PLEASE NOTE:
*
CCNet 23/2003 - 28 February 2003
---------------------------------
"When Comet C/1976 D1 Bradfield passed uncomfortably close
to
Earth's orbit on its sweep through the inner solar system, it was
a
faint +8 magnitude binocular object in the Southern hemisphere.
It's
passing was poorly communicated by observers who lacked today's
connectivity. The best determination astronomers can make of the
comet orbit
places a return visit about 1,000 years into the future. Before
we
all heave a sigh of relief, thousands of such comets remain
undetected.
A similarly sized comet in such a fast moving orbit in another
solar
system may long ago have wiped out a civilization before it could
be
detected in our SETI searches."
--Peter Jenniskens, Space.com, 27 February 2003
(1) CLOSING IN ON NEAR EARTH OBJECTS
Space.com, 27 February 2003
(2) A RARE METEOR SHOWER
NASA News, 28 February 2003
(3) METEOR-LIKE OBJECT SEEN IN SHARJAH (UNITED ARAB EMIRATES)
Khaleeji Times, From 27 February 2003
(4) THE PURSUIT OF 2003 CR20
Asteroid/Comet Connection, 27 February 2003
(5) BIOLOGICAL PROCESSES ASSOCIATED WITH IMPACT
Charles Cockell <csco@bas.ac.uk>
(6) ASTEROIDS & SECRETS
MSNBC, 26 February 2003
(7) CONTROVERSIAL PROPOSAL WOULD BOOST SOLAR SYSTEM'S PLANETARY
TALLY TO 12
Space.com, 27 February 2003
(8) RE: THE GREAT IMPACT DEBATE
Mark Kidger <mrk@ll.iac.es>
(9) AND FINALLY: AN URBAN ASTEROID LEGEND
The Chicago Sun Times, 24 February 2003
=============
(1) CLOSING IN ON NEAR EARTH OBJECTS
>From Space.com, 27 February 2003
http://www.space.com/searchforlife/seti_neo_030227.html
By Peter Jenniskens
Principal Investigator, SETI Institute
While many astrobiologists follow the water, some are following
the
dirt. SETI Institute astronomer Peter Jenniskens is hot on the
trail of an
elusive comet whose last visit was in 1976, and whose lingering
debris may
help scientists warn us about the imminent return of a mysterious
class of
Near Earth Objects (NEOs).
--
We believe that prediction models tested on the Leonid showers
can also be
used to predict when these dust trails are steered in the Earth's
path by
the gravitational influence of planets, and we are about to
travel to South
Africa to observe a new meteor shower thus predicted.
When Comet C/1976 D1 Bradfield passed uncomfortably close to
Earth's orbit
on its sweep through the inner solar system, it was a faint +8
magnitude
binocular object in the Southern hemisphere. It's passing was
poorly
communicated by observers who lacked today's connectivity. The
best
determination astronomers can make of the comet orbit places a
return visit
about 1,000 years into the future.
Before we all heave a sigh of relief, thousands of such comets
remain
undetected. A similarly sized comet in such a fast moving orbit
in another
solar system may long ago have wiped out a civilization before it
could be
detected in our SETI searches.
The key to finding the approaching comets is to recognize the new
meteor
shower when Earth hits its dust trail.
In a paper soon to be published in the journal Icarus, Finnish
colleague
Esko Lyytinen and I predict a number of such showers, first on
the list is
the trail of C/1976 D1.
Joining members of the Astronomical Society of South Africa -
Meteor section
just outside of Cape Town in South Africa, we hope to witness the
meteor
outburst, which peaks at 21:54 GMT (give or take 20 minutes) on
March 1 and
will last for approximately half an hour (14 minutes, full-width
at
half-maximum). The shower's radiant will be in the southern
constellation
Tucana, the Toucan, and will become known as the "Beta
Tucanids."
The dust trails stretch far in front of and behind the comet, but
that only
when the planets cooperate can we observe a meteor shower.
Jupiter and the
other large outer planets in our solar system tug upon the path
of comet
dust particles. The tugging perturbs the orbits of the dust
trails such that
they are moved into Earth's path about once or twice every sixty
years,
through the combined effects of Jupiter and Saturn planets with
12 and
30-year rotation periods.
A successful observation will help read other such showers for
useful
information regarding their parent comet. These encounters offer
a chance to
study the comet's debris and infer properties such as comet size,
surface
composition, and orbit. Repeated observations can in principal
reveal
whether a long period comet is approaching us, or returning back
to the dark
frontier of the solar system far beyond the outer planets.
The viewing location is not ideal-unfortunately, the best seats
in the house
are found in hard to get to locations in Antarctica. Are we
disappointed
that we may never see this elusive comet again? Not at all.
What's left
behind after the comet has departed can provide as important
information and
we're learning to read the playbill.
Copyright 2003, Space.com
===========
(2) A RARE METEOR SHOWER
http://science.nasa.gov/headlines/y2003/28feb_tucanids.htm?list20392
Earth is approaching a cometary debris stream that might trigger
an unusual
Antarctic meteor shower this weekend.
February 28, 2003: "We all felt like we needed to put on
'hard hats'! The
sky was absolutely full of meteors," recalls astronomer Jim
Young of JPL's
Table Mountain Observatory. Earth had just plunged into a debris
stream
trailing comet Tempel-Tuttle; the resulting meteor storm, the
1966 Leonids,
was literally dazzling.
This weekend it could happen again.
On March 1, 2003, around 2154 universal time (UT), our planet
will encounter
a stream of dusty comet debris "only 12,000 km from Earth.
That's as close
as the Leonid debris stream was in 1966," says Bill Cooke of
the NASA
Marshall Space Flight Center's Space Environments Team.
The source of the dust this time is Comet Bradfield (C/1976
D1)--a dim comet
discovered in 1976 by Bill Bradfield of Australia. It swings
through the
inner solar system approximately every 1000 years.
"We've never observed a meteor outburst from Comet Bradfield
before," says
Cooke. That's no surprise: The comet's orbit is tilted so the
shower is
visible only from the far-reaches of our planet's southern
hemisphere. The
best viewing spots are near the coast of Antarctica ... "and
onboard the
International Space Station," adds Cooke.
Researchers are interested in this remote shower because of its
source: a
long-period comet.
Most meteor showers, like the Leonids, are caused by short-period
comets
that circle the Sun every few years or decades. These frequent
visitors are
easy to find and are routinely tracked by astronomers. Long
period comets,
on the other hand, spend most of their time in the dark recesses
of space
beyond Pluto; the vast majority remain undiscovered. With little
warning one
could swoop in from the outer solar system and pass uncomfortably
close to
our planet.
Peter Jenniskens of the NASA Ames Research Center and the SETI
Institute
thinks meteor showers might provide a distant early warning
system for such
objects. He and colleague Esko Lyytinen recently examined the
orbits of dust
from all known long-period comets and identified five potential
new showers
during the next 50 years--including this weekend's. Although
Comet Bradfield
doesn't pose a threat to Earth, says Jenniskens, it might show us
what a
"long-period meteor shower" looks like.
Jenniskens is traveling to Cape Town, South Africa. "I'll
try to observe
this outburst with the help of members of the Astronomical
Society of South
Africa, led by Tim Cooper," he says. Even at the southern
tip of Africa,
though, meteors will be difficult to see. The shower's radiant is
in the
constellation Tucana, the Toucan, which passes overhead at -64o S
latitude.
Tucana will be just 14o above the horizon of Cape Town during the
expected
peak, its low altitude greatly reducing the number of visible
meteors. "I'll
be happy to see any at all," says Jenniskens.
Astronauts have a better view. "The International Space
Station will be over
the southern hemisphere in an excellent position to view any
meteors from
this event," says Cooke. Looking out the station's windows,
members of the
crew might be able to spot meteoroids disintegrating in the
atmosphere
below. "Even if it turns into a full-fledged meteor storm,
which I doubt,
there's no danger to the heavily-armored station," he says.
The crew can
relax and enjoy the show. (Recommended reading: Science@NASA's "Space
Station Meteor Shower.")
This isn't the first dust trail from a long-period comet
Jenniskens has
studied. In 1995, members of the Dutch Meteor Society assisted
him in
triangulating meteors from a spectacular burst of
alpha-Monocerotids over
Spain that year. They demonstrated that the dust was in a long
period orbit
(much longer than 150 years). "That shower proved
long-period comets have
dust trails," he says. "And it showed peculiar aspects
such as sodium-poor
meteoroids with unusually high density."
Are those the telltale signs of a long-period comet? This
weekend's outburst
could provide valuable data. Or not. It may be that no one has
ever seen
meteors from Comet Bradfield because there are none to see. Yet
Jenniskens
doesn't need a dazzling storm like the 1966 Leonids to learn what
he wants
to know. Even a few shooting stars on March 1st would be a big
event.
===========
(3) METEOR-LIKE OBJECT SEEN IN SHARJAH (UNITED ARAB EMIRATES)
Khaleeji Times, From 27 February 2003
http://66.234.3.46/DisplayArticle.asp?xfile=data/theuae/2003/February/theuae_February370.xml§ion=theuae
By Tarek Fleihan, Meraj Rizvi, Zaigham Ali and Hani Bathish
SHARJAH - In what could be described as a rare celestial
spectacle, a
meteor-like fiery object was seen shooting across the skies in
Sharjah and
was incidentally captured on tape for over four minutes by Talal
Hajjar, a
student of the American University of Sharjah (AUS), at around
6:30pm
yesterday.
'I was driving by the men's dormitory when I pulled over after
noticing this
huge ball of fire streaking across the sky along a sharp axis
towards the
East at great speed and my first impression was that may be it
was a common
occurrence,' said Mr Talal, recounting his first reaction. 'But
something
told me that it was extraordinary, and I ran back to the car and
pulled out
my camera, which I was carrying because of the Mass Communication
Media
filming project and the constant pressure from my teacher
Professor
Beagalow,' said Mr Talal excitedly.
The meteorological offices in Dubai and Sharjah said that the
available
satellite pictures suggest no unusual activity in the skies.
'This sort of
thing is too small to register on a satellite picture, more so
because at
one particular time, we cover a limited area,' said one
weatherman.
According to a geological expert in the UAE, the falling object,
if it did
fall to the ground, would have created enough vibrations to be
picked up by
a seismograph, the instrument used to detect earthquakes. He said
that the
falling object either did not reach the ground and just burnt up
in the sky,
or if it did reach the ground it fell in the sea.
>From the fiery orange tail and the speed of its descent,
estimated by an
amateur astronomer to be over Mach 20, among the explanations
produced is
that it is either space debris or a large meteorite.
===========
(4) THE PURSUIT OF 2003 CR20
>From Asteroid/Comet Connection, 27 February 2003
http://www.hohmanntransfer.com/sas/cr20/index.html
By Bill Allen, A/CC Editor & Links Librarian
Following the case of potentially hazardous object 2003 CR20 is a
special
opportunity to watch the near-Earth object (NEO) impact risk
monitoring
community at work. Parts or all of this community are sometimes
called
"Spaceguard," borrowed from Arthur C. Clarke's
Rendezvous with Rama s-f
novel. However, the entire effort is actually a loose and
unofficial but
very cooperative ad hoc assemblage of groups and individuals. At
the top is
the International Astronomical Union (IAU) Minor Planet Center
(MPC), which
receives, processes, and reports out astronomical photometric
observations,
which are then used by the NEO Dynamic Site (NEODyS, at the
University of
Pisa in Italy) and the newer NASA JPL NEO Program (at Caltech in
Pasadena,
California) to prepare their independent risk analyses. The
observations
come from sources ranging from the NASA-funded and Air
Force-assisted LINEAR
and NEAT NEO surveys, to institutionally-backed NEO surveys such
as LONEOS
and Spacewatch, through many other professional and university
observatories
around the world, and a network of "amateurs" who at
their own expense
provide most of the very critical "follow-up"
observational effort. (It
wouldn't do much good for the big programs to discover NEOs if
someone
didn't track the objects further to keep from losing them.)
See below for a table showing the progression of risk analysis
for 2003
CR20. And read on for a taste of the effort's daily progress.
----------------------------------------------------------------------------
----
Both NEODyS and JPL added 2003 CR20 to their Risk pages on 14
Feb., with it
debuting in JPL's top slot with a cumulative Palermo Scale rating
of -1.86,
but with a Torino Scale rating of 0 (see hazard scales). This
object was
discovered by JPL's NEAT program with its Hawaiian telescope on
11 Feb. 2003
and was announced early on the 14th. It is now estimated at about
560
meters/yards wide.
In posting 2002 CR20 to its observing campaigns page on 14 Feb.,
the
European Spaceguard Central Node noted that CR20 is "going
to be visible for
at least two months, leaving a lot of room for orbital
improvement" to be
accomplished.
Early on most days, the MPC issues a Daily Orbit Update (DOU)
Minor Planet
Electronic Circular (MPEC) with formatted revised orbital
elements for
asteroids generally, and new observations for near-Earth
asteroids. The DOU
MPEC is the primary means for conveying new positional data to
the risk
monitors, and most changes in NEODyS and JPL risk assessments
follow receipt
of this data.
The first DOU MPEC following 2003 CR20's announcement, that of
the 15th, had
no new observations. And no DOU MPECs were issued during 16-18
Feb., there
being a lull in observations due to the full Moon, a period used
by the MPC
and risk monitors for database and systems maintenance.
The next DOU came on the 19th and reported four positions taken
at La Silla
on 15 Feb. for 2003 CR20. That was sufficient to remove 59% of
JPL's initial
impact solutions, also called "virtual impactors"
(VIs), but also slightly
raised the risk monitors' maximum and median (cumulative or
averaged)
Palermo Scale ratings.
----------------------------------------------------------------------------
----
The DOU for the 20th reported 2003 CR20 observations of the 18th
from La
Palma and on the 19th from Klet Observatory. The net result shown
in the
revised NEODyS hazard assessment was to remove six of 25 impact
solutions
while slightly bringing up its average Palermo Scale rating for
the
remaining solutions. With this, NEODyS raised the Torino Scale
rating from 0
to 1 ("merits special monitoring") for a VI for 17
March 2046. JPL did the
same when it brought out its new assessment, while showing very
slightly
reduced Palermo Scale ratings overall, and while removing 105 of
139 VIs.
This feat of JPL chopping 75% of its remaining 139 VIs at one
swoop from
just two days' further observation demonstrates how the matter of
2003 CR20
was still very early in its follow-up effort, just over a week
after its
discovery.
The DOU for 21 Feb. reported observations of the 20th from Powell
and
Sormano observatories. An updated NEODyS assessment had one less
impact
solution and very slightly lowered the average Palermo Scale
rating,
although a revision later in the day pretty much reversed that.
JPL took
until after lunch to update its assessment, dropping nine more
impact
solutions while very slightly raising its cumulative and maximum
PS ratings.
>From 21 Feb. comes this image of 2003 CR20 by Rafael Ferrando
at Pla
D'Arguines, forwarded by Pepe Manteca, who has posted an
animation.
----------------------------------------------------------------------------
----
On 22 Feb., the DOU reported 2003 CR20 observations of the 21st
from
Camarillo, Klet, and Pla D'Arguines observatories. With these,
NEODyS shed
another seven impact solutions, but the average and specific
Palermo Scale
ratings for the dozen remaining were up from the day before. The
JPL NEO
Program's new CR20 assessment removed three more impactors while
raising
cumulative and specific PS ratings. And both monitors this day
raised the
Torino Scale rating to 1 for a pair of impact solutions for 16
March 2061.
With less than eleven days of tracking, the 2003 CR20 observing
effort was
still producing only preliminary results. What you see reported
here is a
routine night-and-day progression of observation and analysis.
Out of many
potentially hazardous objects (PHOs) newly discovered every year,
several
such as 2003 CR20 rise in the evolving analyses to Torino Scale 1
before
being determined to pose no risk at all. The Torino Scale is for
public
consumption, while the Palermo Scale is a more complex scientific
tool. For
readers new to how impact risk monitoring works, and how
astronomers around
the world track concerns until the risks are disproven, please
read
"Understanding Risk Pages" by Jon Giorgini of JPL
(http://www.hohmanntransfer.com/by/giorgjon.htm).
----------------------------------------------------------------------------
----
The DOUs for 23 to 25 Feb. carried 2003 CR20 observations from La
Palma, and
from Jornada, Klet, and Sormano observatories, especially Klet.
This helped
shed more impact solutions while generally but only slightly
raising the
Palermo Scale ratings. On 26 Feb., new observations from Klet
were reported
in the day's DOU, and the trend in risk analysis seemed to
continue, except
that JPL's cumulative PS rating for CR20 dropped for the first
time, and the
NEODyS average PS also fell, both slight moves.
At this early point, with little more than 14 days of
observation, both risk
monitors show 13 impact possibilities spanning the years 2031 to
2073 that
still need to be eliminated. They aren't quite the same 13 impact
solutions
- JPL has one VI in 2031 and three in 2034, while NEODyS has two
VIs in 2031
and one in 2034, but overall the analysis is converging.
Something to understand about impact risk monitoring is that a
"virtual
impactor," or "impact solution," is not a
single-line path (and a
single-point impact) but rather a very large set of solutions for
the
Earth's immediate vicinity. The risk monitors work to eliminate a
general
possibility rather than to determine a specific certainty. Using
a sports
analogy, it's like trying to decide whether a ball can even get
into the
ballpark rather than will it score a goal or home run. In a
description for
general readers, JPL describes an asteroid's path as having a
region of
uncertain position that is a "three-dimensional tube
stretched along its
orbit." If that tube doesn't come to within an Earth radius
of Earth's
orbital path, a collision can't happen.
----------------------------------------------------------------------------
----
The DOU MPEC time-stamped 0707 UT on 27 Feb. carried no new
observations of
2003 CR20, but it did report new orbital elements, which can be a
sign that
new observations are in but aren't being passed through yet. More
than 12
hours later, sometime between 1950 and 2205 UT, both NEODyS and
JPL updated
their CR20 assessments. A check of the NEODyS 2003 CR20 optical
observations
page showed six positions taken by Klet Observatory during
2043-2050 UT on
the 26th, and JPL's assessment reported an equal number of
observations.
With this, both NEODyS and JPL dropped one impact solution, and
backed off
on both their maximum and their cumulative (JPL) and average
(NEODyS) PS
ratings. While the maximum Torino Scale rating remained at 1, it
is starting
to look like maybe the corner has been turned in the risk
analysis.
Watch A/CC News for the latest information on 2002 CR20.
----------------------------------------------------------------------------
----
2003 CR20 risk assessment progression
A Palermo Scale (PS) rating of 0.0 is equivalent to the random
"background
risk" of being hit by an asteroid without warning. Such
ratings have only
gone positive to publicly exceed 0.0 in two instances - the very
brief case
of 2002 NT7 last Summer, and 29075 1950 DA has a positive VI in
the year
2880. A rating rising above -2.00 will attract special interest
from those
close to impact monitoring. A continuing rise may cause the
Torino Scale
rating to be raised from 0 ("no likely consequences")
to 1 ("merits special
monitoring"), such as has happened with 2003 CR20. A PS
rating becoming more
negative is what we want to see, showing an improvement in risk
outlook.
VI count
years PSmax PSmed* T IAU MPC MPEC notes
14 Feb. -------------- ----- -----
S
----------------------------------
NEODyS 24 2006-2079 -2.57
-5.37 0 discovery MPEC has 11
observations
JPL 234 2006-2102
-2.37 -1.86 0 from 4 observatories
11-14 Feb.
15-18 Feb.-------------- ----- ----- -
----------------------------------
The 15
Feb. DOU had no CR20 observations. No DOU MPECs 16-18 Feb.
19 Feb. -------------- ----- -----
-
----------------------------------
NEODyS 25 2028-2077 -2.26
-4.91 0 DOU had 1 set of 4 positions from
JPL 139 2006-2099
-2.13 -1.69 0 1 observatory 15 Feb.
20 Feb. -------------- ----- -----
-
----------------------------------
NEODyS 19 2028-2073 -2.08
-4.37 1* DOU had 8 positions (2 sets) from
JPL 34 2026-2083
-2.22 -1.73 1* 2 observatories 18-19 Feb.
21 Feb. -------------- ----- -----
-
----------------------------------
NEODyS* 19 2028-2065 -2.09
-4.27 1 DOU had 6 positions (2 sets) from
JPL 25 2026-2099
-2.18 -1.70 1 2 observatories 20
Feb.
22 Feb. -------------- ----- -----
-
----------------------------------
NEODyS 12 2031-2061 -1.58
-3.13 1* DOU had 18 positions (a set of 2
&
JPL* 22 2026-2073
-1.62 -1.32 1* 2 sets of 8) from 3 obs.
21
Feb.
23 Feb. -------------- ----- -----
-
----------------------------------
NEODyS 15 2031-2061 -1.36
-3.50 1 DOU had 14 positions as 2 sets
JPL 19 2028-2073
-1.42 -1.17 1 from 2 observatories
22 Feb.
24 Feb. -------------- ----- -----
-
----------------------------------
NEODyS 12 2031-2073 -1.39
-3.37 1 DOU had 12 positions as 2 sets
JPL 15 2031-2073
-1.45 -1.14 1 from 2 observatories
23 Feb.
25 Feb. -------------- ----- -----
-
----------------------------------
NEODyS 13 2031-2073 -1.16
-3.26 1 DOU had 6 positions as 2 sets
from
JPL 14 2031-2073
-1.22 -0.98 1 2 observatories 24
Feb.
26 Feb. -------------- ----- -----
-
----------------------------------
NEODyS 13 2031-2073 -1.09
-3.42 1 DOU had 1 set of 6 positions from
JPL 13 2031-2073
-1.15 -1.04 1 1 observatory 25 Feb.
27 Feb. -------------- ----- -----
-
----------------------------------
NEODyS 12 2031-2073 -1.41
-3.79 1 Nothing in today's DOU, but 6 new
JPL 12 2031-2073
-1.46 -1.42 1 positions from 1 obs.
26 Feb.
__________
Footnotes:
*The PS "median" is given here as JPL's stated
"Cumulative Palermo Scale"
rating and as the average calculated from NEODyS impact solution
PS ratings.
Clearly these are different kinds of numbers, but they may trend
similarly.
*The Torino Scale rating of 1 first set on 20 Feb. is for a 17
March 2046 VI.
*The NEODyS 21 Feb. assessment shown is the second of two noted
that day.
*Starting with the 22 Feb. JPL assessment, all VIs are within the
NEODyS 2080 time horizon
*As of 22 Feb., a pair of VIs for 16 March 2061 have a Torino
Scale 1 rating.
---------
Note to journalists: This page (and most other reporting on the
A/CC site
unless otherwise credited) is from a journalist who follows this
field
closely but who is not an expert. Please see a list of contacts
for
qualified experts available to the news media for advice and
quotation.
Consult them before publishing articles about impact risk
possibilities.
------
© Copyright 2003 Columbine, Inc. - All Rights Reserved
===========
(5) BIOLOGICAL PROCESSES ASSOCIATED WITH IMPACT
>From Charles Cockell <csco@bas.ac.uk>
March 30th - April 1st, 2003, King's College, Cambridge
The deadline for the 10th ESF IMPACT conference is this Friday.
Information
for registration can be found at: http://pssri.open.ac.uk/ESF/
The conference will cover :
- Biological and ecological consequences of asteroid and comet
impacts
- The chronological sequence of biological change at the site of
craters after impact
- Ecology in water-filled impact craters
- Ecology in land-based impact craters
- Post-impact succession and recovery - comparison with volcanism
and other destructive agents
- Impact craters on Mars and other planetary bodies - biological
possibilities
__________________________
Dr. Charles Cockell,
British Antarctic Survey,
High Cross,
Madingley Road,
Cambridge.
CB3 0ET. UK
Tel : + 44 1223 221560
e-mail : csco@bas.ac.uk
==========
(6) ASTEROIDS & SECRETS
>From MSNBC, 26 February 2003
http://www.msnbc.com/news/876643.asp
If an unavoidable catastrophe like a killer asteroid were coming
your way,
would you want the public to be told about it?
* 1645 responses
Yes 75%
No 17%
Not sure 8%
Survey results tallied every 60 seconds. Live Votes reflect
respondents'
views and are not scientifically valid surveys.
============
(7) CONTROVERSIAL PROPOSAL WOULD BOOST SOLAR SYSTEM'S PLANETARY
TALLY TO 12
>From Space.com, 27 February 2003
http://www.space.com/scienceastronomy/planet_denitions_030227.html
By Robert Roy Britt
Senior Science Writer
Controversial Proposal Would Boost Solar System's Planet Tally to
12
In the same week that the planetary community learned a mission
to Pluto has
been approved, a hot debate has re-ignited over whether the small
world
deserves planetary status at all.
This time the argument is fueled by a newly proposed definition
for planets
that would instantly boost the solar system's tally to 12 or more
by
including one large, round asteroid and at least two faraway and
icy
brethren of Pluto.
The intellectual argument is civil yet laced with terms like
"arrogant" and
"embarrassment," pitting researchers within the same
institution against
each other.
The core of the problem is this: The International Astronomical
Union (IAU),
charged with categorizing objects in space, can define everything
from an
asteroid to a star but has no definition for a planet. Officials
never
needed one until new discoveries in recent years highlighted the
inadequacy
and a stark debate began.
An IAU statement admits to having "never officially defined
what constitutes
a planet." Furthermore, the IAU used "historical
practice in accepting the
eight planets that were known when the IAU was created and
accepting Pluto
as the ninth when it was discovered (in 1930) not long after the
formation
of the IAU."
FULL ARTICLE at
http://www.space.com/scienceastronomy/planet_denitions_030227.html
============================
* LETTERS TO THE MODERATOR *
============================
(8) RE: THE GREAT IMPACT DEBATE
>From Mark Kidger <mrk@ll.iac.es>
Dear Benny:
My apologies for a somewhat delayed response to the Great Impact
Debate.
On reading what was said, one thing struck me that I have no
doubt will have
also struck other readers and that is that some of the numbers
presented
could, if read uncharitably by the uninitiated, make people
wonder why we
are so worried about the asteroid threat and suggest that we stop
wasting
tax-payers' money.
One of the numbers quoted is that 80% of the impact threat is
from "large"
asteroids, that are more than 1km in diameter. However, we read
that more
than 50% of such possible impactors have been detected and that
90% will
have been located within 5 years. Despite a number of scares and
one
asteroid (1950 DA) that is out there and that may be a threat to
my many
times great grandchildren, so far Armageddon does not seem to be
just around the corner.
We also read that the so-called Tunguska events that are so
frightening (and
a Tunguska-type event in Arthur C. Clarke's "Rendezvous with
Rama" is the
spur for the creation of the fictional Spaceguard and was the
spur to much of the current
interest in the impact threat) that cause a major disaster will
happen only rarely: once
every 8000 years for an event that kills 1000 people, once every
40 000
years. These are frequencies so low that few people would take
them too
seriously (who really worries even about the far greater danger
of death
from an accident every time you get in your car?).
So, the real question is, and this is one that a social
anthropologist would
have to address is: if by 2008 there is no change and the numbers
continue
to be not so frightening to the majority of the population, how
long before
public opinion turns on the astronomers for making a fuss about
nothing and
wasting the money that they have paid in taxes?
Perhaps it is just as important to hammer home the less
spectacular, but
also important message that NEO search programmes are like
insurance on your
house. Nobody takes out insurance because the think that their
house WILL
burn down, but you sure as hell want to have it just in case that
"one in a
million" chance does come up. In the same way, we don't look
for NEOs
because one will hit the Earth next month, or next year, or next
century,
but we do it just in case the IS one out there with our number on
it. It's
our insurance policy on the Earth. After all, we know that sooner
or later
there will be an asteroid that hits us.
In other words, we need to balance carefully the messages that we
give the
public and politicians. Not too alarmist, because if it is the
chickens will
come home to roost when no real immediate threat is located, but
also not
too relaxed about it because as the danger of an immediate threat
receeds
suddenly these NEO programmes that are doing such an important
job may find
that they are not so attractive for funding and we may end up
missing
something important.
Episodes like 1997 XF11 are important for public awareness in the
sense that
they are objects that could have been a real threat (let's not
forget that
1997 XF11 *does* cross the Earth's orbit and it is only a matter
of luck
that the Earth will be somewhere else when that happens) but are
now
eliminated from the equation. In this sense they are not
"scares", but real
threats that do have to be eliminated. Most NEOs are,
fortunately,
inoffensive. Striking off the objects on the PHA list and being
able to say
one by one that we have them under control is an important job.
As of today,
quite apart from the missing large NEOs, there are 44 on the JPL
risk list,
of which two are "green" events (Torino 1) and one,
fortunately very small,
low velocity object (2000 SG344) that still has as large as a 1
in 500
chance of hitting the Earth.
Even if we are pretty sure that 2003 CR20, 1997 XR2, 2000 SB45
and 2000
SG344 will not hit the Earth, we need to scratch them off our
chore charts
and just make sure that the public knows that a few more objects
that just
could be a threat if we are unlucky, have been scratched from the
list and
that, as a result, our children and grandchildren and our planet
can sleep
just a little easier.
If you take the current data on the JPL Sentry page, the current
cumulative
impact risk from the 44 asteroids that have at least one direct
or virtual
impactor of probability greater than 1 in 10**10 is 0.00336, or a
surprisingly high 1 in 300 in the next century approximately from
February
26th 2003.
Of this, 50% of the total risk comes from 2000 SG344, which is
40-m in
diameter and would impact at very low velocity and almost all the
rest comes
from the objects 2000 LG6, 2000 SB45 and 2001 GP2 which are 10,
50 and 10-m
in diameter respectively and too small to cause real damage
unless they were
to impact in a densely populated area.
If we just limit ourselves to objects of 100-m in diameter or
larger, in
other words, objects large enough to do real damage if they were
to hit, the
cumulative probability is 0.000191 (1 in 5000) of an impact of
one of the 16
objects on the list. The second highest probability object on
this list is
2003 CR20, which is a 560-m diameter high-velocity impactor,
although its
risk is spread over 13 potential impacts, all of which are of
very low
probability individually.
To many people, a 1 in 5000 chance of a major impact in the next
century
would, if not alarming, be sufficient reason to keep an eye on
things,
wouldn't it?
Of course, within a few days or weeks 2003 CR20 will disappear
off the
threat list as astronomers do their job and tie down its orbit,
but it will
be replaced by some other new asteroid that poses a similar
potential
threat. Perhaps I've just picked a day to look at the numbers
when the
cumulative risk of an impact in the next century is particularly
high, but
the numbers have surprised me.
In other words, how you look at the numbers and the spin that you
put on
them is very important in the perceived risks.
Mark Kidger
===========
(9) AND FINALLY: AN URBAN ASTEROID LEGEND
>From The Chicago Sun Times, 24 February 2003
http://www.suntimes.com/output/quicktakes/cst-nws-qt24.html
Real gravity of the situation
News Item: "Sir Isaac Newton predicted that the world will
come to an end 57
years from now, a TV network said, based on a document from a
Jerusalem
archive."
News Item: "Earlier concerns that asteroid 2002 NT7 will
plough into the
Earth on Feb. 1, 2019, have faded away. Updated measurements of
the
1.2-mile-wide asteroid's orbit make it clear that we don't have
to worry
about being hit, although there's some concern about an impact in
2060."
Hmm.
MODERATOR'S NOTE: There is nothing to "hmm" about since
2002 NT7 is no
concern whatsoever!
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*
OTT: "THE TIME IS NOW: SOME ARGUE WE SHOULD WORRY ABOUT
INCOMING ASTEROIDS"
>From ABC NEWS, 27 February 2003
http://abcnews.go.com/sections/scitech/DyeHard/dyehard.html
By Lee Dye
Special to ABCNEWS.com
Feb. 27 - Long ago David Morrison grew tired of the snickers he
has heard
for these many years. Despite the fact that he is a senior
scientist with
the NASA, some people regard him as a bit of a nut.
He's a prophet of doom in a three-piece suit.
Morrison has been shouting into the wind for a couple of decades
now about a
very real threat that many prefer to dismiss. He believes an
asteroid or a
comet may be headed our way and could smash into the Earth with
catastrophic
consequences, maybe even wiping out all life.
Yup, you've heard that so many times now that you want to
chuckle. It's Star
Wars stuff. And besides, there's probably little we can do about
it anyway,
so why waste time worrying?
'Lesser' Asteroids Also Pose Threats
But in the years since he first began to boldly proclaim that we
need to
take this threat seriously, Morrison has picked up support, and
not just
from astronomers who are cataloguing celestial bodies that we
need to
monitor closely. A small number of experts in various fields are
joining the
struggle, convinced that we shouldn't give up the battle before
the fight is
joined.
One of them is Lee Clarke, associate professor of sociology at
Rutgers
University and a specialist in disaster preparations. Clarke
makes a point
that is too often ignored.
We are focusing too much, Clarke maintains, on the "doomsday
scenario." It
would only take one of the approximately 700,000 mega-asteroids
that are
whipping around our solar system to wipe out all life on Earth.
If one of
them hits us, we're toast, and that is so unthinkable that it has
turned
many off to Morrison's lament.
Clarke calls that a "low-probability, high-consequence
event," and it may
not happen for thousands, or millions, of years. If at all.
What is far more likely, Clarke and others maintain, is a
collision with a
lesser asteroid or a comet that may not be a "planet
killer," as he puts it,
but quite capable of creating catastrophic results.
"That's a near-certain event with a range of
consequences," he says, noting
that a relatively small object, less than 200 feet in diameter,
leveled
trees over a 25-mile area in the Tunguska region of Siberia in
1908.
"These things are rare, but over the long haul they are
almost certain to
happen," Clarke says. "That was big enough that if it
hit any major
metropolitan area we would have an unprecedented calamity on our
hands. To
not think about it, or not talk about it, just because it's got
that Star
Wars kind of patina, is a mistake."
Rising to the Occasion
But what really bothers Clarke is that he doesn't hear many
people talking
about it. He thinks that's partly because of a misconception.
Political
leaders seem to think that a catastrophic collision would cause
such panic
in the streets that no amount of planning would be of any help.
Clarke says that's nonsense.
People don't panic during a disaster, he says. Instead, they help
each
other. Way down deep, he says, our society is a civil one, and it
doesn't go
away just because life around us is falling apart.
"Most of us would not rip off our neighbors, or even a
stranger, even if we
knew we would not get caught," Clarke says. "That's
heightened during a time
of disaster."
And it is particularly true when people see themselves as facing
a common
threat.
"They will bind together to fight that threat," he
says.
And in the end, it is the people themselves who must rise to the
occasion.
Clarke points out that the "first responders" in any
disaster aren't police
or firefighters. They are the "people in the street,"
he says, who pull
their fellow citizens from an earthquake-damaged building, or a
crashed
airliner.
Government Secrecy?
So mitigating a major disaster like an asteroid collision will
depend
primarily on how well the people themselves are prepared. They
are the ones,
for example, who will have to help their fellow citizens evacuate
a major
metropolitan area if the asteroid is headed that way. There won't
be enough
cops to do the job.
But nobody can do that without adequate preparation, and the
consequences of
failure could be the loss of thousands of lives that could have
been saved.
My guess is most people figure that scientists will come up with
a plan to
divert the asteroid before it hits the Earth. Some have suggested
that small
rockets placed on the asteroid could push it toward a different
course.
Others have indicated that even painting one side of the big rock
could
cause the solar wind to push it into a safe trajectory. Of how
about a giant
solar sail to pull it out of harm's way?
But that all depends on how much time we have, and whether we
have the
technological resources to do it.
Unfortunately, we're not anywhere close to dealing with the
threat. We don't
even know how to talk about it.
During the recent convention of the American Association for the
Advancement
of Science in Denver, one expert set off a firestorm when he
suggested that
government secrecy might be the best alternative.
Geoffrey Sommer of the Rand Corp., a think tank in Santa Monica,
Calif.,
that advises the federal government on many issues, told a press
conference
that if a planet killer is headed our way, maybe the feds ought
to just keep
their mouths shut.
"If an extinction-type impact is inevitable, then ignorance
for the populace
is bliss," Sommer said.
His comments angered so many people that he has since decided to
decline all
interviews on the subject, according to a Rand spokesman.
Sensitive Politicians
Sommer's plight is worth noting because it reveals just how
contentious this
issue can be. It also shows that it will take a bold leader to
move the
matter forward.
Clarke, for one, isn't optimistic that's going to happen anytime
soon.
"It's hard to see which politicians are going to step up to
the plate," he
says. "They'll be branded as crazies."
Besides, we've got lots of other things to worry about. So we'll
probably
just put this off until some astronomer comes up with an asteroid
that
really is headed our way.
But by then, it will probably be too late.
Lee Dye's column appears weekly on ABCNEWS.com. A former science
writer for
the Los Angeles Times, he now lives in Juneau, Alaska.
Copyright 2003, ABC News