CCNet 127/2000 - 6 December 2000

"Last month's warning that a 25,000-ton asteroid could strike Earth
in 2030 sounded pretty scary. Until the International Astronomical Union
(IAU) "ruled out" the collision two days after issuing the warning.
Weeks later, official uncertainty still reigns over whether the
rock, asteroid 2000 SG344, exists. Instead, a very bright piece of a 1971
Saturn rocket booster may have misled astronomers into thinking it was a
much larger object. Similar warnings, and retractions, have increasingly
made headlines. And astronomers, pushed by such scares -- with two
coming just this year -- are rethinking how they release such news and
even which asteroids they should worry about."
    -- Dan Vergano, USA TODAY, 5 December 2000

    USA Today, 5 December 2000

    USA Today, 5 December 2000

    The Columbus Dispatch, 5 December 2000

    The Times, 5 December 2000

    Ron Baalke <>

    Jacqueline Mitton <>

    Michael Paine <>

    Andrew Glikson <>

    Jon Richfield <>

     Neil Bone <>


From USA Today, 5 December 2000

By Dan Vergano

Last month's warning that a 25,000-ton asteroid could strike Earth in 2030
sounded pretty scary.

Until the International Astronomical Union (IAU) "ruled out" the collision
two days after issuing the warning.

Weeks later, official uncertainty still reigns over whether the rock,
asteroid 2000 SG344, exists. Instead, a very bright piece of a 1971 Saturn
rocket booster may have misled astronomers into thinking it was a much
larger object.

Similar warnings, and retractions, have increasingly made headlines. And
astronomers, pushed by such scares -- with two coming just this year -- are
rethinking how they release such news and even which asteroids they should
worry about.

"The alerts are a reflection of our new perception of the threat," says
astronomer David Jewitt of the University of Hawaii. "Before now, these
objects whizzed past without us knowing or caring."

Using a new scale

The IAU's November announcement initially warned of an object 100 to 230
feet in diameter with a "low probability" of hitting Earth. And SG344
enjoyed 500-to-1 odds of turning out to be a miss, making it a 1 (out of 10)
on something called the Torino Scale.

Unveiled by NASA last year, the scale represents the space counterpart to
the earthquake-measuring Richter scale. And the problem, some astronomers
say, is that while everyone knows that a 1 on the Richter scale doesn't mean
the sky is falling, not enough people know the same holds true for the
Torino Scale.

The scale, developed by astronomer Richard Binzel of MIT, assigns a number
to each asteroid or comet 65 feet or more in diameter that travels near
Earth as soon as it is spotted. The number indicates the likelihood of
collision and the damage potential and runs from 0 to 10.

Most ratings from 1 to 7 will be reassigned to 0 after the first alert, when
further measurements come in, Binzel says. Few will ever become an 8, 9 or
10, representing certain collision. As a general rule, some astronomers
suggest, the Torino number corresponds to the number of newspaper columns
that the alarm deserves.

"If we could have done (the SG344 announcement) again, we would have waited
one more day," says astronomer David Morrison of NASA's Ames Research Center
in Moffett Field, Calif. He heads the IAU committee on "near-Earth objects."

Ideally, the IAU and other astronomy organizations would learn of a possibly
dangerous object from an astronomer and then spend 72 hours verifying it
before issuing a Torino Scale alert. Such was the case for SG344, but better
data came in just after the deadline -- created because astronomers say they
don't want to cry wolf about asteroids but also don't want to seem to be
keeping secrets.

"It's important that the scientific community is seen not to be involved in
any sort of cover-up," says meteorite scientist Matthew Genge of London's
Natural History Museum.

Also, he says, it's important "that inherent observational difficulties are
not seen as incompetence or as a mistake."

Still searching the skies

Such difficulties exist because scientists, and governments, still haven't
completed a sky survey of near-Earth objects. Most estimate the number of
globally dangerous objects, ones that would rate a 10 on the Torino Scale if
they were aimed at us, at between 700 to 1,200 in orbits near Earth. "Near"
to astronomers means the object's closest approach to the sun is within 30
million miles of Earth's orbit.

A NASA effort to find 90% of space objects about 1 kilometer (0.62 mile) in
width, the ones deemed globally dangerous, won't be completed by a 2008
deadline, "but we'll be close," Morrison says. A 1994 estimate in the
journal Nature reckoned that collision with any one of those could lead to
1.5 billion deaths.

Astronomers rate the chances of a global-damage-type collision at less than
1 in 1,000 over the next 100 years. By comparison, National Center for
Health Statistics figures give a person 28,000-to-1 odds of being killed by
lightning in that time. The United Kingdom's Task Force on Near-Earth
Objects released a September report that rules such a collision out in the
next 50 years. But alarms and retractions likely will figure in headlines
for years to come, Jewitt says. "Impacts are a statistical certainty, and
it's just a matter of time before a big one will hit."

Copyright 2000, USA Today


"Most ratings [on the Torino Scale] from 1 to 7 will be reassigned to 0
after the first alert, when further measurements come in, [Richard] Binzel
says." I agree: this is an accurate description of past asteroid scares and
the possibility of further premature impact announcements in the future. In
an article ("Impact Scares and how to avoid them", Astronomy Now, January
2001), I emphasis precisely this inherent flaw of the Torino Scale which
could easily trigger real mass hysteria: "In fact, we could in the future
have cases of objects reaching Torino level 6 or 7 (presumably with the
associated worry to the public), before plummeting to zero as soon as extra
data allow the object's orbit to be calculated more precisely."

Given that we just suffered the consequences of yet another false impact
alert (which was due to a *tiny* space object that might not even be an
asteroid), can you imagine what would happen with a Torino level 7
announcement which, eventually, would be "reassigned to 0 after the first
alert"? If not, let me tell you what a level 7 announcement would read like:

Torino Scale level 7: "A close encounter, with an extremely
significant threat of a collision capable of causing a global

Is that really what we want to publish - knowing full well that further data
will almost certainly eliminate the announced apocalypse? As Richard rightly
says, we could indeed have such a scenario at any time. Given the short arcs
of newsly discovered PHAs, you could theoretically calculate premature
impact predictions in thousands of them! As far as I am concerned, it has
become obvious that the current the IAU guidelines regarding the
announcement of impact predictions are totally inadequate if we want to
prevent the repetition of false and premature asteroid scares. Unless they
are revised accordingly, the public will increasingly hold the NEO community
responsible for any future fiascos.  BJP


From USA Today, 5 December 2000

Collision fears have built for 40 years

Modern concern about asteroids began with geologist Eugene Shoemaker's 1960
suggestion that craters on Earth resulted from such collisions.

Over time, and with the highly visible 1994 crash of a comet into Jupiter,
concern grew higher.

Hollywood chipped in with two impact movies in 1998, Armageddon and Deep
Impact, raising public awareness of something scientists call a real danger.

A 1992 NASA report deemed space objects 1 kilometer (0.62 mile) or larger in
diameter to be a global threat.

Something that size smacking into the planet may have ended the age of the

Calculating future impacts represents a bit of a challenge for astronomers.
Theoretically, one can calculate the orbit of Earth and that of a nearby
object, if its speed and position are known with some accuracy, to see
whether a date exists on which the two will meet. But such a calculation
ignores the subtle gravitational tugs on both bodies caused by other solar
system objects, some unknown and some very small, which perturb orbits after
only a few decades, making them unreliable. Further, new data on an asteroid
or comet can alter the trajectory first plotted for it. For those reasons,
astronomers often can give only the odds of a collision rather than a
yes-or-no impact announcement.

In 1932, astronomers spotted Apollo, the first "potentially hazardous
asteroid" (PHA), one larger than 600 feet in diameter that passes within 5
million miles of Earth. The find triggered a small scientific sensation, but
astronomers lost track of the object shortly afterward. As of December, 278
PHAs fill the registry at the Harvard-Smithsonian Center for Astrophysics.

If any near-Earth object ever does appear headed toward Earth, astronomers
hope to have enough warning so that some space mission could deflect the
object years ahead of its impact. Current thinking focuses on using nuclear
bombs to alter the path via a detonation some distance from the object.
Copyright 2000, USAToday


From The Columbus Dispatch, 5 December 2000

Microbes in Antarctic ice could point to life in space OSU researcher ready
to study on cold continent

David Lore
Dispatch Science Reporter

Brent Christner is packing for Antarctica as part of an Ohio State
University study of life forms that survive even when seemingly frozen

The research is for his doctoral thesis, OSU's first on the biological basis
for thinking there might be life on other planets.

"I always thought, even before I came to Ohio State, that Antarctica would
be a neat place to go to,'' said Christner, 30, a graduate student in the
Department of Microbiology.

He soon discovered that most of the scientists the National Science
Foundation sponsors on the cold continent are there to study rocks and ice
formations rather than microbes.

"But that's about to change,'' Christner said. "The work people are doing
down there shows this isn't just a frozen, dormant area. It's a place where
life exists -- life is there -- and the search for other places where life
exists in our solar system is now driving this kind of research.''

The road to space goes through Antarctica because conditions there are the
closest on Earth to conditions on Mars and the Jovian moon Europa, two
celestial bodies that might have enough liquid water to support life.

Since 1997, Christner and microbiology Chairman John N. Reeve have been
consulting with the National Aeronautics and Space Administration on a
sample-gathering mission to Europa sometime after 2008.

"They want our experience in terms of melting ice in a way that retains any
biological activity,'' Reeve said.

Since the Europa mission would most likely be a one-way, five-year trip,
NASA is designing a probe to pierce the planet's thick ice, sample its
contents and then radio findings back to Earth.

Astrobiology -- the study of life in the universe -- is now considered solid
science rather than science fiction, Reeve said. 

"That reflects a change in its general acceptance. A decade ago, if you
asked most microbiologists about the prospects for extraterrestrial life,
they wouldn't have taken you seriously.''

Christner will be working out of the U.S. McMurdo scientific station during
January and February, collecting and analyzing ice samples for evidence of
life forms such as bacteria, yeasts and fungi. He will be one of 24 students
from across the nation at McMurdo for a workshop on biological diversity.

Since coming to Ohio State from the University of Dayton in 1997, Christner
has worked with Reeve, his academic adviser, to identify life forms in core
samples recovered by other scientists from Antarctica and mountain glaciers.

After graduation, Christner plans to return to Antarctica in 2002 with a
core-drilling team being organized to explore a subglacial lake near the
South Pole.

The cores analyzed so far, including some 750,000-year-old Chinese ice
drilled by OSU glaciologist Lonnie Thompson, were found to contain
still-living bacteria capable of being revived in the laboratory.

NASA scientists announced in October that they had revived bacteria that had
been dormant in salt crystals for more than 250 million years.

"In solid ice, no life processes are possible, but solid ice is not that
solid,'' Christner explained. There are always fractures and pockets in the
ice where liquid water -- and inevitably bacteria -- collect.

"Most of the things we find are very tough bacteria,'' usually blown onto
the ice by the winds, he said. "They're highly resistant to all kinds of
environmental stress.''

The OSU study is being financed from a four-year, $340,000 National Science
Foundation grant.

Copyright 2000, The Columbus Dispatch


From The Times, 5 December 2000,,46244,00.html 
Comets a possible source of BSE?

Letter to the Editor
Sir, Diseases of plants and animals have a long history of mysterious
appearances without any satisfactory explanation being offered of where they
have come from. An example some years ago was the lethal respiratory disease
that hit grey seals in the remote Siberian Lake Baikal.

Life on Earth is far too intricate to have evolved here in isolation from
the rest of the Universe. Recent studies have shown that much of the
material escaping from comets is in the form of organic particles that
cannot be distinguished from biomaterial. The input to the Earth is
estimated to be several tens of tonnes of cometary material per day,
sufficient, if it was all in the form of bacteria, to give a daily incidence
of several hundred thousand bacteria per square metre of area. For the most
part the material simply washes away. But, in rare cases, a connection may
occur and if this escalates a new disease can be born.

Small particles of bacterial and viral sizes descend through the Earth's
stratosphere mostly during the winter months, and we believe that the nearly
unique English and Welsh practice of out-wintering cattle explains why BSE
hit English and Welsh farms more severely than elsewhere. English and Welsh
farmers move cattle frequently from field to field, maximising their chance
of picking up any pathogen that may fall during the winter months from the
air onto the grass. Once a causative agent (genetic fragment or piece of
infective protein) got into a few cattle man took a hand, by grinding up
infected animals and including them in feed for more cattle.

We live nowadays in a blame culture, but in our view there was no culprit,
not unless blame be equated with ignorance. Indeed the political
authorities, by banning the inclusion of infected portions of cattle in
cattle feed, may be said to have acted both quickly and responsibly.

Whether they should also have banned any use of cattle products in medical
vaccines remains another question with disturbing possibilities.

Yours faithfully,

24 Llwynypia Road,
Lisvane, Cardiff CF14 0SY.
December 1.


From Ron Baalke <>

From Concord Monitor Online, 5 December 2000

Visitor from space blamed in field fire

Residents say meteorite landed in yard
Tuesday, December 5, 2000

Monitor staff

SALISBURY - The scene was quiet by the time Salisbury firefighters got
there. Neighbors had doused the backyard fire that had prompted the call,
and the meteorite that had started the ground fire had stopped blazing.

Yes, a meteorite.

At least that's what residents report.

Salisbury's extraterrestrial visitor slammed into the backyard of 129
Hensmith Road a little after 5 p.m. yesterday, according to witnesses,
burying itself in the ground and starting a small fire.

Stunned residents described the falling ball of fire to Fire Chief Edwin

"When we got there they told me they saw this meteorite come in," Bowne
said. "I've been doing this for 30 years. I've never seen anything like it

He said the falling rock had started a flame that burned about an 18-inch
area, and that the ground was muddy from residents pouring buckets of water
on the small fire.

"It's there," he said. "Buried in the mud."

The New England Meteoritical Services reports that the recovered mass of
meteorites is some of the scarcest material on Earth, much sought after by
researchers and collectors.

So, it's not so surprising that this was a first for New Hampshire fire

"It's a little weird for my book," said the fire dispatcher who dealt with
the call. "I've never had anything drop out of the sky on my watch."

He said the National Weather Service, which he called for advice, didn't
know what to do about the meteoritic visitor either.

"They said, 'We just predict the weather; we don't predict stuff falling out
of the sky.' "

According to the New England Meteoritical Services, meteorites are
essentially shooting stars that make it to the ground. The majority, it
reports on its Web site, originate from asteroids that have shattered. A
smaller number come from the moon, comets or the planet Mars.

"It's so weird," the dispatcher said. "That's all I can say."

The owner of the landing site could not be reached for comment last night.

Other residents on the street said they had heard or seen the fire trucks,
but did not get a glimpse of the meteorite itself. And given their
inexperience with visits from outer space, some of these residents may have
been just a teensy bit skeptical.

"I know we're a good place to land in," said Peter Merkes, a Hensmith

As for the meteoritic cause of the fire?

"Sounds like a great excuse," said resident Jerry Lorden with a laugh.

Copyright 2000, Concord Monitor

From Jacqueline Mitton <>

Royal Astronomical Society
Press Notice

Date: 4 December 2000         For immediate release

Ref. PN 00/22

Issued by:
Dr Jacqueline Mitton, RAS Press Officer
Office & home phone: Cambridge ((0)1223) 564914
FAX: Cambridge ((0)1223) 572892

RAS web:

* * * * * * * * * * *
Contact for this release:

Prof. Sandra C. Chapman
Space and Astrophysics Group, University of Warwick, UK
tel +44 2476 523390 fax +44 2476 692016
mobile 07740 291984
* * * * * * * * * * *


Scientists have come to realize that certain complex phenomena in nature
share the common feature that 'extreme events' -  that is,  events on a
scale much larger than the average -  are much more likely to happen than we
would expect from our 'everyday experience' or from traditional theories.
Examples of such phenomena include solar activity, earthquakes, forest
fires, space weather and turbulence. With the aim of understanding how such
phenomena behave, and being able to calculate how likely extreme events are,
world experts in the subject are holding a one-day workshop as part of the
Royal Astronomical Society's monthly meeting in London on 8 December. The
workshop, entitled 'Self Organised Criticality and Turbulence in the Solar
System' will provide a platform for researchers to air the latest results
from theoretical simulations and observations of these kinds of complex

The meeting is being held at the Geological Society Lecture Theatre,
Burlington House, Piccadilly, London W1, from 10.30 a.m. to 3.30 p.m. on
Friday 8 December. The organisers are Professor Sandra C. Chapman (Space and
Astrophysics, University of Warwick), Dr Sean Oughton (University College
London) and Dr Mervyn P. Freeman (British Antarctic Survey, Cambridge).

For more background and information about this subject, or about the
meeting, contact Professor Chapman. (See contact details at the head of this

A programme is on



From Michael Paine <>

Dear Benny,

After reading the excellent paper by Curt Mileikowsky and co. (CCNet 1 Dec
2000) I wondered whether planetary systems could *quickly* exchange rocks,
and therefore microbes. The Mileikowsky paper seems to suggest that it is
extremely unlikely that DNA-based organisms could survive in
space for millions of years (they use 100,000 years *flight time* as a limit
for calculating the quantity of viable organisms exchanged between Earth and
Mars). Assuming this is the case then the current distances to the nearest
stars make survival aboard meteoroids ejected from the Earth
extremely unlikely (comets may be a different matter - but I won't enter
that debate). The other problem is the poor chances of actually encountering
a planetary system after drifting through space for millions of years.

There is, however, a mechanism that might increase the chances of exhange of
rocks between planetary system - THE STARS MIGHT COME TO US. In 1981, Jack
Hills published a paper 'Comet showers and the steady-state infall of comets
from the Oort cloud'. He was looking at a possible cause of comet
bombardments. As part of this work he derived estimates of the mean time
between stars passing within a given distance of our Sun. I don't know if
there have been updates to these estimates but here is a summary of his

Minimum distance between Mean interval
star and Sun (au)       (years)
500au 5 billion
1,000au 1 billion
5,000au 40 million
10,000au 10 million

This suggests that over the lifetime of the Earth about 4 star systems may
have come within 1,000au of the Sun. It would be interesting to work out the
odds of a microbe-bearing Earth rock finding its way into this region of the
solar system (perhaps through encounters with Mars and/or
Jupiter - the estimate is that several hundred kilograms of Earth rocks
reach the surface of Mars each years so a reasonable number must just miss
Mars and receive a slingshot to the outer solar system). Then the odds of it
being *picked up* by a passing star and landing on a suitable planet - all
within, say, 1 million years. No doubt they are extremely poor odds - but it
would just take one successful exchange for panspermia to succeed.

One positive factor in this speculation is that it would take several years
for the star to pass "through" the solar system. During this time there may
be a major bombardment of the Earth by comets disturbed from the Oort cloud.
The number of launches of rocks bearing microbes would therefore increase
during this period (the delay in comets reaching the inner solar system may
defeat this idea). Over to the experts...

Michael Paine


From Andrew Glikson <>

Dear Benny,
Fred Hoyle and Wickramasinghe (CCNet, 4.12.2000) state "We do not wish to
enter into a debate in your columns rebutting critics of panspermia.",
conceivably referring among other to views expressed in CCNet essay
When stating "Not so long ago the Darwin-Wallace theory of evolution was
condemned using precisely such arguments. It is time your correspondents
learnt the lessons of history that facts, not opinions, are all that
ultimately matter", do Hoyle and Wickramasinghe suggest that (1) acceptance
of Darwin's evolutionary theory imply life exists in comets or intergalactic
dust, or (2) cometary and cosmic amino acids are equivalent to microbial
spores and life? or (3) by "facts" are they referring to the
"extraterrestrial" bacterium collected by a weather balloon at 16 km
altitude (CCNet, 28.11.2000) - a level exposed to terrestrial contamination?

As eminent physicists the two gentlemen are without doubt acquainted with
the principle of "falsifyability" - the unique strength of the scientific
method being the inherent and necessary exposure of ideas to critical
examination, as distinct from theological dogma. That the panspermia
suggestion has resulted in a wide debate, therefore, testifies to its
potentially far reaching implications, and is in this sense a compliment to
its authors. Conversely, the day panspermia ceases to be a subject of debate
will be a sad day for the theory. Unless Hoyle and Wickramasinghe claim
their suggestions are now proven and beyond debate, criticism of the theory
ought not to be treated as some sacrilegious heresy by unholy critics.
Andrew Glikson
5 December, 2000
Australian National University
Canberra, ACT 0200


From Jon Richfield <>

Dear Benny,

The Panspermia debate has been heating up so drastically of late that I am
moved to respond to new developments. I had intended ignoring the subject
ever since I finished writing an essay published on CCNet some time ago, but
both published putative discoveries and private email have moved me to
revise that essay. The new version is swankier in format, (RTF, with page
numbering and table of contents and all that Good Stuff that demonstrates
that it must be scientifically cogent) but it also deals with some rather
startling claims and lines of reasoning that I have encountered from
Panspermia enthusiasts.

Then there is some discussion of the implications of Martian and Lunar
fossils, of the plausibility of a continual drizzle of alien genetic
material and its logical irrelevance to terrestrial evolution, of the
tininess of our closed universe and so on.

Honestly, if I thought this subject had any staying power, I would write a
book about it.

Anyway FWIW, to anyone reading the essay: enjoy. Or if you cannot do that,
have fun blasting me. I prefer friendly blasting, but I do not insist on it
and shall cheerfully respond to anything with technical or logical
substance, polite or not. Trollers who fail to pay their way with such
substance however, need not hold their breath waiting for the penny to drop.
For the rest of you, thanks for your attention!



Professor Sir Fred Hoyle and Professor Chandra Wickramasinghe are perfectly
correct that facts are what ultimately matter (in science), but they could
profitably reflect that bare assertions are not what determine facts. It
certainly might be an unprofitable exercise for them to debate
Panspermia, or for that matter "astrobiology" or "bioastronomy" with critics
if those critics were uniformly reliant on sociology or other trivialities
in lieu of substance.

However, it would be strange if every contribution to a forum of this
standard were indeed jejune. To be sure, several items have appeared that I
for one regard as negligible, but then, the moderator goes out of his way to
accommodate a representative range of views and more strength to him, say I.
If the professors are caught short, I could happily oblige them by
assembling a few salient facts that have a long history of distressingly
taking the wind from the sails of panspermic assertions and inferences.

The trouble is probably that Panspermia intrinsically involves biology,
chemistry, information theory and related disciplines that place far tighter
constraints on tenable speculations and conclusions than cosmology does,
which is where the more free-wheeling panspermists find themselves most

A large proportion of assertions in such mundane fields have very broad and
varied implications and therefore lend themselves to both indirect and
direct falsification by controlled observations of tight precision. It is
therefore hazardous to assume that a biological speculation is secure
against critics just because its immediate substance is not falsifiable.
For instance, a self-indulgent speculation concerning the source and
destination of exotic genetic material might encounter embarrassing
challenges from fields such as information theory and epidemiology.

For just such reasons it is a curious anomaly to invoke the history of
"sociological arguments" against Darwinism as an example. Many of the
Panspermia apologists I have debated facts with have been so poorly informed
on Darwinism that though they would hotly have denied it, their claims were
actually anti-Darwinistic!

Darwinism did not prevail because its proponents eschewed sociology; in fact
they employed it as much as anyone. For instance they got prominent persons
to espouse the theory in public debate. This is very much as Professor Sir
Fred Hoyle and Professor Chandra Wickramasinghe are currently doing for
Panspermia, in fact. The Darwinists' success in the long run had rather to
do with their having a good deal more of a coherent structure of facts and
logical implication than anything that Panspermia as she currently is spoke
has any hope of approaching.

Another point is that not all proponents of Darwinism were equally sound.
Many spoke greater rubbish than most of the opposition. Many still do in
fact. It is quite an embarrassment, particularly as some prominent
professors who think they know better and who ought to know better, talk
some of the glibbest tripe. This makes it hard to deal with it at once
courteously and plausibly.

Similarly I am sure that currently some opponents of Panspermia must be
talking embarrassing nonsense and invoking "sociological arguments", but
surely Professor Sir Fred Hoyle and Professor Chandra Wickramasinghe are not
suggesting that such shortcomings are so uniform among the doubters, that
the professors can in good conscience and good sense claim "sociological
arguments" as a valid refutation and blanket justification for ignoring all

All the best,



From Neil Bone <>

The CCNet essay by Palmer and Palmer is interesting in producing numerous
accounts of celestial phenomena circa AD 850. Surely, however, great caution
must be exercised in interpreting these - far from all are necessarily
cometary in nature.  Indeed, a majority seem more likely to
have been naive accounts of auroral displays, this being a time of already
documented high solar activity.

For example, in AD 836  "strange rays of light appeared from east to west
iun the night sky" reads more like a reasonable description of an auroral
arc or band spanning the northern sky, than the tails of a comet (even De

Descriptions from AD 837 of "dragons"  are also consistent with some auroral
forms - twisting bands have been described in some literature as serpents or

The AD 838-839 (and later) accounts of "army of fiery red and other
colours..,. in the sky" also echo a common theme in auroral descriptions
from the time. The fiery red colour (excited oxygen around 400 km altitude)
is common in active aurorae reaching lower latitudes - eg 1991 Nov 8-9, 2000
Apr 6-7 - and has frequently figured in medieval writings about batles in
the sky, swords dripping blood, and so forth. The Scottish astronomical
historian Dr David Gavine has unearthed large numbers of such writings from
this period. Some of his examples are given in my book 'The Aurora:
Sun-Earth Interactions' (Wiley/Praxis, 1996, 2nd Ed).

The AD 841 rings of light are nothing more exotic than routine atmospheric
halos, produced when cirrus cloud passes in front of the Sun - about as far
as one can get from cometary phenomena!

Basically, there's no need to interpret everything seen in the sky in terms
of a catastrophic near-Earth comet.; less exotic - but still interesting -
and more plausible explanations are available for many of the events

Neil Bone

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