PLEASE NOTE:
*
CCNet 33/2002 - 11 March 2002
-----------------------------
"Amid the was it or wasn't it debate about the U.S.
recession, a
senior Federal Reserve official has coined a new phrase for the
economic
downturn that began last March, dubbing it: "the Pluto
recession."
Speaking to a group of reporters on Friday, St. Louis Fed
President
William Poole likened the controversy over how to describe the
U.S.
economy's recent woes to the wrangles among astronomers about the
planet Pluto. "The astronomers argue about whether Pluto is
or is not a
planet. It's a marginal object. Some astronomers say Pluto is a
planet and other astronomers say Pluto is not a planet...Any time
you have
an event that is out on the borderline, by definition it's not so
clear."
--Caren Bohan, Reuters
(1) US REMEMBERS 11 SEPTEMBER
BBC News Online, 11 March 2002
(2) THE DISCOVEY OF 2002 EA
Mark Kidger < mrk@ll.iac.es
>
(3) THE DISCOVERY OF 2002 EA: THE FIRST SPANISH NEA DISCOVERY
Rafael Ferrando1 < Rferrand@terra.es
>
(4) COMET IKEYA-ZHANG
Mark Bailey < meb@arm.ac.uk
>
(5) COMET IKEYA-ZHANG CONTINUES TO BRIGHTEN
Sky & Telescope, 6 March 2002
(6) VIEWER'S GUIDE TO NEW COMET IKEYA-ZHANG
Space.com, 8 March 2002
(7) COMET IKEYA-ZHANG PHOTO GALLERY
Spaceweather.com
(8) EARTH SET FOR BRUSH WITH COMET
The Guardian, 11 March 2002
(9) EARTH TO ASH IN A FLASH
Sunday Herald Sun, 10 March 2002
(10) CHANCES OF DYING FROM AN IMPACT
Michael Paine < mpaine@tpgi.com.au
>
(11) UNDERESTIMATING THE IMPACT HAZARD FROM SMALLER NEOs?
Jens Kieffer-Olsen < dstdba@post4.tele.dk
>
(12) AND FINALLY: FED OFFICIAL DUBS US SLUMP THE "PLUTO
RECESSION"
Reuters, 8 March 2002
============
(1) US REMEMBERS 11 SEPTEMBER
>From the BBC News Online, 11 March 2002
http://news.bbc.co.uk/hi/english/world/americas/newsid_1865000/1865988.stm
Three thousand people died in the attacks
The United States is preparing to mark six months since the 11
September
terror attacks with a series of events in New York and
Washington.
In New York, firefighters, survivors and relatives of victims of
the attacks
will gather at the remains of the World Trade Center as two
memorials are
unveiled in remembrance of those who died.
The attacks shocked the world
In Washington, President George W Bush will lead ceremonies at
the White
House, attended by foreign ambassadors and more than 1,000
guests.
Mr Bush will also deliver a speech, outlining the future shape of
the US-led
war on terror.
The commemoration will get under way with a moment of silence in
New York at
0846 local time (1346 GMT) - the exact time hijacked American
Airlines
Flight 11 was deliberately crashed into the north tower of the
trade centre.
A second silence will be held 17 minutes later, in memory of the
moment
United Airlines Flight 175 ploughed into the south tower.
Bell ringing
About 3,000 people lost their lives when the twin towers
collapsed. Many
more died in a similar attack on the Pentagon in Washington and
in a further
hijacked airliner that crashed in rural Pennsylvania.
Despite the destruction, one structure - a 45,000lb (2,041 kg)
sculpture
called The Sphere - survived and will be dedicated to the
victims.
Mayor Giuliani will speak at the ceremony
The steel and bronze design, which had stood in the centre of the
World
Trade Center plaza, will become part of a temporary memorial near
the
remains of the building.
New York Mayor Michael Bloomberg, his predecessor Rudolph
Giuliani, who led
the city through its darkest hour, and New York state Governor
George Pataki
will lead the commemorations in the park, attended by families of
the
victims.
The ceremony will close with the ringing of the bell from the New
York Fire
Department, which lost 343 members who went to rescue people
trapped in the
twin towers.
One of the main events will take place at dusk, when 12-year-old
Valerie
Webb, who lost her father in the attack, will switch on two
powerful beams
of light symbolising the twin towers.
The Tribute of Light will project two 50 foot (15 metre) squares
of light
one mile (1.6 kilometres) skyward and be visible for a radius of
about 20
miles (32km).
The memorials will remain until a final decision is made on a
permanent
tribute to the victims.
'Rogue' states
At the White House, President Bush will reflect on the past six
months and
the fight against terror in an address to victims' relatives,
members of
Congress and other administration officials.
Bush will talk about the fight against terror
White House spokesman Gordon Johndroe said Mr Bush would offer
"a broad
outline of what's been accomplished and where we are headed, the
challenges
we face as the war on terrorism continues".
He said the president would also focus on the importance of the
global
coalition against terror.
Mr Bush is also expected to highlight the danger of
"rogue" nations which
are working to develop weapons of mass destruction.
At the Pentagon, US Defence Secretary Donald Rumsfeld will meet
military
leaders from the coalition and tour reconstruction works six
months after
the building came under attack.
US Vice President Dick Cheney, who is en route to the Middle East
to shore
up support for America's campaign against international
terrorism, will mark
the day of remembrance with UK Prime Minister Tony Blair in
London.
Copyright 2002, BBC
=============
(2) THE DISCOVEY OF 2002 EA
>From Mark Kidger < mrk@ll.iac.es
>
Dear Benny:
Attached is Rafael Ferrando's discovery notes for 2002 EA.
Reading it, I
think that people will agree that it is a splendid demonstration
of just how
well the system handles such discoveries and how astonishingly
fast
everything worked even on a Saturday night.
Another point though is that raised by your correspondent on
March 6th.
Despite the fact that there are astonishingly efficient
programmes such as
LINEAR, NEAT and LONEOS in the northern hemisphere, some objects
of
significant size still slip through the net. In this case the
object has
been discovered only two weeks before a (fairly) close encounter
- although
it is 20 times the distance of the Moon.
As readers will see, this was a pure chance discovery: the object
just
happened to be there passing close to another asteroid that the
astronomer
wanted to observe and Rafael Ferrando just happens to be one of
the few
people who would both recognise a very faint trail (even when it
is pointed
out on the discovery images I can barely see it on my terminal),
realise
that it was a NEO in need of further observation, and be capable
of getting
all the necessary results reduced on-line. This suggests that
there may well
be other asteroids that slip through because they aren't
recognised - maybe
one of your correspondents from the NEO community would like to
comment on
the implications for discovery statistics.
Mark Kidger
=========
(3) THE DISCOVERY OF 2002 EA: THE FIRST SPANISH NEA DISCOVERY
Rafael Ferrando1 < Rferrand@terra.es
>
Observatorio Pla D'Arguines
(IAU Site Code 941)
Castellón, Spain
On March 2nd 2002, as usual on observing nights I prepared to
take exposures
of various comets, supernovae and asteroids with my 12-inch
(30cm) LX-200
telescope and ST9-E CCD. After taking some images of various
comets (P/2001
TU80 (LINEAR-NEAT), C/2002 C2 (LINEAR), and C/2001 C1
(Ikeya-Zhang) and the
supernova Sn 2002ap, I started to take recovery measurements of
asteroids
that have just a few days of observing arc in their first
opposition. This
work is very important because many of these asteroids would be
lost if they
could not be recovered in their second opposition and thus their
orbit would
not be well determined.
The first field that I observed was of 2000 QW65, a main belt
object
observed over an arc of 2 months in 2000. This field also
included two
numbered asteroids: the rather poorly observed 1912 (Annubis) and
the
unnamed asteroid 5480 (1989 YK8).
In this field I noticed a faint trail. Although this might just
have been
noise in the CCD, there was also the chance that it could be a
NEO, so I
took another exposure. When this second exposure appeared I
blinked the two
to see if the mystery object reappeared and if it moved between
them. On
doing this it appeared possible that it could be a NEO, so I took
two more
exposures.
While exposing, I checked the Minor Planet Center (MPC) computer
and
discovered that there is no known NEO in this position. On
finding this, my
heart leapt into my mouth and my pulse raced. Conscious of the
potential
importance of the discovery I took astrometry of the exposures
and sent it
to the MPC. Within seconds the MPC answers asking me to follow
this object
as long as possible as it appears to be a NEO.
The NEO confirmation page at the MPC automatically generated an
announcement
with the positions that I had supplied, requesting other
observatories to
confirm it. At the same time, I contacted my colleague, Pepe
Manteca at
Begues (IAU Site Code 170), and we sent an urgent notification to
the
Spanish language comet observers mailing list called
"Cometas_Obs"
(Cometas_Obs@yahoogroups.com) in the hope that another Spanish
observatory
could confirm it, although bad weather in much of Spain made this
seem
unlikely.
I was able to follow the object from my observatory for almost 5
hours,
although fog and cloud started to appear and made the object
difficult to
observe. As each exposure came off the CCD it was measured and
sent to the
MPC.
The first exposure that showed the object was taken at 21:46UT
and the MPC
was alerted just after 21:51UT. When I had stopped observing -
the last
usable exposure came down from the CCD at 01:12UT - and had sent
off the
last set of measures I could check the NEO Confirmation Page and
saw that
Ondrejov Observatory in the Czech Republic had reported four
measurements
starting at 00:32UT, less than 3 hours after my initial report.
The object
was confirmed. This allowed me to sleep easier because I was in
need of a
few hours rest!
I went to be hoping that the weather would improve and that, on
the Sunday
night I could recover it. However, luck was not with me - it was
cloudy and
I could not observe. That night though observers from all round
the world
could observe, amongst them the Observatorio Astronómico de
Mallorca (OAM),
on the Mediterranean island of Majorca, quite close to my own
observatory
and one of the teams alerted by the mailing the previous night.
With two nights of observations, a provisional orbit could be
calculated and
a designation (2002 EA) assigned. 2002 EA was found to be an
Apollo
asteroid, one that crosses the Earth's orbit and thus one of the
potentially
most dangerous class of NEAs. Given a 15% albedo it would be
about 130
meters across and will pass just behind the Earth in its orbit at
about 8.5
million kilometers distance on March 15th.
1 Aclaratory Note: This text is basically a translation of Rafael
Ferrando's
comments on the discovery. However, I have received full
authorisation from
him to make such changes as seen necessary. These have mostly
involved
adding additional background and details to make the text more
readable
(Mark Kidger).
================
(4) COMET IKEYA-ZHANG
>From Mark Bailey < meb@arm.ac.uk
>
Dear Benny,
Readers of CCNet might be interested to know that we have put a
short
information sheet on the new comet C/2002 C1 (Ikeya-Zhang) on the
Armagh
Observatory web-site ( http://star.arm.ac.uk/ikeya-zhang
). It is now an easy
object with binoculars (at least for those with a good western
horizon),
about magnitude 5.0 when I observed it on Saturday evening. In
other words brightening roughly according to predictions.
Best wishes,
Mark
==============
(5) COMET IKEYA-ZHANG CONTINUES TO BRIGHTEN
>From Sky & Telescope, 6 March 2002
http://skyandtelescope.com/observing/objects/comets/article_477_1.asp
By John E. Bortle
The comet discovered on February 1st by Kaoru Ikeya and Daqing
Zhang not
only seems to have a bright future but possibly a most
interesting past.
Just two days after the comet was first spotted, a similarity was
noticed
between Comet Ikeya-Zhang's preliminary orbital elements and
those of a pair
of much earlier objects (C/1532 R1 and C/1661 C1). Finally, on
February
25th, with 309 astrometric observations in hand, Brian G. Marsden
(Smithsonian Astrophysical Observatory) concluded that this is,
in fact, a
likely return of the comet of 1661.
Ikeya-Zhang's photometric behavior was a topic of much
conversation among
comet observers during mid-February. C/2002 C1 is brightening
rather more
rapidly than expected. The comet's coma appears small, bright,
and tightly
condensed, while the comet itself exhibits a very high gas to
dust ratio.
Such "gas" comets typically brighten more quickly with
their approach to the
Sun than do those with a large dust component.
Because of this, C/2002 C1 could put on a much better show than
most expect;
a peak of magnitude 3.0 would not be at all surprising. The comet
could
potentially unfurl an ion tail 10° to 15° in length as it
sweeps by Earth.
However, the decidedly bluish color of this tail will make it far
more
prominent to the camera than to the eye.
Keep in mind that Comet Ikeya-Zhang will be difficult to locate
low in the
western evening sky after sunset in mid-March. Nevertheless, the
comet is
now visible to the naked eye. Michael Begbie of Zimbabwe writes
that he and
other observers in Poland and Italy spied the comet without
optical aid on
the evening of February 28th. I saw the comet on March 1st (UT)
in 10 x 50
binoculars and, at magnitude 5.5, its brightness was consistent
with
previous observations made over the preceding week. I still
believe the
comet will brighten beyond current predictions.
During the first week of April, the comet skirts north of the Sun
and enters
the morning sky. Skywatchers in the Northern Hemisphere will
likely get
their best views in late April, when the comet makes a slow trek
from
Cassiopeia into Cepheus and then Draco.
The comet reaches its closest point to the Sun (perihelion) on
March 18th.
At that time it will be midway between the orbits of Venus and
Mercury, at
0.51 astronomical unit (76 million kilometers) from the Sun.
The object's dual name recognizes the two comet hunters who first
found it
on February 1st: Kaoru Ikeya of Shizuoka prefecture, Japan, and
Daqing Zhang
in Henan province, China. Zhang described the comet as a small,
8.5-magnitude glow 3 arcminutes across in his 20-cm (8-inch)
reflector.
If the name "Ikeya" rings a bell, it should. Between
1963 and 1967, Kaoru
Ikeya discovered or codiscovered five comets. One of them, Comet
Ikeya-Seki,
was the famous naked-eye Sungrazer of 1965. But little had been
heard from
Ikeya (at least outside Japan) until he made his sixth comet
discovery last
week. "He is the phoenix!" says astrophotographer
Shigemi Numazawa of
Niigata, who adds that Ikeya, now age 58, manages the Ikeya
Optical Lab, a
supplier of telescope mirrors to Japan's discriminating
observers.
- - - - - - -
John Bortle is a well-known comet expert and an authority on
comet observing
throughout history. His Web article "The Bright Comet
Chronicles" provides
brief accounts of all those comets seen between 1800 and 1997
which attained
an observed maximum brightness of +2 or greater.
Copyright 2002 Sky Publishing Corp.
==============
(6) VIEWER'S GUIDE TO NEW COMET IKEYA-ZHANG
>From Space.com, 8 March 2002
http://www.space.com/spacewatch/spacewatch_comet_020309.html
By Joe Rao
A big question for skywatchers during the next couple of months
is how
bright the newly discovered comet, Ikeya-Zhang, will become. The
answer
can't be accurately predicted, but this much is nearly certain:
The comet
will provide an opportunity that comes along just once or twice
per decade.
Comet Ikeya-Zhang will make its closest approach to the Sun on
March 18,
when it will be roughly 47 million miles away or midway between
the orbits
of Mercury and Venus. Shortly after it was discovered on Feb. 1,
it appeared
there was a chance that Ikeya-Zhang might evolve into the comet
of the
decade, judging by an initial rapid brightening and its possible
link to a
spectacular 16th Century comet.
Observations of the comet in recent days however, have tempered
those
initial high expectations.
Currently, Ikeya-Zhang appears in binoculars and small telescopes
with a
faint and somewhat distorted bluish gas tail about 5 degrees long
accompanying a sharp, well-condensed head of about fifth
magnitude.
Dimly visible
Ikeya-Zhang might eventually get as bright as third magnitude,
meaning that
it should be at least dimly visible to the naked eye in dark
skies, though
better seen in binoculars or telescopes. That kind of brightness
would still
make Ikeya-Zhang a very fine comet from the viewpoint of an
amateur
astronomer, especially in April, when it will be approaching the
Earth and
become well placed high in a dark sky.
But at the time of this article's publication, it doesn't appear
that this
comet will become the kind of spectacle that comet Hale-Bopp was
in grabbing
the public's attention in 1997.
However, regardless of what script we write here for
Ikeya-Zhang's
performance, be advised that comets are notoriously bad actors.
Few
celestial events have greater false-alarm potential than the
interplanetary
vagabonds we call comets.
Earlier this winter, for example, comet LINEAR WM1 briefly and
unexpectedly
flared-up, becoming as bright as third magnitude, though visible
only from
the Southern Hemisphere. Comet Ikeya-Zhang could brighten
similarly and
provide a real surprise.
Ancient visitor returns
Soon after a preliminary orbit was calculated for Ikeya-Zhang,
some orbital
experts, lead by Syuichi Nakano of Japan, noticed a similarity to
a pair of
much earlier comets that appeared in 1532 and 1661.
The 1532 comet, in particular, was a strikingly bright comet,
according to
Oriental records. Curiously, during the first week or two that
Ikeya-Zhang
was under careful scrutiny by observers worldwide it appeared to
be
brightening at an unusually rapid pace. Perhaps, some thought,
this was
going to be the return of the great comet of 1532.
Excitement began to build with the prospects of a potentially
spectacular
comet gracing the late winter and early spring skies.
But then, during late February, Ikeya-Zhang's brightening
noticeably slowed.
A more recent orbital computation by Brian Marsden of the
Smithsonian
Astrophysical Observatory in Cambridge, Massachusetts, now
suggests
Ikeya-Zhang may be a return of the 1661 comet, not the one from
1532. This
is a come-down of sorts for skywatchers, since historical records
suggest
the 1661 was a middle-of-the-road performer.
Interestingly, this is not the first time that these same two
comets were
embroiled in an identity crisis. In the late 17th Century, Sir
Edmond Halley
-- the same man for whom the most famous comet is named --
compared the
apparent similarities of the orbits of the comets of 1532 and
1661 as part
of his own comet studies. He became convinced that they were one
in the
same, even implying that there would be a return of the comet in
1790.
What Ikeya-Zhang might look like
Joannes Hevelius of Gdansk, Poland, observed and wrote
extensively about the
1661 comet in his 1668 tome, "Cometographia." He went
on to report that the
nucleus, or head, of the 1661 comet displayed "multiple
structure," as seen
in his crude telescope. Rather than seeing the break-up of the
comet
nucleus, which can cause a comet to brighten suddenly, Hevelius
might have
been observing a series of bright jets of material being expelled
from the
comet head.
The 1661 comet also displayed a tail that measured 6 degrees in
length (for
comparison, 10 degrees is roughly equal to the width of your fist
held at
arm's length).
These descriptions may help to provide clues as to how comet
Ikeya-Zhang may
appear to us in the coming weeks. One important difference,
however, is that
the 1661 comet headed directly away from the Earth after sweeping
closest to
the Sun (a point called "perihelion") and quickly faded
away. But
Ikeya-Zhang will be approaching the Earth for a number of weeks
following
its perihelion and thus should remain visible for a much longer
stretch of
time.
If the 1661 comet and Ikeya-Zhang are indeed the same, it would
set a record
of sorts: the longest amount of time that has elapsed between the
discovery
of a comet and a definitive sighting upon its return to the inner
solar
system.
The current record is held by comet Herschel-Rigollet, discovered
by
Caroline Herschel in 1788 and rediscovered 151 years later by
Roger
Rigollet, in 1939. Comets with orbital periods of 200 years or
less are
considered "short period" comets. If Ikeya Zhang is the
1661 comet, this
would be the very first time that the return of a "long
period" comet, with
an orbital period greater than 200 years, has ever been observed
and noted
as such.
The 1661 comet might have reached the far end of its cigar-shaped
elliptical
orbit around the year 1830, when it was probably more than 9
billion miles
from the Sun -- more than twice as far away as Pluto. If so, then
ever since
it has been on a slow, steady course taking it back toward the
Sun, finally
to reach its closest point again on March 18.
Copyright 2002, Space.com
=============
(7) COMET IKEYA-ZHANG PHOTO GALLERY
Spaceweather.com
http://www.spaceweather.com/comets/gallery_iz.html
=========
(8) EARTH SET FOR BRUSH WITH COMET
>From The Guardian, 11 March 2002
http://www.guardian.co.uk/uk_news/story/0,3604,665361,00.html
A comet discovered by astronomers this year and heading past the
Earth will
be bright enough to see with the naked eye later this month.
Comet Ikeya-Zhang, named after the Japanese and Chinese
astronomers who
first spotted it on February 1, will be the brightest comet to
make an
appearance since Hale-Bopp in 1997.
During the second half of this month and the first half of April
it will
brighten rapidly to a point where, under good conditions, it
should be
visible to the naked eye as a faint smudge in the western sky.
Town dwellers will have a harder job seeing it than people in the
countryside, but a low-powered pair of binoculars should provide
a much
clearer view.
Robin Scagell, from the Society for Popular Astronomy, said the
comet, which
looks like a slightly hazy star with a bright tail, was already
visible. "I
was looking at it last night. It's not amazingly bright at the
moment. Some
people have seen it with the naked eye. But it should get
brighter over the
next few weeks.
"The comet has a pronounced tail extending over five to 10
degrees, which is
about 10 times as long as the width of the moon."
Ikeya-Zhang is a periodic comet, which means it returns to the
inner solar
system on a regular basis.
It would have been visible in 1661 and may also have been seen in
1273 and
877. Some calculations suggest that on a previous occasion it
might have
split in two, with the larger fragment returning in 1532.
The comet can be found by looking low in the western sky between
about
7.15pm in early March and as late as 9pm by the first week of
April.
It will travel in an arc through the faint constellation of
Pisces, and can
best be seen by looking to the left of the easier-to-identify
Pegasus star
pattern. By March 16 it will be below the constellation of Aries.
In ideal conditions looking through binoculars it may be possible
to see two
separate tails, a bright one caused by dust from the comet and a
fainter
bluer one created by gas.
Mr Scagell said there was no need to worry about Ikeya-Zhang
hitting the
Earth - it will miss us by a comfortable 37m miles.
Copyright 2002, The Guardian
==============
(9) EARTH TO ASH IN A FLASH
>From Sunday Herald Sun, 10 March 2002
http://www.sun-herald.com/
GRAEME O'NEILL
COMETS and asteroids are making a splash, with news emerging of
plans to
land a probe on a celestial rock in 2011 and research projects
throwing
light on a catastrophic collision 64.8 million years ago.
Chicxulub, on Mexico's Yucatan peninsula, was Ground Zero for the
greatest
cataclysm of the past 200 million years.
At literally astronomical odds, an asteroid or comet looping
around the Sun
intersected the Earth's orbit at a velocity of 110,000 km/h.
The mountain-sized object would have taken only four seconds to
punch
through the stratosphere.
The Hollywood special effects sequences of enormous, fiery rocks
tearing
across the sky seen in the Deep Impact blockbuster did not quite
convey the
speed and magnitude of the spectacle.
Too small, too slow, and the Big One probably came in
near-vertically, not
at a shallow angle.
It slammed into the shallow Caribbean Sea, vaporising the water
and the
limestone sea bed, then melting or pulverising the underlying
oceanic rocks
to a depth of 7km.
A tidal wave, initially about 5km high, spread out at supersonic
speed from
the impact zone, and surged 200km inland.
It pulverised the nearby coastal zones of North and South
America, and
traversed the then-narrow Atlantic seaway to devastate the
western coast of
Europe and Africa.
A 2000km/h shock wave ripped through the lower atmosphere,
momentarily
heating it to 2500C, and causing gaseous nitrogen to react with
the hydrogen
and oxygen in water vapour, forming nitric acid.
For months afterwards the Earth's surface was deluged by a hard,
acid rain
that changed the chemistry of lakes and waterways, caused marine
food chains
to collapse.
The blast spawned an environmental holocaust that extinguished at
least 70
per cent of the world's animal and plant species, including the
dinosaurs.
It left a huge circular scar centred on Chicxulub.
The initial crater was probably no more than 100km in diameter,
but it
widened as its steep edges collapsed.
Beyond the crater, fracture lines radiated out to a diameter of
almost
300km. It remains a mystery as to whether the extraterrestrial
assassin was
a large, icy comet about 15-17km in diameter, or a smaller, rocky
asteroid
7km to 10km wide.
A drilling project near the village of Merida, on the Yucatan
peninsula, may
resolve the issue.
The $3 million Chicxulub Scientific Drilling Project is a joint
Mexican-US
operation, led by the geologists from the National Autonomous
University of
Mexico, and involving researchers from the University of Arizona.
Late last month, the drilling project was proceeding at a rate of
almost 50
metres a day and was rapidly approaching its target depth of
1.8km.
Things have come full circle at Chicxulub. It was during a
routine an
oil-drilling survey in the 1930s that geologists first
encountered strange
minerals and structures in the rocks.
The anomalies remained a mystery until 1991, more than a decade
after Nobel
laureate physicist Luis Alvarez and his geologist son Walter
proposed that a
thin layer of clay found in rocks in a mountainous area near
Gubbio, Italy,
represented the global fallout from an extraterrestrial impact
that wiped
out the dinosaurs.
Most of their peers dismissed the theory as outrageous, but
satellite images
confirmed the presence of an enormous, circular structure beneath
the
Yucatan peninsula. It is betrayed by the presence of a huge,
circular
arrangement of wells, locally called cenotes, formed when
limestone caves
collapsed and were filled by rain.
The immediate cause of the extinctions at the end of the
Cretaceous period
is now known beyond reasonable doubt: an asteroid or comet
impact.
But what happened after the impact to cause the global wave of
plant and
animal extinctions has been the subject of much debate. Some
scientists
think the extinctions were caused by an "asteroid
winter", as fine dust
pulverised by the impact spread through the stratosphere,
blocking out
sunlight.
In the resulting deep-freeze conditions, plant photosynthesis
would have
halted, severely disrupting food chains.
But there may have been few plants left to photosynthsise.
Black, sooty fallout mixed with the fine, greenish clay that
marks the end
of the so-called Cretaceous-Tertiary (K-T) period at sites such
as Stevns
Klint in Denmark, attests to a firestorm, ignited by the intense
heat of the
passing shock wave, and a rain of incandescent droplets of glassy
material
that condensed from vaporised minerals.
Rounded, glassy particles called spherules are abundant in the
K-T layer.
Soot deposits have been found in the K-T layer at sites across
the world,
including in New Zealand, which is almost as far away from from
Stevn's
Klint and Chicxulub as it is possible to be.
The conflagration was clearly global in extent, and caused most
of the
world's forests to burn down.
A paper published in the February 22 edition of Science chills
the "asteroid
winter" theory with an analysis of the pulverised rock
thrown into the
atmosphere by the Chicxulub impact.
US geologist Kevin Pope has studied the size of particles thrown
up when the
comet or asteroid hit Earth.
The heaviest were great boulders weighing 40 tonnes that rained
down several
hundred kilometres from the crater.
They formed a geological feature called the Big Boulder Bed,
exposed on
eroded hillsides on the Caribbean island of Haiti.
The finest particles, and the last to rain down out of the
atmosphere,
formed a layer about 3mm thick on top of the K-T layer.
The largest particles in this thin layer are shattered quartz
grains about
0.005mm in diameter.
DR Pope's analysis showed that the number of larger particles
dropped off
sharply as the distance from the crater increased. It was as if
they had
dropped from relatively nearby clouds, rather than being blasted
into the
stratosphere and spread around the globe.
Dr Pope also found that there were not enough of the smallest
particles to
have blocked out sunlight.
The light level would have been similar to that seen on a dull
winter's day
in Seattle rather than that experienced in the depths of a
Scandinavian
winter.
The concentration of atmospheric dust, in short, would have been
100 to 1000
times less than that needed to halt photosynthesis.
Undoubtedly, it reduced photosynthesis, but the real culprit is
more likely
to have been the sudden loss of most of the world's vegetation in
the
firestorm that immediately followed the impact, and the effect of
the global
pall of dense smoke on light levels at the Earth's surface.
Further insights into the chemistry and structure of comets
should be gained
when a European spacecraft attempts to land a probe on one in
2011.
The European Space Agency's Rosetta probe will chase the 1km-wide
Comet
Wirtanen as it accelerates towards the Sun, and will release a
probe that,
with luck, will land on the surface.
Comet Wirtanen is a pipsqueak compared with the source of the K-T
impact.
It is a sobering thought that the impact of a 1km-wide comet
anywhere on
Earth today would bring civilisation to its knees.
Try to imagine, then, the destructive power of the object that
came down in
the Caribbean 64.8 million years ago.
Copyright 2002, Sunday Herald Sun
============================
* LETTERS TO THE MODERATOR *
============================
(10) CHANCES OF DYING FROM AN IMPACT
>From Michael Paine < mpaine@tpgi.com.au
>
Dear Benny
I am puzzled by the apparent quote from Al Harris that the
chances of dying
from an asteroid impact are about one in a million. In the early
1990s,
Morrison and Chapman estimated 1 in 20,000 (~3,000 fatalities per
year) and
estimates of risk have changed little since then. The estimated
number of
1km+ NEAs (note A for asteroid - comets are not included) has
reduced by
perhaps half and the number of undetected 1km+ NEAs is now
perhaps one
quarter of the M and C estimates (assuming the US Spaceguard
program is at
the halfway point). This suggests the chances have
"improved" to about 1 in
80,000. One the other hand, this assumes that all of the risk is
due to 1km+
asteroids. More recent work has highlighted the risk from smaller
objects
and from comets.
For example a one million year simulation that I conducted with
John Lewis's
HAZARDS software
( http://www4.tpg.com.au/users/tps-seti/sta1046.htm
) came up with an average
annual death toll of 7500. Of these only about 3000 were due to
1km+
asteroids that are targetted by US Spaceguard.
3000 were due to one (unlucky) comet impact and the remaining
1500 were due
to sub-1km impactors. That simulation assumed there was no
Spaceguard
program. We can (very roughly) estimate the benefits of a
US-style
Spaceguard program by applying the estimated
"completeness" after 10 years:
Impactor Annual Completeness Revised
Fatalities after 10 yrs
Annual Fatalities
Asteroid <200m 500 2% 500
Asteroid 200m to 500m 500 30% 300
Asteroid 500m to 1km 600 50% 300
Asteroid 1km+ 3000 90% 300
Comet (usually 1km+) 3000? <1%? 3000
----
----
7600
4400
This is on the basis that the Spaceguard program does not
actually find a
NEA that will impact the Earth but simply reduces the magnitude
of the
threat through elimination of 90% of 1km+ NEAs and a minor
proportion of
smaller NEAs as potential impactors.
For comparison, the worldwide fatalities from earthquakes,
averaged over
many decades, is about 10,000 per year and that from commerical
airliner
crashes is about 700 per year (but, of course, a typical US
citizen is
exposed to greater risk of dying in a plane crash than most of
the rest
of the world).
Based on Ted Bryant's book, the death toll from from tsunami
(probably NOT
impact generated) works out at about 300 per year over the past
2000 years.
These are interesting statistics that rank that NEO threat
against other
causes of death. However, they don't get across the point that
NEO impacts
are probably the only natural disaster that could bring down our
global
civilisation. Since they are predictable and, to some extent,
preventable, it would be grossly negligent for our generation to
not take
steps to try and reduce the risk.
regards
Michael Paine
=====================
(11) UNDERESTIMATING THE IMPACT HAZARD FROM SMALLER NEOs?
>From Jens Kieffer-Olsen < dstdba@post4.tele.dk >
"My real worry is that too many people will get frantic
about the
impact hazard. ... I actually think we're doing about as much as
we
should."
--Alan Harris, 27 February 2002
Dear Benny Peiser
You probably highlighted THE sentence from the Williams article.
The suspicion that one could be forgiven for harbouring is that
the
medium-size NEO impact risk is a hush-hush area, which is being
addressed in
Keyhole-context rather than in the public domain.
Let's consider the three categories of impact from a US point of
view:
1. The larger-than-1km objects have a global impact. The world
MUST react if
at all possible, and there will be unanimous backing in the UN to
any
undertaking the USA might offer. The discovery
of an asteroid due to impact half a century or so from now will
be a boost
to American industry and morale. Go get it!
2. The smaller-than-300m objects cause severe damage locally.
Odds are that
the US will not be hit first time, and even if the impact DID
take place in
the United States the country will preserve its international
position and recover.
Business as usual!
3. The regional disasters caused by medium-sized objects NEED to
be avoided
at all costs, if North America is the target area. - But would it
justify
the gigantic cost and efforts, if bound to destroy say Australia?
Top-secret!
Let's be optimistic and work hard to ensure that the 10,000 or so
category 3
objects will be mapped in an OPEN program, which must be
initiated well
before the mapping of category 1 objects is deemed complete and
funds correspondingly
reduced.
Subscribers to CCNet will undoubtedly agree that it is also
cost-justified
to keep tabs on category 2 objects, but let's face the sad fact
that it will
take several decades at least to build up the political will for
funding
such an endeavour.
Yours sincerely
Jens Kieffer-Olsen, M.Sc.(Elec.Eng.)
Slagelse, Denmark
=================
(12) AND FINALLY: FED OFFICIAL DUBS US SLUMP THE "PLUTO
RECESSION"
>From Reuters, 8 March 2002
http://biz.yahoo.com/rf/020308/n08133388_1.html
By Caren Bohan
ST. LOUIS, March 8 (Reuters) - Amid the was it or wasn't it
debate about the
U.S. recession, a senior Federal Reserve official has coined a
new phrase
for the economic downturn that began last March, dubbing it:
``the Pluto
recession.''
Speaking to a group of reporters on Friday, St. Louis Fed
President William
Poole likened the controversy over how to describe the U.S.
economy's recent
woes to the wrangles among astronomers about the planet Pluto.
``The astronomers argue about whether Pluto is or is not a
planet,'' Poole
said. ``It's a marginal object. Some astronomers say Pluto is a
planet and
other astronomers say Pluto is not a planet...Any time you have
an event
that is out on the borderline, by definition it's not so clear.''
Tiny, cold Pluto, the smallest and most distant planet in the
solar system,
has been the subject of frequent astronomical debate with an
attempt as
recently as 1999 to reclassify it as asteroid No. 10,000.
Because of the similarities in the debates, Poole said, ``I think
we're
going to end up calling this the Pluto recession.''
The National Bureau of Economic Research, an elite private group
that is
viewed by most economists as the arbiter of U.S. business cycles,
has
declared that a recession started in March of last year.
Even though the economic numbers have brightened lately, NBER has
not yet
ruled on when the recession ended.
In the meantime, however, recent data on U.S. gross domestic
product show
that GDP only experienced one quarter of contraction, a drop of
1.3 percent
in the third quarter of 2001. GDP, regarded as the broadest gauge
of
national economic activity, in both the second and fourth
quarters of last
year was positive, although in the second quarter it was only
marginally in
the plus column, up 0.3 percent.
That puts the NBER -- which uses a broader set of indicators that
does not
include GDP -- at odds with the short-hand definition used by
some
economists of a recession as two straight quarters of falling
output.
That has prompted some private economists as well as a few
officials in the
Bush administration to question whether a recession really
occurred.
Still another group of economists are willing to give the NBER
the benefit
of the doubt, but are using words like ``recessionette'' and
``mini-recession'' to describe the recent economic episode in
which 1.4
million people lost jobs.
Poole, who spent his career as an academic economist before
joining the Fed,
said that when the dust settles, he'll side with whatever call
the NBER
makes.
``Whatever I say -- it is or isn't -- it's going to go down in
history as
what the National Bureau says it is,'' Poole said.
Copyright 2002, Reuters
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