellite was formed by a collision,"
said Merline. "As we know from the formation of our own moon and the
craters on planetary surfaces, collisions played a large role in the
formation of our solar system. Satellites of asteroids give us a
window into these collisions, and help us understand how and why our
solar system looks like it does."

The light from stars and other celestial objects is distorted by the 
atmosphere, much as water distorts our view of an underwater object.
The new technique, pioneered at the University of Hawaii by team
member Dr. Francois Roddier, analyzes the distortions and corrects
the light beam by means of what is essentially a "fun-house mirror"
back into its previous, undistorted form. "CFHT's exceptional site,
telescope, and adaptive optics now allow us to see far sharper detail
through the Earth's atmosphere. In many cases we can now compete with
the clarity of space-based telescopes," said Roddier. The instrument
used was built by the CFHT Corporation.

Previously, faint and close satellites would have been lost in the
glare of the primary asteroid. "It is similar to taking a photo of a
candle located 400 km away and then discovering a firefly (that is
300 times fainter) flying within two meters of the flame," said Dr.
Laird Close, a participant from the European Southern Observatory
(ESO) in Germany.

The results are the first from a program to search for satellites
around nearly 200 asteroids. "If more satellites are found, it will
revolutionize our understanding of the makeup of asteroids," said
Merline.

"Except for a few of the very largest asteroids, this is the only way
that asteroid densities can be determined other than by spacecraft
flybys," according to Close.

Eugenia orbits the sun in the main asteroid belt, a collection of
thousands of asteroids that exists between the orbits of Mars and
Jupiter. Asteroids are thought to be bodies that never formed a
planet; the gravity of the giant planet Jupiter may have stirred up
the bodies enough that they collided with each other at fast speeds,
perhaps either fragmenting or forming satellites, rather than
colliding gently, adhering, and gradually building up a planet.

Researchers estimate that the diameter of the satellite is about 13
kilometers. Eugenia's diameter is about 215 kilometers. The
researchers have determined that the satellite has a circular orbit
about 1,190 km away from Eugenia. It orbits about once every five
days.

While awaiting assignment of a permanent name, the satellite has been
given provisional designation, by the International Astronomical
Union, of S/1998(45)1, the first satellite of asteroid (45) that was
discovered during 1998.

This work was funded by NASA and the U.S. National Science
Foundation. A portion of the image processing and data analysis was
carried out using facilities at the ESO. CFHT is funded by the
National Research Council (NRC) of Canada, the Centre National de la
Recherche Scientifique (CNRS) of France, and the University of
Hawaii.

Other team members and affiliations are Dr. Francois Menard, CFHT;
Dr. David Slater, SwRI headquarters in San Antonio; Dr. Gilles
Duvert, Laboratoire d'Astrophysique in Grenoble, France; Dr. Chris
Shelton, W.M. Keck Observatory, Hawaii; and Dr. Tom Morgan, NASA
Headquarters, Washington, D.C.

EDITORS: Images to support this story are available after 2 PM EDT,
Wednesday, October 6, 1999, on the Internet at:
   www.boulder.swri.edu/~merline/press_release

===================
(5) MARTIAN METEORITE CARBONATES 3.9 BILLION YEARS OLD

From Andrew Yee <ayee@nova.astro.utoronto.ca>

John Ira Petty
Johnson Space Center, TX Oct. 1, 1999
(281) 483-5111

MARTIAN METEORITE CARBONATES 3.9 BILLION YEARS OLD

A new study of the carbonate minerals found in a meteorite from Mars
shows they were formed about 3.9 billion years ago. Scientists believe
the planet had flowing surface water and warmer temperatures then,
making it more Earth-like. Giant meteorites were blasting huge craters
in its surface.

This study doesn't directly address the possibility that life once
existed on Mars. But "It's another piece in the puzzle," said Larry E.
Nyquist of the Planetary Sciences Branch of Johnson Space Center's
Earth Science and Solar System Exploration Division. Nyquist, one of
the authors of an article in Science, a weekly publication of the
American Association for the Advancement of Science, was the principal
investigator.

Researchers at Johnson Space Center in Houston and the University of
Texas at Austin did the study, using different techniques. Both
produced similar results, establishing the carbonates' age within
comparatively narrow limits.

The 4.2 pound meteorite is believed to be part of an igneous rock
formation formed about 4.5 billion years ago as Mars solidified from a
molten mass. The meteorite probably was blasted from the planet when a
huge comet or asteroid struck Mars 16 million years ago.

It fell in Antarctica about 13,000 years ago, and was found in 1984 by
an annual expedition sponsored jointly by NASA, the National Science
Foundation, and the Smithsonian Institution. Called ALH84001, after the
Allan Hills in Antarctica where it was found, it was returned to
Johnson Space Center, and has been preserved at the Meteorite
Processing Laboratory there.

It subsequently was recognized as one of more than a dozen meteorites
with unique Martian characteristics.

Just how the carbonates were deposited within this igneous rock is the
topic of lively debate. Some scientists believe water saturated with
carbon dioxide from the atmosphere seeped down to the subsurface site
where the igneous rock formed and created the carbonate deposits. On
Earth, living organisms often play a role in carbonate formation. In
1996 scientists at Johnson Space Center and Stanford University
examined the carbonates in ALH84001 using electron microscopy and laser
mass spectrometry, and reported evidence suggesting primitive life may
have existed in them.

Other scientists believe the carbonates formed when hot,
carbon-dioxide-bearing fluids were forced into cracks in the rocks when
a meteor struck Mars. The 3.9-billion-year age of the carbonates
eliminates neither possibility.

The carbonates themselves are tiny deposits, reddish globules, some
with purplish centers and many surrounded by white borders. The
different colors are due to variations in the compositions of the
carbonates: purplish manganese-bearing calcium carbonate, reddish iron
carbonate, and white magnesium carbonates. The globules were found
along fractures in the meteorite and make up about 1 percent of its
volume.

The JSC-UT team, using a binocular microscope and tools resembling
dental picks, over a period of months painstakingly separated out
enough of the carbonate material for their analyses. After
experimenting with terrestrial calcium, iron, and magnesium carbonates,
they developed a way to selectively dissolve carbonate material of
differing compositions, enabling them to separate different elements
from the carbonate solutions.

The study established the age of the carbonate deposits by measuring
the decay of rubidium to strontium and of uranium to lead. The
techniques are similar to carbon dating, which is used for much shorter
time periods. The investigators used the dual approach because "we
wanted to make sure we had a result we could believe in and that other
people could believe in," Nyquist said.

The leading author of the Science article is Lars E. Borg, formerly of
the National Research Council and Johnson Space Center and now at the
University of New Mexico in Albuquerque. Other authors are James N.
Connelly of the University of Texas at Austin, Chi-Yu Shih, Henry
Weismann, and Young Reese, of Lockheed Engineering and Science in
Houston. K. Manser of the University of Texas contributed to the
investigation.

The age of the carbonates, said Everett K. Gibson of Johnson Space
Center and an author of the 1996 study that reported evidence of
microbial life in the carbonates, had been "one of the real mysteries"
of indications of life on Mars. Had the carbonates been formed more
recently, when the planet's surface was devoid of water, it would have
been unlikely they were associated with primitive life on Mars. Dating
them at 3.9 billion years, when there apparently was surface water on
Mars is, Gibson said, very important, and could "suggest events were
very similar in the inner solar system" as primitive life arose.

==================
(6) ACCURATE PREDICTIONS OF LEONID METEOR STORMS

From Benny J Peiser <b.j.peiser@livjm.ac.uk>

Talk by David Asher (Armagh Observatory):
Accurate predictions of Leonid meteor storms

Wednesday, 13 October, 4pm

Astrophysics Research Institute, Liverpool John Moores University,
Twelve Quays House, Egerton Wharf, Birkenhead, L41 1LD,
 
It has often been regarded as difficult to predict exactly when the
most spectacular meteor storms occur.  But in fact, orbital
integrations can be used to derive the timings to high accuracy. Here, 
such a technique is applied to the Leonids, which have produced many of
the best storms in the past two centuries.  The Leonid parent, Comet
55P/Tempel-Tuttle, returns to perihelion every 33 years or so and
generates a trail of meteoroids and dust. The dynamical evolution of
each trail is calculated, since these narrow trails represent the
highest density regions of the stream, and storms occur when the Earth
passes near the centre of a trail.

The Armagh Observatory's web page about the Leonids can be found at

   http://www.arm.ac.uk/leonid/

================
(7) INTERPLANETARY BIOTIC TRANSFER

From Michael Paine <mpaine@tpgi.com.au>

Dear Benny,

The "debate" in your posting of 6 October 1999 seems to ignore the
discovery of "nanobes" by Dr Philippa Uwins from Queensland University.
This was described in CCNET on 23 Mar and 30 Mar 1999. In brief, Dr
Uwins found what appear to be dormant organisms in rock samples taken
from several km underground (115 to 170 C and 2000 atm). Filaments grew
when exposed to normal temperatures and pressures and a source of
nutrients. The nanobes are about 20 nanometres in diameter (she notes
"the same size range as the controversial fossil nanobacteria in
Martian meteorite ALH84001"), appear to have cellular walls and test
positive to DNA staining. If this work is confirmed then it has major
implications for "interplanetary biotic transfer" - an organism that
could survive the rigours of space-flight on a meteorite (blast-off ,
interplanetary cruising and re-entry). Also such organisms could
survive the "planet-sterilizing" huge impacts of the early Earth in
refuges deep underground.

see http://www1.tpgi.com.au/users/tps-seti/swaprock.html for links.

Michael Paine

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