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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