PLEASE NOTE:


*

CCNet, 19 November 1999
-----------------------


     QUOTE OF THE DAY

     "So we can indeed celebrate and claim that today we acquired our
     200th known TNO. But we don't know what that means."
          --Brian G. Marsden, 18 November 1999


(1) 200 TRANSNEPTUNIAN OBJECTS
    Harvard-Smithsonian Center for Astrophysics

(2) PREDICTION OF LEONIDS WAS SPOT-ON
    Jacqueline Mitton <aco01@dial.pipex.com>

(3) LEONID ACTIVITY 1999 - AN UPDATE
    Marc Gyssens" <gyssens@charlie.luc.ac.be>

(4) NASA CLAIM CREDIT FOR PREDICTING RIGHT TIME OF LEONID STORM PEAK
    NASANEWS <nasanews@mail.arc.nasa.gov>

(5) DID ASTEROID-INDUCED FIRESTORMS DESTROY THE DINOSAURS?
    Michael Paine <mpaine@tpgi.com.au>

(6) NEW BOOK ON NEOS AVAILABLE
    Christian Gritzner <gritzner@eurospace.de>

(7) JUPITER'S CHILLY PAST
    Michael Paine <mpaine@tpgi.com.au>

(8) NATURE CAUSED SAHEL DROUGHT
    BBC Online Network, 18 November 1999

(9) DISCOVERY OF ASTEROIDAL MOON
    W.J. Merline et al., SW RESEARCH INSTITUTE

=============
(1) 200 TRANSNEPTUNIAN OBJECTS

From the Harvard-Smithsonian Center for Astrophysics
http://cfa-www.harvard.edu/cfa/ps/pressinfo/200TNOs.html

PRESS INFORMATION SHEET: Produced at the Harvard-Smithsonian Center for
Astrophysics (CfA), Cambridge, Massachusetts, U.S.A.

Hard on the heels of the announcement last week of the discovery of the
200th potentially hazardous asteroid, the announcement was made today
of the discovery of the 200th member of the Transneptunian Belt. Also
known as the Kuiper Belt or the Edgeworth-Kuiper Belt, the
Transneptunian Belt is a collection of bodies orbiting the sun
generally at distances somewhat larger than that of Neptune.

As with the PHA discoveries, the rate of TNO discoveries has increased 
very dramatically recently. Fully half of the TNOs have been found
during just the last 12 months, with the first discovery having been in
1992 or 1930, according as to whether one does not or does choose to
consider Pluto to be a member. Whether one does or does not include
Pluto does not affect today's milestone, because the seven new objects
being announced take the count well over 200.

While the rate of new TNO discoveries is gratifying, this greatly
increases the problem of obtaining enough follow-up observations to 
ensure a reliable prediction for the next opposition--and then ensuring
that recovery observations are then made. Some 61 percent of the TNOs
with an opportunity so far for recovery have in fact been observed at a
second opposition. Such success is actually quite encouraging, given
that the observations at the discovery opposition have often been
extremely meager, and that the orbit solutions are almost invariably
complete guesswork. Although a second opposition is necessary for a
reliable orbit determination, it is hardly sufficient, and continued
occasional monitoring is very much in order. The recent recovery
announcement of 1998 UU43 consisted of data on two consecutive nights
last week of an object observed last year on one night in October and
another in December. At least one of the presumed multiple-opposition
TNOs, 1995 YY3, now appears to be lost.

It has been usual to separate the TNOs into two principal groups,
namely, what are called the "classical Kuiper Belt objects", or
"cubewanos" (this name arising from the designation 1992 QB1 of their
prototype), with orbits of rather low eccentricity (though with
inclinations up to 30 degrees or so) and mean distances between 42 and
47 AU from the sun (Neptune being at a distance of 30 AU); and the
"plutinos" (Pluto itself being the prototype), their mean distances of
39 AU giving them orbits having revolution periods that are
three-halves that of Neptune, this resonance in fact preventing close
approaches to Neptune, even though orbital eccentricities up to more
than 0.3 mean that these objects can cross Neptune's orbit. Almost 50
percent of the objects with good orbit determinations are cubewanos,
and almost 40 percent are plutinos. It also seems that 5 percent or so
have revolution periods that are twice that of Neptune, so they have
mean distances of 48 AU, the rather large orbital eccentricities again
allowing these objects to approach Neptune's orbit--but not Neptune
itself. There are also a couple of resonant objects with revolution
periods that are four-thirds and five-thirds that of Neptune.

The remaining well-observed TNO, 1996 TL66, ranges in distance between
35 AU and 135 AU from the sun. There are certainly other objects of
this type, sometimes called "scattered-disk objects", although only
four of the single-opposition objects, all of them discoveries in
February 1999, have officially been assigned scattered-disk orbits. It
is highly probable that several of the lost TNOs are actually in this
category--which would help explain why they are lost, because
scattered-disk status would very considerably augment the amount of sky
needed to be searched to guarantee their recovery.

One can argue that the count of PHAs is arbitary because the rules
defining a PHA are also arbitrary. But we can at least be sure that the
accepted PHAs meet those rules. Given that only 34 percent of the
currently known TNOs have been observed at more than one opposition, we
cannot really provide a satisfactory definition for a TNO that we can
guarantee will be met by the majority of the objects that have been
classed as TNOs. Certainly, we seem to be on reasonably firm ground
when it comes to the established cubewanos and plutinos (and also
perhaps the other resonant objects), but beyond that there is a
problem.

Part of the problem is that there is at some level really no dynamical
distinction between a scattered-disk object and a centaur. A centaur is
an object that in some way moves in the general range of the giant
planets. Although Chiron, which in 1977 was the first such discovery,
currently moves rather neatly between the orbits of Saturn and Uranus,
close approaches to these planets can change this. But half of the 16
objects classified as centaurs actually have their farthest points from
the sun beyond the orbit of Neptune--i.e., into the domain of the TNOs.
One of these objects, 1995 SN55, is currently well beyond Neptune, at
39 AU from the sun. Its classification as a centaur is quite arbitrary,
and it could equally well be classified as a TNO: it is probably not a
plutino or other "regular" TNO, but it could easily have been
classified as a scattered-disk TNO. So if we are going to consider
scattered-disk objects as part of the TNO population, we really should
also include at least part of the centaur population.

The combined population therefore has well over 200 members--more than
220 if all the centaurs are included. Then there is the recent 1999
TD10, which we know to be currently just beyond the orbit of Saturn,
well inside the "centaur region", but that at its farthest from the sun
is quite akin to 1996 TL66 and the other scattered-disk objects. It is
"both" a centaur and a TNO, but it is currently being classified as
neither.

Finally, there is the matter of the comets. We know that Chiron shows
cometary attributes, and it is classified both as a centaur, with the
asteroid number (2060), and a comet, with the designation 95P/Chiron.
It is widely believed that the centaurs and TNOs generally are
protocomets. There are other comets, such as 29P/Schwassmann-Wachmann 1
and 39P/Oterma, with current orbital characteristics that could also
allow them clearly to be classified as centaurs. Furthermore, less than
half a century ago, the orbit of 39P/Oterma, then inside the orbit of
Jupiter, was much like those of many of the other short-period comets,
notably, D/1993 F2 (Shoemaker-Levy 9), the string of objects that
crashed into Jupiter in 1994.

So we can indeed celebrate and claim that today we acquired our 200th
known TNO. But we don't know what that means.

Brian G. Marsden

1999 November 18

E-mail: bmarsden@cfa.harvard.edu

=======================
(2) PREDICTION OF LEONIDS WAS SPOT-ON

From Jacqueline Mitton <aco01@dial.pipex.com>

ROYAL ASTRONOMICAL SOCIETY
PRESS NOTICE

PREDICTION OF LEONIDS WAS SPOT-ON

Date: 18 November 1999
For immediate release

Ref. PN 99/35

ISSUED BY:

Dr Jacqueline Mitton
RAS Press Officer
Office & home phone: Cambridge ((0)1223) 564914
FAX: Cambridge ((0)1223) 572892
E-mail: jmitton@dial.pipex.com


RAS web: www.ras.org.uk/ras/press/press.htm

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

CONTACT FOR THIS RELEASE

Professor Mark Bailey (meb@star.arm.ac.uk)
Armagh Observatory, College Hill, Armagh, BT61 9DG
Tel: 028-3752-2928, Fax: 028-3752-7174


MORE INFORMATION

on the Armagh Observatory Leonid web site:
http://www.arm.ac.uk/leonid/index.html

on the European Southern Observatory web site:
www.eso.org/outreach/info-events/leonids99/

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

Preliminary results from observations of last night's Leonid meteor 
storm indicate that the prediction made by Dr David Asher of Armagh 
Observatory and Rob McNaught of the Australian National University of a
strong shower peaking at around 2.08 a.m. UT (or GMT) were spot on - 
even to the extent that faint meteors would dominate compared with the
exceptional fireball display last year. This is the first time that
astronomers have succeeded in making such an accurate prediction of a
meteor storm.

The peak rate of meteors is more difficult to predict than the time of
maximum. Asher and McNaught had been cautious with their public
statements, but had reason to believe from their latest work that it
could be higher than the 20 per minute they had been suggesting. The
preliminary observations seem to show that a higher rate did indeed
occur.

'We are delighted with this vindication of the method used by Rob and
David', said Professor Mark Bailey, Director of the Armagh Observatory.
The only cause for regret in the UK today was that most of the country
was blanketed in cloud at the crucial time.

Attention will now be focussed on their prognostications for the next
three years. Next year (2000), they predict, will be 'the calm before
the storm': the Earth will pass through the centre of the broad
meteoroid stream without passing directly through any of the dense,
recently ejected dust trails. 'It's rather like the ten-pin bowler who,
having left half a dozen pins standing after the first shot, bowls
clean through the gaps with the second shot' said Professor Bailey.

Next year's observations will, however, be important for gathering
further observational information about the location and extent of the
dust trails. The Earth will pass, for the first time ever, through the
outskirts of the dust trail deposited when Comet Tempel-Tuttle made its
appearance in 1866. This trail could prove to be denser than expected.

The showers in 2001 and 2002 are expecte to be dominated by close
encounters of the Earth with this 1866 trail. Predictions based on
their present model lead to zenithal hourly rates well in excess of
10,000 meteors per hour. Actual observations in 2000 should help to
determine whether this is correct, or an under- or over-estimate.

========================
(3) LEONID ACTIVITY 1999 - AN UPDATE

From Marc Gyssens" <gyssens@charlie.luc.ac.be>

     -------------------------------------

     I M O   S h o w e r   C i r c u l a r

     -------------------------------------


             LEONID Activity 1999
             ====================
                    UPDATE
             ====================

New ZHR calculations have been made. On the one hand, newly received
observations have been included, and, on the other hand, data based on
estimated counts have been replaced by data based on actual counts.

Visual observations of the 1999 Leonids revealed a distinctive peak
with a ZHR of about 5000 on November 18, 2h04m +/-5m UT (solar
longitude 235.286 +/- 0.004, eq. 2000.0). Ten minutes earlier, at 1h53m
+/- 5m UT (solar longitude 235.278 +/- 0.004, eq. 2000.0), the ZHR
profile shows a secondary peak with of ZHR of about 3500. This
secondary peak does not only occur in the combined ZHR profile below,
but also in the ZHR profile of several individual observers, and is
therefore probably real. Apart from this secondary peak, the ZHR
profile looks remarkably smooth, even at the level of 5-minute
intervals.

ZHR levels were above 1000 from roughly 1h20m UT to 2h45m UT
corresponding to 235.26 to 235.31 degrees in solar longitude.

All observers who were able to view the peak under good sky conditions
reported an abundance of faint meteors and a relative absence of
fireballs. Some observers noticed a drop in the population index (i.e.,
a larger fraction of brighter meteors) after the peak.

Reports from Mohammad Odeh (Jordanian Astronomical Society), Casper ter
Kuile (Dutch Meteor Society, observing near Valencia, Spain), and Ilan
Manulis (Israel) are very consistent with the picture sketched  above.

In addition, radio data from K. Maegawa (Toyokawa Meteor Observatory,
Aichi, Japan) reported by Kazuhiro Suzuki and the backscatter radar
data from Ondrejov Observatory (Czech Republic) reported by Petr Pridal
and Rosta Stork yield a peak time between 2h00m UT and 2h10m UT.

It seems that the peak time of 2h08m UT predicted by Asher/McNaught is
confirmed within a margin of at most a few minutes, although the
observed activity is significantly higher. It is reasonable to conclude
that the peak activity has been caused by the 3-revolutions old dust
trail of 55P/Tempel-Tuttle.

The following observers (with their observing sites, not their
nationality or country of residence) have contributed data immediately
after the event, from which the ZHR profile given below has been
derived:

Rainer Arlt (Spain), Felix Betonvil (Canary Islands), C.L. Chan
(China), Mark Davis (USA), Asdai Diaz (Cuba), Yuwei  Fan (China),
Fei Gao (China), Lew Gramer (USA), Rafael Haag (Brazil), Dave Hostetter
(USA), Andre Knoefel (Spain), Detlef Koschny (Spain), Wen Kou (China),
Alastair McBeath (UK), Alfredo Pereira (Portugal), Josep Ma.
Trigo-Rodriguez (Spain), Helena Valero-Rodriguez (Spain), Renke Song
(China), Wanfang Song (China), Jan Verbert (France), Catarina Vitorino
(Portugal), Jean-Marc Wislez (France), Mariusz Wisniewski (Poland), Dan
Xia (China), Dongyan Zha (China), Jinghui Zhang (China), Yan Zhang
(China), Jin Zhu (China).

(For groups of observers, only the name of the contributing observers
have been mentioned.)

Date   Period (UT)  Time (UT)  Sol. Long.  ZHR +/-
-----------------------------------------------------------
Nov 17 0600-1000    0800       234.527       16     2
Nov 17 1600-2010    1805       234.951       30     5
Nov 17 1900-2200    2030       235.052       53    14
Nov 17 2300-2400    2330       235.178       82     6
Nov 18 0000-0050    0026       235.217      210    60
Nov 18 0030-0100    0048       235.233      370    80
Nov 18 0050-0130    0110       235.248      560    90
Nov 18 0115-0145    0132       235.263     1160   180
Nov 18 0139-0155    0148       235.275     2360   600
Nov 18 0145-0200    0153       235.278     3430   750
Nov 18 0154-0205    0158       235.282     2820   550
Nov 18 0159-0209    0204       235.286     5400   880
Nov 18 0200-0215    0209       235.289     3540   580
Nov 18 0212-0233    0222       235.298     2110   580
Nov 18 0223-0247    0238       235.310     1140   280
Nov 18 0244-0320    0257       235.323      690   150
Nov 18 0315-0400    0340       235.353      240    60
Nov 18 0347-0505    0423       235.383      153    59
Nov 18 0512-0712    0557       235.449       61    12
Nov 18 0700-1100    0905       235.581       44     5

ZHRs are computed with a population index of 2.0, zenithal exponent of
1.0.

---
Marc Gyssens, 1999 November 18, 7h UT.
wgn@imo.net

===============
(4) NASA CLAIM CREDIT FOR PREDICTING RIGHT TIME OF LEONID STORM PEAK

From NASANEWS <nasanews@mail.arc.nasa.gov>

STORMY NIGHT FOR ASTROBIOLOGISTS STUDYING LEONID METEORS

Kathleen Burton Nov. 18, 1999
NASA Ames Research Center, Moffett Field, CA
(Phone: 650/604-1731, 650/604-9000)  kburton@mail.arc.nasa.gov

Laura Lewis
NASA Ames Research Center, Moffett Field, CA
(Phone:  650/604-2162, 650/604-9000)  llewis@mail.arc.nasa.gov

RELEASE:  99-77
STORMY NIGHT FOR ASTROBIOLOGISTS STUDYING LEONID METEORS

Astrobiologists on a NASA mission to study the Leonid meteors were in
the right place at the right time to study a rare natural phenomenon --
a meteor storm.

At the peak of the storm, which occurred at 02:10 GMT, Nov. 18, the 
Leonid meteors were falling from the sky at a rate of 2,200 per hour. 
A meteor shower is classified as a storm when the rate exceeds 1,000
meteors per hour.

"It's getting to the point where we can't click fast enough to keep up 
with the meteors!" exclaimed Dave Holman of the California Meteor
Society, one of several amateur astronomers on the meteor-counting
team.  A total of 15,251 meteors were counted during the six-hour
observation period on the overnight flight from Israel to the Azores.

"That's a lot of meteors!" said Chris Crawford, the amateur astronomer
responsible for compiling the data collected from each person counting
the meteors.  "I've seen just about as many meteors in one night as
I've seen in over 34 years of meteor watching."

Near real-time data on the number of meteors falling per hour was
provided to NASA and the U.S. Air Force by a team of amateur
astronomers who counted the meteors using virtual reality goggles and
laptop computers.  The meteor counting team was aboard the ARIA, one of
two aircraft provided by the United States Air Force to support this
mission. The data was sent from the ARIA, an EC-18 aircraft, to the
ground via the TDRS satellite system. NASA and the Air Force are joint
sponsors of the Leonid Multi-instrument Airborne Campaign.

"I am ecstatic over how well this night went!" said Peter Jenneskins,
chief scientist for the Leonid mission. "Our models proved to be right
on for predicting where and when the meteor storm would take place. We
gathered some fantastic images, and the data obtained should provide
valuable insight into the role meteors may have played in the evolution
of life on Earth."

While viewing the horizon at one point during the storm, meteors,
lightning and sprites could be seen from the planes. Sprites are
lightning phenomena that rise from the ground to the sky. "For 10
minutes we had a view of the way the sky may have looked on Earth over
4 million years ago," Jenneskins said.  "It was an awesome sight."

The second observing night of the Leonid astrobiology mission began
when the ARIA and FISTA aircraft left Tel Aviv at about 23:00 GMT, Nov.
18. The flight crew of the ARIA reported seeing two meteors almost as
soon as the wheels left the ground. Once the planes reached altitude,
they began flying in 150 nautical mile flying patterns from east to
west over Israel and the Mediterranean. These orbits provided a unique
opportunity for scientists on the planes and scientists on the ground
to collaborate. The data collected from the planes will be combined
with visual, radar and radio observation data from Israeli scientists
on the ground to form an extremely comprehensive data set regarding the
Leonid meteors.

The aircraft stopped the orbits after one hour and continued westbound
towards the Azores, flying approximately 80-100 nautical miles apart at
37,000 feet. ARIA's path flew the scientists off the coast of Crete and
over Sicily, while FISTA's path flew over mainland Greece and the boot
of Italy. ARIA then flew over the top of Menorca and Majorca, crossed
central Spain by Madrid, and continued over the top of Portugal down to
the Azores. FISTA flew over Sardinia and Barcelona and out the
northwest corner of Spain, and then down to the Azores.  The planes
landed at Lajes Airbase in the Azores at approximately 07:15 GMT, Nov.
18.

While over Spain and Portugal, scientists on the aircraft performed
coordinated observations with a series of ground based observing teams.

"The coordinated air and ground observations that were conducted during
the flight are an invaluable part of this highly successful mission,"
stated Col. S. Pete Worden, of the United States Air Force
headquarters, Washington, D.C.  "Not only do we have a phenomenal set
of data from the air, but we also have complimentary data from the
ground that can be used to help us better understand and predict meteor
storms and the impact they may have on space operations."  Col. Worden
flew aboard the ARIA aircraft from Tel Aviv to the Azores. The Air
Force operates more than 100 satellites that could be affected by a
meteor storm.

It takes the Earth a few days to get through the debris trail left by
the periodic comet 55P/Tempel-Tuttle that produces the Leonid meteors.
Therefore, one more observation night is scheduled during a flight from
the Azores to Patrick Air Force Base in Florida.

The scientists and crew aboard the ARIA and FISTA are not the only
people able to see the Leonid meteors from the unique vantage-point of
an airplane. Live video from the plane is being sent to the internet
during the mission for people on the ground to watch. For current
information about the Leonid Multi-instrument Airborne Campaign visit:
http://leonid.arc.nasa.gov/

-end-
-----
SATELLITE FEED INFO FOR THIS STORY--
Video File for Nov. 18, 1999
11:00 am  (NASA TV)
ITEM 3 - LEONIDS 1999 IMAGES FROM NOV. 17 (replay)/AMES

ITEM 4 - LEONIDS 1998 PLUS 1999 INTERVIEWS FROM NOV. 16
         AMES/MSFC (replay)

ITEM 5 - SOLVE VIDEO FILE - ARC, LARC, DFRC

ITEM 6 - MARS MISSIONS CLIP REEL (file footage)

LIVE TELEVISION EVENTS THIS WEEK:

November 19, Friday

1:00 - 2:00 pm - Space Science Update on Results from First
Galileo Flyby of Jovian Moon, Io - HQ


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


ITEM 1 - POSSIBLE  NEW LEONIDS IMAGES FROM JERUSALEM
         (shot Nov. 17) - AMES

ITEM 2 - HIGH-ALTITUDE BALLOON VIDEO OF LEONIDS
         (shot Nov. 17) - MSFC

ITEM 3 - LEONIDS 1999 IMAGES FROM NOV. 17 (replay)/AMES

Contact at NASA Headquarters, Washington, DC:  Donald Savage
(Phone 202/358-1547).
Contact at NASA Ames Research Center, Moffett Field, CA:  Kathleen
Burton (Phone 650/604-1731).

 LIVE TELEVISION EVENTS THIS WEEK:

November 19, Friday

1:00 - 2:00 pm - Space Science Update on Results from First
Galileo Flyby of Jovian Moon, Io - HQ


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

ITEM 3a - 1999 LEONID B-ROLL-------------------------------TRT :42

Meteor streaks from the ARIA aircraft during the first night of
the 1999 Leonid Airborne Campaign.


ITEM 3b - INTERVIEW EXCERPTS------------------------------TRT 1:20

Jane Houston, U.S. Astronomer, Leonid Meteor Count Team

ITEM 4 - LEONIDS 1998 PLUS 1999 INTERVIEWS FROM NOV. 16
         AMES/MSFC (replay)
*****************************
TV Producers:
Please note all times, unless otherwise noted, are Eastern Time.
This heads-up announces our most current line-up of stories on
NASA's daily Video File feed. As we try to provide you the best,
most current service possible, THE LINE-UP MAY CHANGE THROUGHOUT
THE DAY.

Any CHANGES TO THE LINE-UP WILL APPEAR ON THE NASA VIDEO FILE
ADVISORY on the web at
ftp://ftp.hq.nasa.gov/pub/pao/tv-advisory/nasa-tv.txt
WE UPDATE THE ADVISORY THROUGHOUT THE DAY.

The NASA Video File normally airs at noon, 3:00 p.m., 6:00 p.m.,
9:00 p.m. and midnight Eastern Time. NASA Television is available
on GE-2, transponder 9C at 85 degrees West longitude, with
vertical polarization. Frequency is on 3880.0 megahertz, with
audio on 6.8 megahertz.
For general questions about the video file call NASA Headquarters,
Washington, DC: Ray Castillo 202/358-4555 or Elvia Thompson
202/358-1696.

================
(5) DID ASTEROID-INDUCED FIRESTORMS DESTROY THE DINOSAURS?

By Michael Paine

Special to space.com
http://space.com/science/astronomy/dinosaurs_fry_991118.html
Nov 18 1999

Dinosaurs may have met their demise in a global firestorm of methane
gas triggered by an asteroid impact, a team of scientists reports in
the latest issue of Geo-Marine Letters.

The methane gas was released from the Earth by the asteroid collision
and ignited by lightning, says Naval Research Laboratory scientist
Barton Hurdle.

Hurdle told space.com that he and several colleagues put forth the idea
-- a fiery end to Earth's greatest land creatures -- before various
teams of researchers in 1991 and 1992 theorized that a crater
discovered in Mexico was the site of an asteroid impact responsible for
the mass extinctions.

"It shook up the ocean, generated tsunamis that ruptured pockets of
methane that were trapped under gas hydrates, and it also created
slumping -- a sliding down of the ocean bottom -- that released (the
methane) too," Hurdle said.

"This stuff came out, lightning set it afire, and it burned," Hurdle
explained. "There were fantastic quantities of this stuff."

The theoretical fire would have burned near the ground and high into
the atmosphere, Hurdle said, enveloping much of the planet as shock
waves from the impact moved through the planet and dislodged methane
around the globe.

"The atmosphere itself would have been on fire," Hurdle and his
colleagues wrote in the paper.

The fire would have incinerated land creatures, he said, while
decreasing oxygen supplies and increasing the amount of carbon dioxide
in the atmosphere.

"There was a lot of soot, and that soot has been found," Hurdle said.

The theory, also featured in this week's issue of New Scientist
magazine, stems from the discovery of vast deposits of methane, a
carbon-based molecule, under the sea floor that are locked in crystals
of water ice, forming "methane hydrate."

Marine geologist Erwin Suess and co-workers from the Research Center
for Marine Geosciences in Germany estimate the total amount of carbon
locked in these deposits exceeds the amount in all of the known coal,
oil and gas reservoirs. What is more, methane hydrate is very unstable
and releases methane if the temperature or pressure rises slightly
above that existing under the seafloor.

Interest, and skepticism

Brown University's Peter Schultz, who studies impact craters and the
processes that create them, says Hurdle's idea definitely merits further
study.

"The observation that there are these methane traps on the bottom of
the ocean is pretty well established," Schultz told space.com. He said
that while an ocean impact could certainly release this methane, he's
not sure if the affect would be over a large enough area to release
enough methane to cause the scenario Hurdle describes.

"My reservation is whether or not the shock wave could have released as
much methane as they say," Schultz said.

And as planetary scientists John Lewis and Sidney van Den Bergh point
out, there are several other dire consequences of the impact, (the site
is known as the Chicxulub crater), that could explain the extinction of
the dinosaurs. The methane hydrate proposal is seen by many researchers
as credible, but may in fact have been a nail in the coffin rather than
the exact cause.

Evidence and likelihoods

There is ample evidence of a global firestorm at the time of the
Chicxulub impact. Iridium-bearing clay in the boundary layer between
the Cretaceous Period (a time when dinosaurs roamed) and Tertiary
Period (the subsequent geologic time frame when dinosaurs seem to have
disappeared) contains soot.

The quantity and composition of the soot corresponds to the burning of
at least 50 percent of the world's forests. Although Hurdle's idea that
methane fires were responsible for this firestorm is plausible, there
is another simpler explanation.

The Chicxulub impact would have launched millions of tons of rock into
ballistic space flight. Over the following hour this debris would have
re-entered the Earth's atmosphere at high speed, causing millions of
brilliant "shooting stars." The radiant heat from these meteors alone
would have been sufficient to ignite the trees around the world.

This idea is supported by the discovery of charcoal in tsunami deposits
near the impact site. The best explanation may be that the trees were
ignited by radiant heat, then swamped soon after by the waves.

The shock wave from the impact would indeed have triggered massive
earthquakes in the region and indirectly triggered other earthquakes
around the globe. A tsunami would have formed from the impact, which
occurred in a shallow sea. The giant waves would also have been
generated by the earthquakes and undersea landslides triggered by the
shock wave.

"Megawaves emanating from an impact site would circuit the earth at
high speeds andcause worldwide disruption in the entire ocean in a
single day," Hurdle and his colleagues wrote.

Acid rain and a long, long winter

Researchers say the impact fireball and the forest fires would have
created huge quantities of nitrogen oxides, which react with water vapor
to form acid rain. By chance, the Chicxulub asteroid struck rocks with
an unusually large proportion of calcium sulfate. This would have
generated sulfur dioxide -- another source of acid rain. There are
several signs of a massive dose of acid rain at the time, including
sudden weathering of continental rocks.

The dust thrown up by the impact, the soot generated by the firestorms
and the smog formed from the oxides of nitrogen and sulfur particles
would have blocked sunlight for many months. The surface of the Earth
would have plunged to freezing conditions -- typically 70 degrees
Fahrenheit below normal -- and photosynthesis would not have been
possible, even if plants had survived the fires and acid rain.

Global warming

After several months the dust would have settled and sunlight would
have begun heatingup the land. Now the greenhouse effect would have
taken over due to the excess of carbon dioxide created by the fires and
the melting of limestone rocks at the impact site.

Methane released from ocean sediments could have added to the
greenhouse effect. It has been estimated that the surface temperatures
on Earth were at least 10 degrees Fahrenheit above normal for hundreds
of thousands of years after the impact.

So dinosaurs, if they were not consumed in a firestorm, would have had
to live through a torturous sequence of events -- from the barbecue to
the freezer, to a dip in acid andthen a hothouse baking. Regardless of
whether Hurdle's idea is correct, it agrees with mounting evidence that
suggests how a massive asteroid impact at Chicxulub may have been the
fatal blow to the dinosaurs, as well as 50 percent of all the Earth's
species.

space.com's Robert Roy Britt contributed to this report
c1999 Space.com

================
(6) NEW BOOK ON NEOS AVAILABLE

From Christian Gritzner <gritzner@eurospace.de>

Hi Benny,

My book "Kometen und Asteroiden - Bedrohung aus dem All?" has just
been published and is available by now !!!

It is written in German and intended for the general public. It is
about what comets, asteroids, meteors, etc. are, why they pose a
threat to mankind, how often collisions of comets and asteroids
with the Earth happen, and what could be done to prevent future
impacts on Earth. By the way, an analysis of planetary defense
systems was the topic of my Thesis in 1996. The book has over 100
pages and contains more than 90 pictures mostly in color. The
price is DM 39,80.

The foreword was written by Dr. Gerhard J. Hahn (DLR Berlin),
scientific PI of the O.D.A.S. program and board member of
Spaceguard Foundation e.V. in Germany.

Further information (in German) is available from the publisher's
homepage:

http://www.aviatic.de (-> aktuelles) or directly:
http://www.aviatic.de/buch/3-925505-53-9.html

Best wishes,
Christian

Dr.-Ing. Christian Gritzner
EUROSPACE Technische Entwicklungen GmbH
Lindenstr. 6
D-14467 Potsdam
E-mail: gritzner@eurospace.de

============
(7) JUPITER'S CHILLY PAST

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

Dear Benny,

The NASA news release posted on CCNet on 18 Nov described the
possibility, amongst several, that Jupiter formed in a much colder
region of the solar system. The September issue of Scientific American
had an article Migrating Planets

(online at http://www.sciam.com/1999/0999issue/0999malhotra.html )

which describes a possible mechanism for large scale planetary
migration.
 
Michael Paine

PS: the night sky is now clear but it seems that the Leonids are
running on time and there is not much hope of a spectactular display
over Sydney in the early hours.
===============
(8) NATURE CAUSED SAHEL DROUGHT

From the BBC Online Network, 18 November 1999
http://news.bbc.co.uk/hi/english/sci/tech/newsid_527000/527040.stm

NATURE CAUSED SAHEL DROUGHT

By BBC Science's Toby Murcott

A massive drought that struck parts of Northern Africa in the 1970s and
80s may have been the result of a natural climate cycle.

Up to now, many scientists thought the drought in the Sahel zone was
caused by humans over-using natural resources in the region.

But a new study in the journal Science shows how a combination of ocean
temperature and loss of natural vegetation could have been the sole
reasons for the drought.

The drought pushed the Sahara desert south, destroying farmland. It had
a major impact on many countries including Nigeria, Niger and Mali.

Now, scientists from the Nasa Goddard Space Flight Centre and the
University of California in Los Angeles believe it could all be
explained by natural phenomena.

Computer simulation

The researchers produced a computer model that included ocean surface
temperature, the amount of moisture in the soil, and loss of
vegetation.

With all those conditions, the computer model behaved just like the
Sahel drought - producing a long period of dry, cool weather.

It appears that human activity might not have been to blame for the
drought, and the study suggests the Sahel region may be naturally prone
to such large climate changes.

The challenge now is whether that information will help scientists
predict when the next drought is likely to occur.

Copyright 1999, BBC

===============
(9) DISCOVERY OF ASTEROIDAL MOON

W.J. Merline*), L.M. Close, C. Dumas, C.R. Chapman, F. Roddier, F.
Menard, D.C. Slater, G. Duvert, C. Shelton, T. Morgan: Discovery of
a moon orbiting the asteroid 45 Eugenia. NATURE, 1999, Vol.401,
No.6753, pp.565-568

*) SW RESEARCH INSTITUTE,BOULDER,CO,80302

Evidence for asteroidal satellites (moons) has been sought for decades,
because the relative frequency of such satellites will bear on the
collisional history of the asteroid belt and the Solar System, yet only
one has been detected unambiguously(1-3). Here we report the discovery
of a satellite of the asteroid 45 Eugenia, using an adaptive optics
system on a ground-based telescope. The satellite has a diameter of
about 13 km, and an orbital period of about 4.7 days with a separation
of 1,190 km from Eugenia. Using a previously determined(4) diameter for
Eugenia, we estimate that its bulk density is about 1.2 g cm(-3), which
is similar to that of the C-type asteroid Mathilde(5,6). This implies
that Eugenia, also a low-albedo C-type asteroid, may be a rubble pile,
or composed of primitive, icy materials of low bulk density. Copyright
1999, Institute for Scientific Information Inc.

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