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&section=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



CCCMENU CCC for 2002

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