PLEASE NOTE:
*
CCNet 132/2001 - 10 December 2001
================================
"On several occasions, I and other critics of the IAU
guidelines
have requested that the 72-hour review should not take place (for
a
Torino nonzero object) until the current observations have ended
(at
which point it may not be necessary, of course). At the same
time, I have
pointed out that the IAU should not issue any public statement
about impact
probabilities that are prone to change due to additional data
coming in. It
is time that the IAU WGNEO complies with its assurance that the
defective
guidelines will be revised effectively. No more excuses,
please."
--Benny J Peiser, 10 December 2001
(1) ROYAL ASTRONOMICAL SOCIETY DEBATES ASTEROID THREAT
Jacqueline Mitton <aco01@dial.pipex.com>
(2) STOKE OF LUCK: HOW ANOTHER ASTEROID SCARE WAS PREVENTED
Benny J Peiser <b.j.peiser@livjm.ac.uk>
(3) THE RISE AND FALL OF NEA 2001VK5
David Morrison <dmorrison@arc.nasa.gov
>
(4) WEIRED GEMINIDS
NASA Science News, 7 December 2001
(5) NASA TO DISCUSS LEONIDS, MARS AND EARLY EARTH AT AGU
Ron Baalke <baalke@jpl.nasa.gov>
(6) PLANETARY SCIENCE AT THE AGU MEETING
Michael Paine <mpaine@tpgi.com.au>
(7) NASA GODDARD JOINS TEAM TO EXPLORE THE SOLAR SYSTEM'S FINAL
FRONTIER
Andrew Yee <ayee@nova.astro.utoronto.ca>
(8) 'RESTLESS EARTH' MAY GIVE ADVANCE NOTICE OF LARGE EARTHQUAKES
Andrew Yee <ayee@nova.astro.utoronto.ca>
(9) SPACE MEMORIAL FOR 11 SEPTEMBER
BBC Online News, 10 December 2001
(10) MIOCENE OCEAN IMPACT?
Michael Paine <mpaine@tpgi.com.au>
(11) KING DAVID'S COMET & IMPACT
Göran Johansson <swe99acad@tjohoo.se>
(12) THERA AND THEOGONY
Bruce Lerro <goethe48@pacbell.net>
(13) NEW WORKING PAPER ON DISASTER MANAGEMENT
John Twigg <j.twigg@UCL.AC.UK>
(14) AND FINALLY: FIRE SCARE GONE MAD - SCIENTIST WANTS TO BAN
CHRISTMAS
TREES
Ananova, 8 December 2001
===========
(1) ROYAL ASTRONOMICAL SOCIETY DEBATES ASTEROID THREAT
>From Jacqueline Mitton <aco01@dial.pipex.com>
ROYAL ASTRONOMICAL SOCIETY - PRESS NOTICE
Date: 10 December
2001
Ref. PN 01/32
Issued by: Dr Jacqueline Mitton (RAS Press Officer)
Phone: +44 ((0)1223) 564914
Mobile phone on meeting day: 07770 386133
Fax: +44 ((0)1223) 572892
E-mail: jmitton@dial.pipex.com
RAS web: http://www.ras.org.uk
Contacts for this release:
Dr Duncan Steel (University of Salford)
Phone: 0161 295 3981
Email: D.I.Steel@salford.ac.uk
Mobile phone on 13 and 14 December: 07967 949 342
Professor Mark Bailey (Armagh Observatory)
Phone: 028 3752 2928
Email: meb@star.arm.ac.uk
Mobile phone on 13 and 14 December: 07765 256 346
ROYAL ASTRONOMICAL SOCIETY DEBATES ASTEROID THREAT
Action being taken by the UK government, the United Nations and
the European
Space Agency to further our understanding of the hazard posed by
near Earth
objects (NEOs) in space are on the agenda at Royal Astronomical
Society
meetings in London on Friday 14 December. The meetings are open
and media
representatives are cordially invited. (For details of times and
locations
see below.)
Dr Colin Hicks, Director of the British National Space Centre,
will talk
about the UK government's policy on NEOs. In 2000, the UK
government set up
a Task Force to consider the threat from potentially-hazardous
NEOs. Its
detailed report (available on-line at http://www.nearearthobjects.co.uk/)
made 14 recommendations for government action.
Dr Hans Haubold, Director of the UN Office for Outer Space
Affairs in
Vienna, will discuss the past and future involvement of the
United Nations.
The NEO hazard is a global problem, requiring international as
well as
national responses. The first step is to map the orbits of the
larger
asteroids in the solar system. This can be done using quite
modest
telescopes, so smaller countries can make vital contributions.
Dr Marcello Coradini, Coordinator of Solar System Missions at the
European
Space Agency's headquarters in Paris, will explain ESA¹s plans
for space
missions to study the physical nature of asteroids and comets.
NASA already
has several such spacecraft either on the way or planned for
launch within
the next few years. ESA's Rosetta mission, the first designed to
go into
orbit around a comet, is scheduled for launch in 2003.
Other contributors will describe how UK astronomers and space
researchers
plan to become involved with the international Spaceguard
programme, how the
NEO impact hazard ranks against other large-scale potential
disasters (such
as nuclear power station accidents), and how the media deal with
this topic.
Meeting co-organiser, Dr Duncan Steel said, " This is
astronomy 'close to
home'. Only recently has the importance of comets and asteroids
to our own
planet been recognised. But quite apart from potential impact
catastrophes,
NEOs are worlds in their own right. Studying them is becoming a
central
feature of solar system exploration. The next few years promise a
wealth of
interesting information on asteroids and comets."
PROGRAMME
Discussion meeting in the GEOLOGICAL SOCIETY LECTURE THEATRE,
BURLINGTON
HOUSE, Piccadilly, London W1
10:30 Introductory comments and overview: Duncan
Steel
10:45 Alan Fitzsimmons (Queen's University, Belfast)
Observing NEOs with
UK-supported ground-based telescopes
11:10 Peter Wheatley (University of Leicester)
NEOs in the UK
Wide-field Automated Survey Programe (WASP)
11:25 John Zarnecki (Open University)
NEO-related Research
at the Open University
11:45 Sarah Dunkin (Rutherford Appleton
Laboratory)
Inner-Earth NEO
searches using BepiColombo
12:00 Wyn Evans (University of Oxford)
GAIA: A Census of the
Solar System
12:20 Phil Palmer (University of Surrey)
Research at Surrey
University for a NEO mission: Affordable Access
for Science in Space
12:40 Apostolos Christou (Armagh
Observatory)
Nearer than the Moon:
dynamics and future opportunities for NEO
missions
13:00 - 14:00 Lunch break
14:00 Nigel Holloway (Spaceguard UK)
NEO Impacts: Risk
Perceptions and Realities
14:20 Benny Peiser (Liverpool John Moores
University)
Asteroid Scares:
Near-Earth Objects and the Media
14:35 Iain Gilmour (Open University)
The ESF-Impact
programme: current objectives and future directions
14:55 Colin Hicks (Director,
British National Space Centre)
Government Policy and
Future Plans on NEOs
15:20 Concluding remarks: Mark Bailey
15:30 - 16:00 Break and CHANGE OF VENUE
16:00 - 18:00 RAS monthly Astronomy and Geophysics meeting
at the
SCIENTIFIC SOCIETIES' LECTURE THEATRE, SAVILE ROW, London W1
(entrance in
New Burlington Place)
approx. 17.15 Hans Haubold (Director, UN Office for Outer Space
Affairs,
Vienna)
United Nations Initiatives on NEOs
approx. 17. 35 Marcello Coradini (Coordinator, Solar System
Missions, ESA)
ESA's contribution to the understanding of NEOs and
their related problems
MORE INFORMATION, INTERVIEWS
For comment, general information about the meetings, or to get in
touch with
individual speakers, contact the meeting organisers:
Dr Duncan Steel
Joule Physics Laboratory
University of Salford
Greater Manchester, M5 4WT
Phone: 0161 295 3981
Fax: 0161 295 5147
Email: D.I.Steel@salford.ac.uk
Mobile phone contact for Thursday and Friday: 07967 949 342
Professor Mark Bailey
Armagh Observatory
College Hill
Armagh BT61 9DG,
Phone: 028 3752 2928
Fax: 028 3752 7174
Email: meb@star.arm.ac.uk
Mobile phone contact for Thursday and Friday: 07765 256 346
===================
(2) STOKE OF LUCK: HOW ANOTHER ASTEROID SCARE WAS PREVENTED
>From Benny J Peiser <b.j.peiser@livjm.ac.uk>
One year ago, on November 3 2000, the IAU and NASA released a
statement
which announced that the Earth faced a small risk of being hit by
a near
Earth object (2000 SG344) in 2030. The next day NASA and the IAU
had to
retract their press announcement because additional observations
had
eliminated the risk altogether. The rushed and unnecessary
announcement was
due to IAU guidelines which request that a "significant
impact risk" (i.e.
NEOs that score 1 or higher on the Torino Scale) should be made
public after
72 hours if verified.
The main mistake with the SG344 announcement was in the way
information
about essentially correct computations was published prematurely
and despite
the knowledge that observers were still searching their files for
pre-discovery data. As a result of the embarrassing fiasco,
officials of the
IAU Working Group on NEOs promised that the flawed guidelines
would be
revised accordingly so that a repetition of the mistake would be
impossible.
After the 344SG debacle, not surprisingly, there was mounting
pressure to
make effective changes to the IAU guidelines. After all, the IAU
guidelines
foolishly stipulate that "If the consensus of the [IAU]
review supports the
conclusion that there is a significant impact risk, the results
of this
analysis will be posted on the IAU webpage at http://www.iau.org/ for public
access at the same time the information is released by the
authors to the
public."
That this procedure is extremely harmful and in need of change is
reflected
in a year-old assurance on the IAU website which states that
"The procedures
for these reviews are currently under revision. Hence the
following
information, while being a correct and complete description of
the system
that is now in use, is only to be regarded as temporary and will
probably be
updated before the end of March 2001" ("Hazardous NEO
Technical Reviews "
http://web.mit.edu/rpb/wgneo/TechComm.html).
Yet in spite of these public
assurances, no such revisions have been implemented.
The failure to learn the lessons from the SG344 fiasco (and
previous
asteroid scares) and which have caused unnecessary distress to
the public
means that we may expect new cases of false alarms at any time.
As David
Morrison reports below, another damaging asteroid scare was
recently averted
largely due to good luck.
Of course, I am very pleased that asteroid 2001 VK5 was
eliminated as a
potential threat before an official announcement was published on
the IAU
website. On the other hand, it would appear that the positive
outcome is a
result of fortuity rather than wise decision making. In short, I
am not
entirely convinced that the handling of the 2001 VK5 peer review
was an
"example of the proper functioning of the IAU Technical
Review", as David
Morrison claims.
Once again, the crucial quandary points to the notorious 72 hours
period
before an official pronouncement is recommended by the IAU
guidelines.
Thankfully, the members of the WGNEO decided to turn a blind eye
to the IAU
guidelines and decided "to defer any announcement from the
IAU until after
the USA Thanksgiving holiday." If the existing IAU
guidelines had been
followed, the 72-hour rule would have kicked in, meaning that
after the
formal review of impact calculations for 2001 VK5 had confirmed a
significant impact risk, the verification of the risk would have
be
published on the IAU website. Some media outlets, most likely,
would have
picked up the story and made headlines with it, and a few days
later the
same media could have been making fun of astronomers as once
again a small
impact probability was reduced to zero by new observations.
With another stoke of good luck, new observations of 2001 VK5 had
eliminated
all of the remote impact possibilities before the end of the
Thanksgiving
holiday, "and 2001VK5 had dropped back to a category zero in
the Torino
impact scale."
Morrison's description of events, I'm afraid to say, sounds
almost as if he
intended to issue a public announcement on the IAU website in
case 2001 VK5
had remained a Torino 1 object (or higher) after the Thanksgiving
holiday.
In short, had 2001 VK5 not been eliminated, we might have ended
up with yet
another unnecessary alarm. The likelihood of a VI remaining on
level 1 of
the Torino Scale over a number of weeks doesn't seem too
unrealistic.
Indeed, the question has to be asked what would have happened if
the impact
probability of 2001 VK5 had temporarily increased to level 2 or
higher on
the Torino Scale?
On several occasions, I and other critics of the IAU guidelines
have
requested that the 72-hour review should not take place (for a
Torino
nonzero object) until the current observations have ended (at
which point it
may not be necessary, of course). At the same time, I have
pointed out that
the IAU should not issue any public statement about the impact
probabilities
that are prone to change due to additional data coming in.
Of course, I don't want to be too critical with the IAU technical
team who
have done a good job after all. Nevertheless, I think it would be
wise not
keep in mind the existing pitfalls of the current IAU guidelines
which are
in great need of augmentation. Here are just some recommendations
that come
to mind:
1. The IAU should no longer "encourage" researchers to
submit Torino Level 1
(and higher) virtual impactors for technical review as long as
the object is
observable and thus very likely to be eliminated as a potential
threat by
additional data.
2. Virtual impactors should only be submitted for review once it
is clear
that no new data will eliminate the risk, or no new data is
obtainable.
3. If virtual impactors are submitted for review, the review team
should
request time for further observational data to be obtained before
making any
statements.
4. The Torino Scale should no longer be used as a yardstick for
deciding
whether not not to go public.
It is time that the IAU WGNEO complies with its assurance that
the defective
guidelines will be revised effectively. No more excuses, please.
Benny J Peiser
===============
(3) THE RISE AND FALL OF NEA 2001VK5
>From David Morrison <dmorrison@arc.nasa.gov
>
NEO News (12/07/01) 2001VK5 and DPS/AAS
THE RISE AND FALL OF NEA 2001VK5
I would like to report briefly on some recent actions of the
International
Astronomical Union Working Group on NEOs concerning the new NEA
2001VK5,
discovered on 11 November 2001 and initially announced through
Minor Planet
Electronic Circular 2001-V49. This example illustrates the
operations of the
IAU technical review process as well as the generally excellent
cooperation
of NEA observers and theorists in dealing with a new asteroid
that initially
appears to be on an orbit that could lead to a subsequent impact
with the
Earth. The great majority of such cases, of course, will turn out
to pose no
threat as additional observations become available. This is such
an example.
Andrea Milani and his team in Pisa calculated an orbit for VK5
and noted
that the initial results with such a short arc yielded an
enormous number of
"Virtual Impactors (VIs)"; their algorithms detected
more than 1,000
separate impact pathways, for impacts between 2002 and 2080. The
list was
made progressively available on the web, as their computers were
producing
the output, starting on 14/11/2001; in the same day the SGF
Central Node
launched a "new campaign" to ensure adequate followup.
This object was
reobserved on 16/11/2001. By the late hours of 17/11, Milani had
calculated
a new list of VIs, with fewer individual impactors but with more
significant
probabilities, including a November 2011 Virtual Impactor had a
probability
(computed with uniform probability density) of 4.6e-7. This
object was of
estimated H magnitude 17.6 and with an average impact velocity
could
generate an explosion with energy greater than 100,000 MT. This
corresponded
to a value on the Palermo technical scale of -1.85, already a
noteworthy
value. Moreover, there were another 14 VIs identified with
possible impacts
between 2014 and 2056. At about the same time Steve Chesley
reported that
the JPL Sentry automatic collision monitoring system, which is in
continuing
development, also autonomously detected the impacting solutions
of VK5
reported by Milani. This NEA was in the Category 1 class on both
the Torino
Scale and the Palermo Scale, although everyone recognized that
these
calculations were based on a short arc, and that new astrometry
would almost
surely resolve the uncertainties within a few days.
Milani requested that the WGNEO activate its technical review
process for
2001VK5, which I did on 19 November, writing "I concur with
your decision to
submit this information to the IAU WGNEO Technical Committee for
review at
this time, since it has such a complicated orbit that it is
especially
important to obtain independent verification of the virtual
impactor
possibilities. In the meantime the asteroid remains visible in a
dark sky,
and I have no doubt that additional data will be coming in. This
parallel
request for both new observational data and a peer check of the
calculations
is in my opinion entirely appropriate. Depending on the events of
the next
72 hours the IAU may (or may not) wish to make a formal statement
. . . I
personally urge that this be kept as low-key as possible until
additional
data are acquired that may resolve the risk of impact."
The members of the IAU Technical Review Team (Don Yeomans, Paul
Chodas,
Steve Chesley, Karri Muinonen, Giovanni Valsecchi) did an
excellent job of
providing independent analysis of the orbit, confirming (using
different
methods) Milani's calculations of the probability of impact. At
the same
time, with the active cooperation of both the Minor Planet Center
(Brian
Marsden) and the Spaceguard Foundation Central Node (Andrea
Carusi),
additional observations were obtained and given immediately to
the orbit
calculators. By 21 November (the end of the 72 hour period for
the IAU
Technical Review), the possibility of an impact in 2011 had been
eliminated
by new data, but there still remained several VIs in the out
years. In view
of the continuing input of data, we decided to defer any
announcement from
the IAU until after the USA Thanksgiving holiday. Milani posted
the current
information on his website but also did not make any public
announcement.
By 25 November, orbit calculations based on new observations had
effectively
eliminated all of the virtual impactor possibilities, and 2001VK5
had
dropped back to a category zero in the Torino impact scale.
I believe that this case is an example of the proper functioning
of the IAU
Technical Review of orbital calculations and of the efforts of
the MPC and
SGF to solicit and coordinate additional observations of a
high-priority
target. The fact that this international collaboration was
carried out
without publicity provides a model for future cases of short-arc
NEAs that
are initially flagged as potential impactors but that drop back
into the
background as more observations are accumulated. I expect there
will be many
more such examples as new NEAs continue to be discovered at a
high rate.
David Morrison
Chair, IAU WGNEO
=================================
NEOS AT THE DPS, NOVEMBER 2001
Several interesting research results dealing with NEOs were
presented at the
33rd meeting of the Division for Planetary Sciences (DPS) of the
American
Astronomical Society (AAS), held in New Orleans at the end of
November.
Following are a few highlights that seemed interesting to me. The
material
presented below is a combination of the published abstract and
some
introductory comments that I have added.
David Morrison
===============================
The following four abstracts describe results from the successful
flyby of
Comet Borrelly by the NASA Deep Space 1 spacecraft. The imaging
at
resolutions as good as 60 meters provides the best look at a
comet nucleus
since the Giotto photos of Comet Halley. In fact, a combination
of higher
resolution and lower dust opacity means that both the surface of
the comet
and its focused gas jets are seen better than for any previous
comet. The
nucleus is 5 km long and substantially elongated, with a rotation
period of
25 hours. Its albedo (reflectivity) is extremely low, about 3%,
similar to
dark charcoal or coal. The surface is relatively smooth but shows
variations
in albedo.
----------------------------------------------------------
[26.01] The Deep Space One Encounter with the Comet Borrelly
R. M. Nelson, M. D. Rayman, P. Varghese, D. H. Lehman (Jet
Propulsion
Laboratory)
On September 22, 2001 NASA's Deep Space One spacecraft flew by
the Comet
Borrelly at a distance of 2200 km. The spacecraft instrument
package
included a Miniature Integrated Camera Spectrometer (MICAS), a
Plasma
Experiment for Planetary Exploration (PEPE), and numerous
diagnostic
instruments, intended to monitor the status of ion drive which
propelled the
spacecraft (IDS). All the instruments returned high quality
science data on
the Comet. This session will present the first results from the
flyby to the
scientific community.
--------------------------------------
[26.02] Observations of Comet 19P/Borrelly from the Miniature
Integrated
Camera and
Spectrometer (MICAS) aboard Deep Space 1 (DS1)
L. A. Soderblom (USGS), D. C. Boice (SwRI), D. T. Britt (U Tenn),
R. H.
Brown (U Az), B. J. Buratti, M. D. Hicks, R. M. Nelson (JPL), J.
Oberst
(DLR), B. R. Sandel (U Az), S. A. Stern (SwRI), N. Thomas (MPAE),
R. V.
Yelle (NAU)
Images from the DS1 MICAS CCD camera reveal in three dimensions,
the complex
characteristics of Borrelly's nucleus, coma, and jets. The images
acquired
during the last 2 hours of the approach, as the nucleus became
resolved and
grew to roughly 150 pixels in length, provide stereo coverage of
both the
nucleus and inner coma over a wide range of phase angle and
exposure time.
The principal structure in the coma is a sunward-pointed
collimated jet that
is also visible in ground-based images. This jet is canted about
30 degrees
off the sun line and appears to be roughly aligned with the local
vertical
at the surface from where it originates. Long-exposure images
reveal details
of the structure of the inner coma. They show the jet, visible at
long
range, to be composed of at least three discrete components whose
locations
evidently correspond to specific surface features. The elongated
nucleus
exhibits topographically distinct terrains and strong albedo
variegations
(of at least a factor of 2). The jets emanate from within the
brighter
smoother rolling plains. A consistent model is that the main jets
are
co-aligned with the rotation axis of the nucleus and issue from
regions on
the plains that are currently in constant sunlight. The other
major terrain
is a rough unit that is darker than the average, includes even
darker
isolated spots, and appears as a jumbled topography. Other
surface features
include parallel ridges, crater-like depressions, numerous narrow
dark
fracture-like features, and areas of mottled albedo. However no
small fresh
impact craters are evident attesting to a geologically young,
actively
evolving surface.
----------------------------------------
[28.03] The Geology of Comet 19P/Borrelly
D. T. Britt (University of Tennessee), D. C. Boice (SwRI), R. M.
Nelson
(JPL), L. A. Soderblom (USGS), N. Thomas (MPAE)
The Deep Space One spacecraft returned MICAS images of the Comet
19P/Borrelly with surface resolutions as good as 60 meters per
pixel. These
data converted the nucleus of Borrelly from an astronomical
object, obscured
by its coma of gas and dust, to a geological object with striking
surface
morphology and processes. The surface is dominated by two major
units. The
Smooth Rolling Plains (SRP) unit shows higher than average
albedo, is
smoother than average, and is associated with the surface
locations of
Borrelly's active jets. The smooth terrain and higher albedo
appear
associated with active resurfacing processes from dust ejection.
Away from
the active jets the surface is darker, rougher, and exhibits
mottled albedo
features. This Rugged Terrain unit may represent older surface
material.
Along the terminator there are 4 parallel ridges that are
oriented normal to
the long axis of the comet. On the sun side are a complex set of
fractures
near what appears the narrowest part of the comet. Several
crater-like
depressions are visible, but the surface generally lacks abundant
craters.
Albedo values vary by at least a factor of two across the
surface.
------------------------------------
[28.04] Photometry and Surface Physical Properties of Comet
19P/Borrelly
B. J. Buratti (JPL), L. A. Soderblom (USGS), D. T. Britt (U.
Tenn.), M. D.
Hicks (JPL), N. Thomas (Max Planck Inst. ), J. Oberst (DLR), R.
H. Brown (U.
Ariz.), R. M. Nelson, J. A. Mosher (JPL), J. K. Hillier (Grays
Harbor
College)
The successful Deep Space 1 flyby of Comet P/19 Borrelly offers
an
unprecedented opportunity to perform disk-resolved photometry and
photometric modeling of a comet's nucleus. The flyby occurred at
a favorable
ground-based apparition, enabling concomitant telescopic
observations that
provided both the "big picture" in time and space and
observations at
photometric viewing geometries not attained by the spacecraft.
The solar
phase angle of the encounter period changed from 87 to 52 degrees
over a
period of 1.5 hours; this range is ideal for determining the
macroscopic
roughness of the comet's surface. The microphysical texture of
the surface
is best determined by ground based observations at aphelion and
near
opposition. The combination of both disk resolved measurements
from DS1 and
disk integrated measurements from both DS1 and the ground permits
a
constrained set of photometric parameters to be derived.
Preliminary
analysis of the global geometric albedo yields a value at V
wavelengths (550
nm) between 0.031 +/- 0.005 (for a Mathilde-type solar phase
curve at phase
angles less than 10 degrees) and 0.042 +/- 0.005 (for an average
C-type
phase curve). Albedo variegations of at least a factor of two
exist on
Borrelly's surface: Its light curve amplitude of nearly a
magnitude may thus
not be due to shape alone. The image resolution of ~ 60 m allows
mapping of
albedo variegations in terms of active jet morphology.
==================================
The following two papers deal with the NASA NEO Program Office
and with new
software that can provide an automated search for future impact
possibilities for NEAs.
----------------------------------------------
[41.07] NASA's Near-Earth Object Program Office
D.K. Yeomans, R.C. Baalke, A.B. Chamberlin, S.R. Chesley, P.W.
Chodas, J.D.
Giorgini, M.S. Keesey (JPL/Caltech)
In early 1999, NASA established its Near-Earth Object Program
Office at the
Jet Propulsion Laboratory, with the stated objectives to: ·
Facilitate
communications within the observing community and between the
community and
the public with respect to any potentially hazardous objects. ·
Establish
and maintain a catalog of Near-Earth Objects (NEOs) and provide
information
on their future close Earth approaches and Earth impact
probabilities. ·
Help coordinate ground-based observations in order to complete
the
Spaceguard Goal of discovering 90% of the Near-Earth Asteroids
(NEAs) larger
than one kilometer within a ten year period. · Support NASA
Headquarters in
coordinating with other government agencies and with foreign
governments and
international organizations on NEO issues. · Develop and support
a strategy
and plan for the scientific exploration of NEOs including their
discovery,
recovery, ephemerides, characterization, in-situ investigations,
and
resource potential. Significant progress has been made on all of
these
objectives. An award winning interactive NEO web site has been
established
(http://neo.jpl.nasa.gov/)
to communicate information to the scientific
community and public. An automatic update process (Sentry) has
been
established for all NEOs. As new astrometric data become
available for a
particular NEO, its orbit is automatically updated and future
close Earth
approach circumstances determined - including impact
probabilities when
appropriate. At timely intervals, metrics are generated and
displayed on the
web site to track the contributions of each NASA supported search
site
toward meeting the Spaceguard Goal. Initial efforts to coordinate
the
nightly search for NEAs within the United States have been
undertaken. In an
effort to facilitate the coordination of NEO activities on an
international
scale, fruitful interactions have taken place with personnel of
the British
Task Force, the Spaceguard Foundation, the Japanese Spaceguard
Foundation
and the international Organization for Economic Cooperation and
Development
(OECD).
--------------------------------------------
[41.08] Sentry: An Automated Close Approach Monitoring System for
Near-Earth
Objects
A.B. Chamberlin, S.R. Chesley, P.W. Chodas, J.D. Giorgini, M.S.
Keesey, R.N.
Wimberly, D.K. Yeomans (JPL/Caltech)
In response to international concern about potential asteroid
impacts on
Earth, NASA's Near-Earth Object (NEO) Program Office has
implemented a new
system called ``Sentry'' to automatically update the orbits of
all NEOs on a
daily basis and compute Earth close approaches up to 100 years
into the
future. Results are published on our web site (http://neo.jpl.nasa.gov/) and
updated orbits and ephemerides made available via the JPL
Horizons ephemeris
service (http://ssd.jpl.nasa.gov/horizons.html).
Sentry collects new and
revised astrometric observations from the Minor Planet Center
(MPC) via
their electronic circulars (MPECs) in near real time as well as
radar and
optical astrometry sent directly from observers. NEO discoveries
and
identifications are detected in MPECs and processed
appropriately. In
addition to these daily updates, Sentry synchronizes with each
monthly batch
of MPC astrometry and automatically updates all NEO observation
files. Daily
and monthly processing of NEO astrometry is managed using a
queuing system
which allows for manual intervention of selected NEOs without
interfering
with the automatic system. At the heart of Sentry is a fully
automatic orbit
determination program which handles outlier rejection and ensures
convergence in the new solution. Updated orbital elements and
their
covariances are published via Horizons and our NEO web site,
typically
within 24 hours. A new version of Horizons, in development, will
allow
computation of ephemeris uncertainties using covariance data. The
positions
of NEOs with updated orbits are numerically integrated up to 100
years into
the future and each close approach to any perturbing body in our
dynamic
model (all planets, Moon, Ceres, Pallas, Vesta) is recorded.
Significant
approaches are flagged for extended analysis including Monte
Carlo studies.
Results, such as minimum encounter distances and future Earth
impact
probabilities, are published on our NEO web site.
=====================================
The following paper discusses the internal structure of NEAs and
implications for their break-up during atmospheric entry and
impact with the
surface.
-------------------------------------
[41.05] The Role of Asteroid Strength in Impact Damage
J.G. Hills, M.P. Goda (Los Alamos National Lab)
The fragmentation and dispersal of an asteroid in the atmosphere
help
determine the damage it can cause (Hills and Goda, 1993,
Astronomical J.
105, 1114-1144). Large asteroids are suspected to be rubble piles
with
little overall strength. This lack of strength causes them to
break up
higher in the atmosphere than would be the case if they had the
same
material strength as normal meteorites. The higher elevation
breakup causes
them to spread apart more at a given elevation in the atmosphere,
so less of
their energy is available for ground impact. We made computer
simulations of
such dispersal using asteroids of normal strength and those with
much
reduced strength to see if the more fragmented asteroids produce
less
damage. We find that these differences are much greater for irons
than for
stones, which is not surprising given the greater material
strength of the
irons. Irons with radii less than about 20 meters lose most of
their energy
before they reach sea level if they are of normal strength. If
they are
rubble piles, they produce little ground impact damage unless
their radii
exceed 70 meters. Iron asteroids have to have radii above these
critical
values to allow them to produce significant craters on land and
tsunami in
water. If the radius of an iron asteroids exceeds 200 meters, the
size of
the crater it produces is nearly independent of its material
strength.
Solid-stone asteroids with radii greater than about 100 meters
produce
significant craters. This critical limit is only about 20% larger
for
rubble-pile stone asteroids. Blast damage from stony asteroids is
not very
sensitive to their strength. Small iron asteroids, with radii
less than
about 20 meters, produce more blast damage if they are solid,
because their
energy is dissipated lower in the atmosphere. If their radii
exceed this
value, the weaker asteroid produces more blast damage than the
stronger one
because the stronger one loses less of its energy in the
atmosphere and more
of it on ground impact.
==================================
One of the most exciting recent areas of asteroid research is
derived from
the discovery of asteroid satellites. Observations of a satellite
allow
determination of the mass and density of the asteroid, and thus
inferences
about its internal structure and composition. The discovery of
asteroid
satellites has also stimulated dynamical models to try to
understand how
these satellites have formed. Bill Merline of Southwest Research
Institute
gave an invited talk on asteroid satellites. It is interesting
that small
NEAs as well as larger main belt asteroids have satellites. Four
NEA
satellites have been found so far, mostly from radar
observations,
suggesting that perhaps 20% have satellites. In addition to the
review,
Merline gave the following research paper. Several additional
papers (not
included here) dealt with the radar observations.
---------------------------------------
[52.01] Search for Asteroid Satellites
W.J. Merline (SwRI), L.M. Close (U. Arizona), F. Menard (LAOG,
Obs.
Grenoble, France), C. Dumas (JPL), C.R. Chapman, D.C. Slater
(SwRI)
We report on the recent progress of our comprehensive search for
satellites
of asteroids. In 1998, we began our survey using newly developed
technologies in adaptive optics to explore the close environs of
several
hundred main-belt asteroids. Adaptive optics (AO) removes the
blurring
caused by the Earth's atmosphere and allows diffraction-limited
imaging in
the near-IR (J-,H-,K'-bands) at the world's largest telescopes.
Angular
resolutions as high as 0.04 arcsec are possible. We have employed
the
excellent facilities at the Canada-France-Hawaii Telescope, the
W.M. Keck II
telescope, and the new Gemini North 8m telescope. Each of these
facilities
provides unique capabilities and are each complementary to the
other. So far
we have discovered or recovered a half-dozen small moons or
double asteroids
by this AO-assisted direct-imaging technique. Our sample now
exceeds 300
main-belt targets, and we have expanded the survey to include
near-Earth and
Trojan asteroids. Other groups are using AO, direct HST imaging,
direct
ground-based imaging, advanced lightcurve analysis, and radar
techniques to
further sample these populations, as well as the Kuiper Belt. Our
results
show that the frequency of binary asteroids (at least to our
detection
limits) is rather small in the main belt, possibly a few percent.
Frequencies among other populations, such as the NEAs, are seen
to be much
higher. We also find that although there are similarities among
the detected
systems, there are also significant differences. Thus, it is
likely that
several different formation mechanisms will be required to
explain the
observed systems. All of the proposed mechanisms for formation
involve
collisions of one type or another (physical or gravitational).
Study of
these systems will provide significant insight to the collisional
history
and evolution of these asteroid populations. Further, the
presence of a
companion allows accurate determination of the density of the
primary, and
thus yields vital information about the composition and
structure. Already,
we have seen that most asteroids are underdense compared with
their likely
meteorite counterparts, and thus we must invoke significant empty
space or
macroporosity in their structure.
==============================
Several papers discussed the Spaceguard Survey, the population of
NEAs, and
the current rate of progress toward meeting the Spaceguard Goal
of finding
90% of the NEAs larger than 1 km by 2008. The consensus is
growing that
there are roughly 1000 NEAs brighter than absolute magnitude
H=18. For a
nominal albedo, H=18 is equivalent to a diameter of 1 km, but
this will not
be true for individual objects, depending on their surface
reflectivity. The
specific model presented by Morbidelli and his colleagues gives
an NEA
population of 834 larger than 1 km and 963 brighter than
magnitude 18. It
seems increasingly clear that the current Spaceguard Survey,
although it has
by now discovered more than half the NEAs brighter than H=18,
does not reach
deep enough (faint enough) to achieve the Spaceguard Goal of 90%
discovery
by 2008. For example, the current magnitude limit for LINEAR is
about 19,
while the models suggest that it will be necessary to survey down
to at
lesst magnitude 20 to achieve this goal. Incidentally, it was
reported that
LINEAR has by now effectively surveyed 10 cubic astronomical
units for NEAs
down to H=18.
--------------------------------------
[54.07] Earth and Space-based NEO Survey Simulations: Prospects
for
Achieving the Spaceguard Goal
R. Jedicke (Lunar & Planetary Laboratory), A. Morbidelli
(Obs. de la Cote
d'Azur), T. Spahr (Smithsonian Astrophysical Observatory), J-M.
Petit (Obs.
de la Cote d'Azur), B. Bottke (Southwest Research Institute)
Using our model of the debiased orbital and absolute magnitude
distribution
of Near Earth Objects (NEO) (Bottke et al. 2001, Icarus,
accepted), we have
simulated the efficiency of various surveying strategies. To
check the
fidelity of our model and simulation we have calculated the
number of NEOs
with H<18 that the Catalina Sky Survey (CSS) should have
detected in a
nine-month observing period. The CSS detected 38 NEOs (2 Atens,
21 Apollos
15 Amors) while we predict that they should have found 28±5 NEOs
(1.5±1.2
Atens, 17.3±4.5 Apollos, 9.1±3.3 Amors). Taking into
consideration the
difficulties in parameterizing the CSS asteroid rejection system,
we believe
our model is reliable and that it can be used to simulate the
discovery
efficiency of existing and virtual surveys. Our main results are
the
following: (i) the LINEAR-like survey to a limiting magnitude of
18.5 can
not fulfill the NASA goal of finding 90% of NEOs with H<18 by
2008. Only
60-70% of these bodies will be found (current completeness being
~45%). (ii)
the system performance is not much better if restricted to the
sub-categories of NEOs with the largest collision probability
with the Earth
or the smallest MOIDs (iii) a LINEAR-like survey with limiting
magnitude
~21.5 could fulfill the NASA goal while the proposed LSST survey
will be
extremely effective. (iv) the determining factor in a survey's
success is
its limiting magnitude. The latitude of the observatory and the
`NEO rate
cut' do not significantly reduce the overall performance. (v) a
dedicated
survey from a satellite orbiting the Sun from the distance of
Mercury would
be extremely effective, especially for discovering NEOs with the
smallest
MOID. Even a survey with a limiting magnitude equal to 18.5 would
discover
90% of the NEOs in just a few years.
----------------------------------------
[54.08] Detection Efficiency of LINEAR
J. B. Evans, G. H. Stokes, H. E. M. Viggh, J. S. Stuart (MIT
Lincoln
Laboratory)
The Lincoln Near Earth Asteroid Research (LINEAR) program has
applied
electro-optical technology developed for Air Force Space
Surveillance
applications to the problem of discovering Near Earth Asteroids
(NEAs) and
comets. LINEAR, which started full operations in March of 1998,
has
discovered through July of 2001, 667 NEAs, 35 unusual objects,
and 64
comets. Currently, LINEAR is contributing ~70% of the world-wide
NEA
discovery rate. This paper details preliminary studies into the
detection
efficiency of the LINEAR system. The detection efficiency of the
system is
computed for individual nights when the region of sky searched
has a
statistically significant number of candidate moving objects for
detection.
Limiting visual magnitudes are obtained from these nights, and
the
information garnered allows for the estimation of the limiting
visual
magnitudes for the remainder of the nights. An accurate measure
of the
limiting magnitude is essential to characterizing a search
system's
capability.
----------------------------------------
[54.09] The NEA Population and the Spaceguard Goal
J.S. Stuart (MIT)
Three years of search data from the Lincoln Near-Earth Asteroid
Research
(LINEAR) project allow us to estimate the size and shape of the
near-Earth
asteroid population. To calibrate the limiting magnitude of the
LINEAR
search, we restrict ourselves to nights with stable weather. We
are left
with 375,000 square degrees of sky coverage and over 1300 NEA
detections. A
simulation of discovery circumstances for the range of absolute
magnitude
and orbital parameters of the detected asteroids is used to
determine the
detection probabilities. From these detection probabilities, the
biases of
the survey are estimated, allowing us to calculate the total
population from
that which is observed. We previously presented (DPS2000) a
population
estimate that used an assumption for the shape of the population
over the
semi-major axis and eccentricity dimensions. In this work we
remove that
assumption and derive estimates over absolute magnitude (H),
semi-major
axis, eccentricity, and inclination. As in the previously
presented work, we
find that the NEAs are more highly inclined than the currently
known
population and more highly inclined than other estimates. The
number of NEAs
with H<18 is found to be in the range 1150 to 1400. We also
investigate the
requirements for a search system to complete the Spaceguard goal
of
discovering 90% of the 1 km NEAs by 2008, assuming that the real
population
is similar to the model derived here. Since the albedo
distribution of the
NEAs is currently unknown, we cannot fully evaluate progress
toward the
Spaceguard goal. However, if we assume that H=18 corresponds to a
diameter
of 1 km, then a single telescope similar to LINEAR requires 40
years to
reach 90% completeness. If the albedo distribution of the
asteroids is such
that 1 km corresponds to H=17.5, then 30 years are required. The
opposite
case of low average albedo, setting the 1 km target at H=18.5,
requires 60
years. A coordinated collection of telescopes capable of
searching the
entire available sky each lunation to limiting magnitude V ~ 20.5
is
necessary to complete the Spaceguard goal in 10 years from system
inception,
assuming that H=18 corresponds to 1 km.
----------------------------------------
[54.06] NEO Albedo Distribution and Impact Hazards
A. Morbidelli (Observatory of Nice, France), W.F. Bottke (South
West
Research Institute, Boulder, Co.), R. Jedicke (Lunar Planetary
Laboratory,
Tucson, Az.), P. Michel (Observatory of Nice, France), E.F.
Tedesco
(TerraSystems Inc., Lee, NH)
Our NEO orbital-magnitude distribution model (Bottke et al.,
2001, Icarus,
in press) relies on 5 main intermediate sources for the Near
Earth Object
population: the nu6 resonance, the 3:1 resonance, the outer
portion of the
main belt (I.E., 2.8-3.5 AU), the Mars-crossing population
adjacent to the
main belt, and the Jupiter family comet population. The model
establishes
the relative contribution of these sources to the NEO population,
in each
region of the NEO orbital space. Therefore, by computing the
albedo
distribution of the bodies in/close to each source, we can deduce
the albedo
distribution of the NEO population, as a function of their
orbital location.
An important caveat is that the albedo distribution of main belt
asteroids
may change with the absolute magnitude, because asteroid families
and
background populations have different albedo and magnitude
distributions. In
our model we extrapolate the observed absolute magnitude
distributions of
the families up to some threshold value Ht, beyond which we
assume that the
families magnitude distribution is background-like. We find that
Ht=15
provides the best match to (I) the color vs. heliocentric
distance
distribution observed by the SLOAN survey and with (II) the
observed albedo
distribution of NEOs. Our model predicts that the debiased ratio
between
dark and bright (albedo smaller or larger than 0.089) NEOs with
diameter
larger than 1km is 0.8 . We estimate that the total number of
NEOs larger
than a kilometer is 834 which, compared to the total number of
NEOs with
H<18 (963), shows that the usually assumed conversion
H=18~<=>~D=1km is
slightly pessimistic, on average. The right statistical
correspondence
should be H=17.82~<=>~D=1km. Combining our orbital
distribution model with
the new albedo distribution model, and assuming that the density
of bright
and dark bodies is 2.7 and 1.3 g/cm3, respectively, we estimate
that the
Earth should undergo a 1000 megatons collision every 64,000
years. The NEOs
discovered so far carry only 18% of this collision probability.
=====================================
Finally, I note that considerable progress has been made lately
in
reconciling telescopic spectra of asteroids with the colors
measured in the
laboratory for meteorites. We are beginning to understand the
ways in which
exposure to space ("space weathering") changes over
time the spectra of
materials on asteroid surfaces.
--------------------------------------
[59.06] Size Dependence of Near-Earth Asteroid Spectral
Properties: A
Comparison with Space Weathering Models
R. P. Binzel (Obs. Paris), S. J. Bus (U. Hawaii), T. H. Burbine
(NMNH), L.
E. Malcom (Caltech)
The availability of a self-consistent set of visible wavelength
CCD spectra
for more than 1400 asteroids (Bus 1999, Ph. D. Thesis; Bus and
Binzel,
submitted) that includes measurements for more than 100
near-Earth objects
(Binzel et al., in preparation), provides the basis for an
analysis of size
dependent spectral properties. Near-Earth objects, by virtue of
their
proximity, provide the opportunity for spectral measurements of
objects at
sizes below 100 m. By analyzing the spectral properties of
near-Earth
objects in conjunction with those for > 100 km main-belt
asteroids, we have
the ability to identify spectral trends for objects spanning more
than 3
orders magnitude in size. Collisional lifetimes of asteroids are
proportional to their size, since larger asteroids are less
likely to be
disrupted by collisions. Smaller asteroids have shorter
collisional
lifetimes. Thus smaller asteroids have younger ages than large
asteroids and
can be expected, on average, to have younger surfaces. Space
weathering
models that alter an asteroid's surface over time (e.g. Pieters
et al. 2000,
Met. Plan. Sci. 35, 1101; Sasaki et al. 2001, Nature 419, 555)
would predict
that smaller asteroids would be the less effected by weathering
than larger
objects. In this paper we examine the statistical significance of
size
dependent trends in asteroid spectral properties and compare
significant
trends in the data with the what is predictable based on space
weathering
models. The ability of space weathering models to give results
consistent
with the data is a key element in evaluating their validity.
+++++++++++++++++++++++++++++++++++++++++++
NEO News is an informal compilation of news and opinion dealing
with Near
Earth Objects (NEOs) and their impacts. These opinions are
the
responsibility of the individual authors and do not represent the
positions
of NASA, the International Astronomical Union, or any other
organization.
To subscribe (or unsubscribe) contact dmorrison@arc.nasa.gov.
For
additional information, please see the website: http://impact.arc.nasa.gov.
If anyone wishes to copy or redistribute original material from
these notes,
fully or in part, please include this disclaimer.
==============
(4) WEIRED GEMINIDS
>From NASA Science News, 7 December 2001
http://science.nasa.gov/headlines/y2001/ast07dec_1.htm?list20392
What are the Geminid meteors? Scientists aren't sure. Perhaps
chips off an
exotic asteroid or dust from an extinct comet. In either case,
they'll soon
be here.
Dec. 7, 2001: When the thrilling 2001 Leonid meteor storm finally
subsided
last month, many first-time meteor watchers were asking the same
question:
"When's the next meteor shower!?"
The answer is "now." Today Earth is entering the
outskirts of a dusty debris
cloud shed by a mysterious object named 3200 Phaethon. It's the
beginning of
the annual Geminid meteor shower, which peaks this year on Dec.
13th and
14th.
The two-week long Geminid shower is barely a trickle at the
moment -- only 5
to 10 meteors per hour. But soon it will intensify ten-fold or
more.
You can catch the main event beginning just after sunset on
Thursday, Dec.
13th.
"When the Sun goes down on Thursday," says Bill Cooke
of the NASA Marshall
Space Flight Center, "Gemini will be low but rising over the
eastern horizon
[as viewed from mid-northern latitudes]. You won't see many
meteors then,
but the ones you do will likely be beautiful Earthgrazers"
-- that is,
disintegrating meteoroids that fly over the horizon nearly
parallel to the
atmosphere. Earthgrazers are long, bright and vivid. A remarkable
sight.
"After an hour or so of watching for Earthgrazers, you might
want to go back
inside for a few hours and warm up," adds Cooke. Meanwhile,
Gemini will
continue to climb higher in the sky. "Around midnight go
back outside," he
suggests. "Gemini will lie almost directly overhead. From
midnight until
dawn on Friday, Dec. 14th, you could spot as many as 100 shooting
stars per
hour."
Cooke's suggestions are correct for observers in any time zone of
the United
States or Europe.
Nowadays the Geminids are generally regarded as one of the best
annual
meteor showers. But it wasn't always so. Before the mid-1800's
there were no
Geminids, or at least not enough of them to attract attention.
The first
Geminid shower suddenly appeared in 1862, surprising sky watchers
who saw 15
or so shooting stars each hour.
Astronomers immediately began looking for a comet. Most meteor
showers
result from debris that that boils off a comet when it passes
close to the
Sun. When Earth passes through the debris, we see a meteor
shower.
For more than a century astronomers searched in vain for the
parent of the
Geminids. Finally, in 1983, NASA's Infra-Red Astronomy Satellite
(IRAS)
spotted something. It was several-km wide and moved in much the
same orbit
as the Geminid meteoroids. Scientists named it 3200 Phaethon.
But rather than solving the puzzle of the Geminids parentage, the
IRAS
discovery simply deepened the mystery. Why? Because Phaethon
appears to be
an asteroid. Indeed it's cataloged as a potentially-hazardous one
that skims
by Earth's orbit only 8 times farther away than the Moon.
Asteroids that
spew debris into space like a comet are rare indeed, so
astronomers were
more baffled than ever.
This unusual asteroid, known as Elst-Pizarro, briefly sprouted a
tail in
1996 after, perhaps, a collision with another object in the
asteroid belt.
Is this what happened to 3200 Phaethon long ago? Brian Marsden of
the Minor
Planet Center discusses the possibility in a Science@NASA article about last
year's Geminids
(http://science.msfc.nasa.gov/headlines/y2000/ast08dec_1.htm).
Since then many sky watchers have come to regard the Geminids as
a "weird"
meteor shower -- the only one caused by an asteroid. But maybe,
says Cooke,
it's not so weird after all. "I don't think the Geminids
come from an
asteroid. They're cometary ... just like all the other meteor
showers. 3200
Phaethon is indeed the parent, but it's an extinct or dormant
comet."
According to Cooke, Phaethon probably looked much like other
comets many
centuries ago, with a fuzzy head and a glowing dusty tail. But
this one was
doomed to rapid extinction by its short-period sungrazing orbit.
Every one
and a half years Phaethon plunges sunward from the asteroid belt
and swings
by the Sun at a distance of 0.14 astronomical units -- closer
even than the
planet Mercury. Such near encounters with the Sun would have
cooked
Phaethon, vaporizing its ices and leaving behind a shell of
asteroid-like
dust and rock.
Such over-cooked comets may be abundant, says Mike A'Hearn (Univ.
of
Maryland), the principal investigator of NASA's Deep Impact
mission.
"Dynamical studies suggest that perhaps a few percent to 50%
of all
near-Earth objects are dormant or extinct comets masquerading as
asteroids."
>From a distance there's no definitive way to tell the two
apart. "Both
comets and main belt asteroids are very dark," says Lucy
McFadden (Univ. of
Maryland), a member of the Deep Impact science team. "And we
don't know of
any robust chemical or spectral signature to absolutely identify
a comet's
nucleus." Indeed, she says, "even if we were to fly to
Phaethon we might not
be able to tell whether it is an extinct comet" without
somehow looking
beneath its crust.
That's exactly what the Deep Impact spacecraft will do to Comet
Tempel 1
when it travels there in 2005 and excavates a crater by dropping
a 350 kg
impactor onto the comet. A goal of the mission is to learn what
the crusts
of comets are made of and what lies beneath them. "Perhaps
in a few years we
will feel more confident of the chemical signature of comet
nuclei," adds
McFadden.
Meanwhile 3200 Phaethon is likely to remain a puzzle. Are the
Geminids
caused by old dust from an extinct comet or chips off an exotic
asteroid? No
one knows. But don't let that stop you from heading outdoors on
Dec. 13th
and 14th. This is a mystery best pondered under dark skies ...
with a flurry
of beautiful Geminids soaring overhead!
=============
(5) NASA TO DISCUSS LEONIDS, MARS AND EARLY EARTH AT AGU
>From Ron Baalke <baalke@jpl.nasa.gov>
Dec. 7, 2001
Kathy Burton
NASA Ames Research Center, Moffett Field, Calif.
(Phone: 650/604-1731 or 604-9000)
E-mail:kburton@mail.arc.nasa.gov
AGU Moscone Center press room, San Francisco
(Phone: 415/905-1007, general AGU information)
NOTE TO EDITORS: 01-98AR
NASA TO DISCUSS LEONIDS, MARS AND EARLY EARTH AT AGU
The latest models of meteors and meteoroid streams, the first
science
results from the November Leonid meteor storm and the latest Mars
research
will be presented at the fall American Geophysical Union (AGU)
meeting Dec.
10 through 14 at the Moscone Convention Center in San Francisco.
Dr. Peter Jenniskens, principal investigator of NASA's Leonid
"MAC" mission,
which tracked the meteors, will present the latest data at a
special
session, "The 2001 and 2002 Leonid Meteor Storms," at
the AGU meeting at
1:30 p.m. PST, Dec. 11 in the Moscone Center's room MC 120.
Jenniskens,
together with scientists from the Scripps Institute and Cornell
University,
will discuss first results from the last two Leonid meteor
events, including
airborne meteor and meteor train observations, comet dust
composition, the
fate of organic matter at the time of the origin of life, and the
physics
and chemistry of the Earth's upper atmosphere. Approximately 30
NASA Ames
scientists will participate in a wide range of space and
planetary science
presentations at the AGU meeting, either as session chairs,
invited
speakers, lead authors or 'poster session' presenters.
There will be more than 14 AGU presentations dealing with NASA's
latest Mars
research, with discussions ranging from the accuracy of Mars
climate models
to what currently is known about the red planet's surface
geology. Ames
scientists Dr Robert Haberle and Dr Anthony Colaprete will
present work
about Mars' climate on Wednesday and Thursday. The Mars Global
Surveyor
(MGS) mission has provided a wealth of new data bearing directly
on Mars'
climate. Colaprete, Haberle and others will compare the most
recent MGS data
with data from the NASA Ames Mars General Circulation Model at
separate
sessions scheduled for Dec. 12 at 8:30 a.m. (MC 308) and 3:30
p.m. PST (MC Hall D) and Dec. 13 at 8:30 a.m. PST (MC Hall D).
Ames climate
researcher Dr. Jeffery Hollingsworth will discuss Mars'
atmospheric
circulation in the Hellas impact basin, comparing model
simulations with
recently acquired MGS data on Dec. 12 at 3:55 p.m. PST in MC 301.
Also on the Mars theme, Ames' Dr. Nathalie Cabrol will present a
new paper,
"From Gullies to Glaciers: A Continuum of Evidence
Supporting A Recent
Climate Change on Mars," on Dec. 10 at 4:20 p.m. PST in MC
131. Based on
the recent discovery of pristine martian gullies by the Mars
Global
Surveyor, Cabrol will present a continuum of evidence that
supports a recent
climate change on Mars, signaling a more recent hydrologically
active Mars
than scientists had thought previously. Her talk is part of
the "New
Paradigms for the Water Cycle on Mars I" session that begins
at 1:30 p.m.
PST.
Conditions on early Earth are another topic well represented by
Ames
scientists. Dr. Kevin Zahnle of Ames will deliver two review
talks
discussing the earliest atmosphere of the Earth. He will present
"Hot Steam,
Hard Rain and Icy Wastes in the Hadean" on Dec. 11 at 8:30
a.m. PST in MC
308 at the 'Follow the Water' session and "The Hadean
Atmosphere (When
Impacts Ruled the Earth)" on Dec. 14 at 11:10 a.m. PST in MC
134 in the
'Origin and Early Evolution of the Earth' session.
The 'Follow the Water' session focuses on the search for
habitable
environments in the solar system. It will be co-chaired by
Dr. Michael
Meyer, senior scientist for astrobiology in the Office of Space
Science at
NASA Headquarters and by Dr. Jack Farmer, principal investigator
of the
Arizona State University research team at the NASA Astrobiology
Institute.
Ames researchers Dr. Linda Jahnke and Kenneth Cullings will
reconstruct the
biomarker record of early Earth in a poster sesion (B22D-0184) at
1:30 p.m
PST on Dec. 11 in MC Hall D.
More information about the AGU fall meeting is available on the
Internet at:
http://www.agu.org/meetings/fm01top.html
For further information about Ames' participation in the AGU, go
to the AGU
website and search the 'Meeting at a Glance' section using the
researcher's
e-mail address. You also can use the keyword 'arc.nasa.gov'
to locate
abstracts and session information.
To arrange interviews at AGU, please contact Harvey Leifert in
the AGU Press
Room, MC 111, 415/905-1007. Reporters also may arrange an
interview at AGU
by using the AGU message board located outside Moscone's main
exhibition
hall.
The AGU is a worldwide organization comprising over 39,000
scientists in
Earth and space science, publishing more than a dozen
peer-reviewed journals
annually and holding regular science meetings.
=============
(6) PLANETARY SCIENCE AT THE AGU MEETING
>From Michael Paine <mpaine@tpgi.com.au>
Dear Benny
There is once again a smorgasbord of NEO-related items at the
annual meeting
of the American Geophysical Union http://www.agu.org/meetings/fm01top.html
Below is a selection of titles
regards
Michael Paine
Water on Mars: The View From Geochemical Analyses of Martian
Meteorites
>From Gullies to Glaciers: A Continuum of Evidence Supporting
a Recent
Climate Change on Mars
Impact Observations and Processes
Large Deep-Ocean Impacts, Sea-Floor Hiatuses, and Apparent Short
Term
Sea-Level Changes
Shock vaporization of carbonate and sulfate minerals
Remote Sensing in the Vicinity of the El'gygytgyn Impact Crater,
Siberia
Internal structure of the Chicxulub Impact crater imaged with
magnetotelluric exploration
Geophysical Signature of the Lake Bosumtwi Impact Crater, Ghana
The 2001 and 2002 Leonid Meteor Storms
First results from the 2001 Leonid storms: advances in models of
meteors
and meteoroid streams
Dust in the Earth's Mesosphere: Terra Incognita
A New Atmospheric Interaction Model for Leonids Entry
NEAR and Beyond (session title)
Deep Space One's Encounter with Comet Borrelly (session title)
Advances in Modeling Flow Processes:Volcanoes, Floods, Impacts,
and
Mass Movements
(session)
Ewing Structure: A Possible Abyssal Impact Crater (about the age
of the
late/middle Miocene boundary, a prominent mass extinction event)
Asteroids, Meteorites, and Comets (session)
Multiplicity in the Kuiper Belt: The First Discovery of a Binary
Trans-Neptunian Object
Three Dimensional Simulation of Wave Propagation Into the Comet
46P/Wirtanen Nucleus (ROSETTA Space Mission - CONSERT Experiment)
Temporal Change of the Fireball Energy along the Fall Path from
Shock
Wave Analysis
Small Comet Abundance and Solar System Location
Origin of Scour in Rampart Crater on Mars
===============
(7) NASA GODDARD JOINS TEAM TO EXPLORE THE SOLAR SYSTEM'S FINAL
FRONTIER
>From Andrew Yee <ayee@nova.astro.utoronto.ca>
William Steigerwald
NASA Goddard Space Flight Center, Greenbelt,
MD Dec. 7, 2001
Phone: 301/286-5017
wsteiger@pop100.gsfc.nasa.gov
RELEASE NO: 01-121
NASA GODDARD JOINS TEAM TO EXPLORE THE SOLAR SYSTEM'S FINAL
FRONTIER
At the edge of our solar system lies a frigid double planet that
has never
been visited by spacecraft -- Pluto. NASA's Goddard Space Flight
Center,
Greenbelt, Md., has joined a team led by the Southwest Research
Institute
(SwRI), San Antonio, Texas, to begin preliminary design
studies for what could be the first spacecraft to visit this
remote world --
the New Horizons mission.
Goddard will provide an infrared spectrometer, called the Linear
Etalon
Imaging Spectral Array (LEISA), to the camera system on board the
New
Horizons spacecraft. A spectrometer breaks light down into its
component
colors, much like a prism separates white light into a rainbow.
Each
compound emits a unique pattern of colors, like an optical
barcode. By
separating light from a celestial object into various distinct
colors, a
spectrometer reveals the optical barcode of any material present.
With this
information from LEISA, astronomers will determine what Pluto and
Charon,
Pluto's unusually large moon, are made of, at least on their
surfaces.
"We are thrilled to collaborate with the Goddard Space
Flight Center," said
Dr. Alan Stern of SwRI, Principal Investigator for the New
Horizons mission.
"Goddard has world-class people and world-class
technology."
"Pluto is nearly three billion miles from the Sun, more than
thirty times
farther away than Earth, so remote, very little is known about
it," said Dr.
Donald Jennings, a Co-Investigator for New Horizons at Goddard.
"Even with
the Hubble Space Telescope, Pluto's surface features remain a
tantalizing
blur. Sending a spacecraft for a close-up view is the only way to
learn more
about Pluto, whose moon, Charon, is so large that Pluto qualifies
as a
double planet."
Congress provided $30 million in fiscal 2002 to initiate the
spacecraft and
science instrument development and launch vehicle procurement for
a
Pluto-Kuiper Belt mission; however, no funding for subsequent
years is
included in the administration's budget plan.
If the design passes a NASA review and the mission is fully
funded by
Congress, New Horizons will be sent to explore Pluto, whose orbit
takes it
farther from the Sun than any planet in the solar system. Pluto
is the
largest member of the Kuiper Belt. Kuiper Belt Objects (KBOs) are
a class of
relatively small worlds at the fringe of our solar system,
possibly hundreds
of millions strong, composed of material believed to have been
left over
after the formation of the other planets.
The New Horizons mission, planned for launch in January 2006,
will explore a
number of KBOs after it flies past Pluto between 2016 and 2018.
The
mission's exact arrival time at Pluto depends on the rocket
selected to
launch the spacecraft. On the way to Pluto, the New Horizons
spacecraft will
pass close to Jupiter, gaining a boost from the giant planet's
gravity to
achieve the speed necessary to reach the outer solar system in a
reasonable
amount of time. This flight path will present the next
opportunity to
explore Jupiter's exotic moons, and the mission intends to take
full
advantage of it.
"Pluto's extreme distance makes it the only planet
unexplored by
spacecraft," said Dr. Dennis Reuter, sensor program manager
for LEISA. "It's
an extraordinary challenge to reach. To travel to Pluto in a
practical
amount of time and survive the trip, the spacecraft and its
instruments must
be built with unprecedented reliability, low weight, and low
power
consumption."
The camera team will provide a camera and instrument package
called the
Pluto Express Remote Sensing Investigation (PERSI) that weighs
less than 22
pounds and consumes less than seven watts of power. The package
is comprised
of three subsystems. First is a system of six cameras, to be
provided by
Ball Aerospace, Boulder, Colo., called the Multi-spectral Visible
Imaging
Camera (MVIC). MVIC will take detailed pictures of Pluto and
Charon. It is
called a multi-spectral
camera because it is capable of making images with various kinds
of light:
visible light, ultraviolet light, and infrared light. Ultraviolet
and
infrared light are not visible to the human eye.
Second is LEISA, the infrared spectrometer to be provided by
Goddard. The
third subsystem is an ultraviolet spectrometer, to be provided by
SwRI,
called Alice because it's such a nice name. Alice will analyze
ultraviolet
light to reveal the composition of Pluto's extremely tenuous
atmosphere.
Ball will be responsible for assembling the three PERSI
subsystems into a
complete package.
"Each instrument team is among the best in its field, so we
combined our
strengths for the New Horizons camera system, providing a package
smaller
and less costly than previously possible, which is ideally suited
to the
Pluto and Kuiper-belt science," said Jennings. "Goddard
has supplied
infrared spectrometers for many missions, including Voyager,
COBE, Cassini
and EO-1. SwRI has a strong background in space-borne ultraviolet
experiments, and is supplying Alice for the Rosetta mission. Ball
has a long
and highly successful record of building a variety of space
instruments."
The instrument package was developed, lab and flight tested over
a period of
eight years, beginning with NASA "Advanced Technology
Insertion" funds
specifically targeted at the advanced sensor and miniaturization
needs of a
Pluto mission.
In addition to SwRI, Ball, and Goddard, the New Horizons team
includes The
Johns Hopkins University Applied Physics Laboratory (APL) in
Laurel, Md.,
NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif., and a
variety of
other universities and research institutions. APL will manage the
mission
for NASA and design, build and operate the New Horizons
spacecraft. JPL will
provide navigation support, and tracking and communication
services through
NASA's Deep Space Network. SwRI will lead the science team and
guide
development of the spacecraft's scientific instruments, while
Ball Aerospace
and NASA Goddard help develop the payload.
==============
(8) 'RESTLESS EARTH' MAY GIVE ADVANCE NOTICE OF LARGE EARTHQUAKES
>From Andrew Yee <ayee@nova.astro.utoronto.ca>
John Bluck
NASA Ames Research Center, Moffett Field,
Calif. Dec. 7, 2001
650/604-5026 or 604-9000
jbluck@mail.arc.nasa.gov
AGU Moscone Center press room, rm. 111, San Francisco, Calif.
(Phone: 415/905-1007, general AGU information during meetings)
RELEASE: 01-100AR
'RESTLESS EARTH' MAY GIVE ADVANCE NOTICE OF LARGE EARTHQUAKES
Signals that come from deep within the Earth eventually may give
us a few
days' warning before some large earthquakes, according to a
scientist at
NASA's Ames Research Center.
The source of these signals lies deep in the Earth's crust, where
forces
squeeze rocks to the limit before they rupture catastrophically,
shaking the
ground with destructive force, according to Friedemann Freund, a
scientist
at NASA Ames, in California's Silicon Valley. He will present his
discoveries and theory on Wednesday, Dec. 12, at 1:30 p.m. PST in
the
seismology section of Hall D, Moscone Center, San Francisco,
during the 2001
American Geophysical Union (AGU) fall meeting.
"The challenge is to learn how to read and to decipher the
signals," Freund
said. "The best way is to try to better understand the
physics of the
processes that underlie these signals. A step forward was the
discovery of
dormant electric charges in rocks in the Earth's crust," he
said.
Earthquakes occur when tectonic plates, huge jigsaw-like sections
of the
Earth's outermost layers, rub against each other. Sometimes they
collide
head-on. In California, huge slabs of rock slide past each other,
causing
temblors along the San Andreas and other fault systems.
Freund has been investigating how rocks respond to stress.
"If the stress
level is high, electronic charges appear that momentarily turn
the
insulating rock into a semiconductor," he said.
Semiconductors are materials
that have a level of electrical conductivity between that of a
metal and an
insulator, and they are used to make transistors.
"These charges are not easy to pin down. They move with
impressive speed, as
fast as 300 meters (1,000 ft.) per second," he said. By
measuring the
semiconductor properties of the rocks, Freund was able to show
that the
charges are positive. "Normally, these charges are
dormant," he said. "But
when rocks are squeezed, the charges wake up and flow out of the
rock volume
in which they were generated."
When charges flow, they constitute an electric current. When
there is an
electric current, there also is a magnetic field. If current
varies with
time, electromagnetic waves will be emitted.
"The frequency of these electromagnetic waves will probably
be very low,
much lower than radio waves, but basically of the same
nature," said Freund.
"Scientists can pick them at the Earth's surface with
suitable antennae or
by measuring the magnetic-field pulses that go with them."
"What happens when the charges reach the Earth's surface?
They will change
'the ground,'" said Freund. "They should cause the
Earth's surface to become
positively charged over a region that may measure tens or even
hundreds of
kilometers. The Earth's ionosphere is bound to react," he
said.
The ionosphere lies above the atmosphere, starting at about 90 km
(56 mi.)
and extending to about 300 km (190 mi.) into space. "When
the surface of the
Earth becomes positively charged, the charged plasma in the
ionosphere must
respond," said Dimitar Ouzounov, a scientist from NASA
Goddard Space Flight
Center, Greenbelt, Md., who is working with Freund. The
ionospheric plasma
is very thin air that contains many free electrons and positive
ions. In the
lowest layers of the
ionosphere, which reflect radio waves, the plasma is positively
charged.
When the Earth's surface becomes positively charged, the plasma
is pushed
aside, and energetic electrons from the upper layers can
penetrate more
deeply into the lower part of the ionosphere. This in turn
affects the
transmission of radio waves, especially in the short wave region,
as was
noticed in the 1960s, in the days before the huge 1961 Chilean
earthquake
and the nearly equally large Good Friday earthquake in Alaska in
1964.
"These ionospheric changes can also be studied from
satellites. Russia,
France and Japan are close to launching satellites dedicated to
investigating these phenomena," Freund said.
"But what has been lacking in the past was a physical
explanation of how
electric charges can be created in the Earth's crust," said
Freund. "These
are charges that move around, emit all kinds of signals, and can
even reach
the Earth's surface. There they give rise locally to very high
electric
fields, and change 'the ground' charge."
"When the rocks in the Earth's crust crackle and buckle
under the onslaught
of tectonic forces, the charges that are dormant in them are set
free. They
give rise to a dazzling array of phenomena, long known to mankind
and even
part of folklore in earthquake-prone regions around the
globe," said Freund.
"These phenomena range from anomalous electric and magnetic
signals, to
'earthquake lights' that illuminate the mountain tops and strange
animal
behavior as well as ionospheric effects that impact how radio
waves travel
over long distances."
"It is both surprising and comforting that many seemingly
disjointed or even
inexplicable phenomena that point to impending earthquake
activity seem to
have just one cause -- the awaking and spreading of normally
dormant charges
in the rocks deep in the Earth," he said.
"It is much too early and, in fact, unwise to expect that
earthquakes would
soon become predictable beyond the statistical probability that
is currently
the state-of-the-art," Freund said. "But one day, we'll
learn to read the
signals that the restless Earth emits before the rocks rupture
with deadly
force."
===============
(9) SPACE MEMORIAL FOR 11 SEPTEMBER
>From the BBC Online News, 10 December 2001
http://news.bbc.co.uk/hi/english/sci/tech/newsid_1701000/1701274.stm
American and Russian crews on the International Space Station and
the
shuttle Endeavour have held a televised ceremony to commemorate
those who
died in the 11 September attacks in the US.
The commander of the outgoing space station crew said they had
seen the
smoke over New York and Washington on the day of the attacks as
they orbited
the earth.
Endeavour is carrying thousands of small flags intended for
relatives of
those who died in the attacks and also has on board a flag
retrieved from
the World Trade Center.
The Russian commander of the new crew said he was glad to see the
US and
Russia co-operating in the anti-terror coalition.
Yuri Onofrienko said the space station programme symbolised the
benefits of
international co-operation.
'Terrible' sight
Frank Culbertson, commander of the outgoing space station crew
which has
been on board since August, recalled what it was like when they
first heard
of the attacks.
The crew were able to see the effect of the attacks from space
"We were flying over North America at the time," he
said, "so we were able
to look out one of the windows and actually see New York City
under attack."
"That was quite a disturbing sight, as you can imagine... I
believe all
three of us were thinking how terrible this must be for the
people that were
at the point of attack and for their families," he added.
Endeavour Commander Dom Gorie also paid tribute to "the
armed forces around
the world, who are doing their best to stop this global threat of
terrorism".
Flying high
Mr Gorie said that the shuttle was carrying 6,000 flags which
will be
distributed later to the families of those killed on board the
hijacked
airliners.
Two were flown into the World Trade Center, one into the Pentagon
and one
crashed in Pennsylvania after a passenger revolt.
Also on board is a US flag that had been flying on top of the
World Trade
Center, which was later retrieved from the rubble of the
collapsed
buildings.
The ISS is held up as an example of international co-operation
"It has a few tears in it; you can still smell the
ashes," Mr Gorie said.
"It's just a tremendous symbol of our country. Just like our
country was a
little bit bruised and battered and torn, with a little repair,
it's going
to fly high and as beautiful as it ever could, and that's just
what our
country is doing," he added.
The shuttle is also carrying a flag found in the Pentagon after
the attack,
a flag from the state of Pennsylvania and another from the New
York Fire
Department, as well as a selection of shields from the New York
Police
Department.
New York's emergency services were amongst those who bore the
brunt of the
September attacks.
Endeavour is scheduled to return to Earth with the outgoing crew
on 16
December.
Copyright 2001, BBC
============================
* LETTERS TO THE MODERATOR *
============================
(10) MIOCENE OCEAN IMPACT?
>From Michael Paine <mpaine@tpgi.com.au>
Dear Benny
One of the AGU abstracts (http://agu.org/meetings/fm01glan.html)
I mentioned
in my earlier email was on the Ewing Structure. Dallas Abbott
estimates it
has a crater diameter between 55 and 150km - a significant impact
- and
"about the age of the late/middle Miocene boundary, a
prominent mass
extinction event". With my limited resources I cannot find a
reference to
such an extinction event but did find this interesting New
Zealand site
http://www.gns.cri.nz/earthhist/ancient_env/current/impact.html
"The middle part of the Miocene Epoch, a time period from 11
to 16
million years ago, was crucial in the development of the modern
global
climate regime. It was during this period that a huge ice-sheet
first
formed on eastern Antarctica, essentially shaping the earth's
climate as
we see it today."
I can speculate that a major ocean impact would have released
vast
quantities of seawater into the atmosphere and caused severe
global colling
for at least a year. Such a combination MIGHT have been enough to
start off
the ice sheet.
An interesting one to watch!
regards
Michael Paine
=============
(11) KING DAVID'S COMET & IMPACT
>From Göran Johansson <swe99acad@tjohoo.se>
Psalm 18 in the Bible has been discussed on several occasions on
CCNet. And
2 Samuel 22 has also been mentioned. According to the modern
comments, they
are believed to be related to each other. And the second item
should be very
late during the reign of King David, unless it is anachronistic.
"When David looked up and saw the angel of the Lord standing
between
earth and heaven, and in his hand a drawn sword stretched out
over
Jerusalem, he and the elders, clothed in sackcloth, fell
prostrate to
the ground." 1 Chronicles 21:16.
Chronologically it may be from the same time as 2 Samuel 22. This
item has
often been interpreted as a comet. Some of you are probably
familiar with
the comet catalogue Ho compiled (1962, Vistas in Astronomy, vol.
5, pages
127-225) "In spring, in the 19th year of (Chou) Chao-Wang a
(po) comet
appeared within the Thai-Wei (Enclosure)."
When did the comet appear? There are chronological problems but
hardly
anybody would protest against a date sometime during the 970s or
960s BCE.
The story in the Bible occurred during spring but I can't tell
the exact
week because I don't know when people would thresh wheat.
"The Legends of the Jews" is 7 volumes of non-Biblical
Jewish legends,
edited by L. Ginzberg, which has been reprinted several times. On
page 15 in
volume 5, it is mentioned that a meteorite fell down outside
Jerusalem on
that place where the temple was later built. Admittedly it is
improbable
that a meteorite would fall down on a specific place, so perhaps
the people
moved a meteorite to the place where they later built the temple.
G H I Johansson
=============
(12) THERA AND THEOGONY
>From Bruce Lerro <goethe48@pacbell.net>
Hi Benny:
Just wanted to alert you and other folks about a book called
"Natural
Knowledge in Preclassical Antiquity" by Mott Greene (Johns
Hopkins Press,
1992). The author has two very interesting chapters comparing the
Theogony
of Hesiod to the Thera eruption and another eruption in Sicily
around the
7th century BCE. The good news is Greene seems well versed in
geology and
his comparison of Hesiod's text to our current geological
knowledge seems
more specific than the usual comparisons.
Bruce Lerro
===========
(13) NEW WORKING PAPER ON DISASTER MANAGEMENT
>From John Twigg <j.twigg@UCL.AC.UK>
Some of you may be interested in a new working paper published
online by the
Benfield Greig Hazard Research Centre.
Author: Annelies Heijmans
Title: 'Vulnerability': a matter of perception.
The paper looks at different ways of viewing vulnerability,
focusing on how
poor people think of it.
You can download it from the Benfield Greig Hazard Research
Centre website
(http://www.bghrc.com) - go to
the Disaster Management pages for this and
the others in the series of working papers.
=============
(14) AND FINALLY: FIRE SCARE GONE MAD - SCIENTIST WANTS TO BAN
CHRISTMAS
TREES
>From Ananova, 8 December 2001
http://www.ananova.com/news/story/sm_468606.html?menu=news.scienceanddiscovery
Scientist wants to ban Christmas trees
A Dutch scientist wants to ban all Christmas trees from houses
and churches.
Freed Paap says Christmas trees are a fire safety hazard and
should never be
put up indoors. He is a research scientist and safety expert.
He says its impossible to make a non-flammable Christmas tree so
they should
all be banned from buildings.
Mr Paap, who works for the Netherlands Organisation for Applied
Scientific
Research (TNO) said all Christmas trees in bars and restaurant,
schools,
churches and public buildings should be forbidden for safety
reasons.
He said materials in buildings should always be made
non-flammable.
But Mr Paap says no Christmas trees, real or artificial, are
non-flammable
so they should be banned from in-doors.
"It's impossible to make them really not inflammable,"
Mr Paap said.
"The results for artificial trees are much better but not
really sufficient.
Therefore all christmas trees should be forbidden," he told
Utrechts
Nieuwsblad.
Holland suffered a horrific Christmas tree related inferno
accident last
Christmas-time.
On New Years Day 2001, 14 teenagers were killed and 184 injured
in a fire in
a pub in Volemdam which was caused by burning Christmas tree
twigs.
Copyright 2001, Ananova
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