PLEASE NOTE:
*
CCNet 115/2000 - 9 November 2000
THE DEBATE GOES ON: WHAT ARE THE LESSONS FROM THE SG344
DEBACLE?
----------------------------------------------------------------
"An earthquake expert urged openness about any potential
threat, as
long as the uncertainty of initial observations is clearly
explained. "You can't control the flow of news but you can
be as truthful
as possible up front," said Allan Lindh of the U.S.
Geological Survey. "The
press, public and public officials seem to deal well with
uncertainty, but
they don't deal well with the suggestion you might hold out on
them."
-- ABC News, 7 June 1998
(1) LET'S NOT GET TO UPTIGHT ABOUT MEDIA FLAPS
Mark Sonter <sonter@camtech.net.au>
(2) LET'S NOT CRY 'WOLF' TOO OFTEN
John Nuckols <jrnuckols@home.com>
(3) ON PUBLIC RELATIONS & THE FLEXIBILITY OF IAU GUIDELINES
Jacqueline Mitton <aco01@dial.pipex.com>
(4) LET'S MILITARIZE THE IMPACT RISK ASSESSMENT!
Jon Giorgini <jon_giorgini@hotmail.com>
(5) 2000 SG344: LUNAR IMPACT EJECTA?
Roy Anthony Tucker <gpobs@azstarnet.com
(6) ASTEROID 2000 UG11
SpaceWeather.com <express@spacescience.com>
(7) OBJECTIONS TO THE USE OF NUCLEAR POWER & OTHER
MISCONCEPTIONS
Syuzo Isobe <isobesz@cc.nao.ac.jp>
(8) QUESTIONS ON ASTEROID 2000 UV13 DISCOVERED BY THE JAPAN
SPACEGUARD
ASSOCIATION
From David J. Asher & Syuzo Isobe
(9) WALTER HASS' 1941 TLP in GASSENDI - ANY CRATER FOUND?
Larry Klaes <lklaes@BBN.COM>
(10) JUST AS YOU THOUGHT YOU COULD BREATHE A SIGH OF RELIEF, THIS
COMES ALONG:
"ASTEROID ON COLLISION WITH
EARTH"
Sky News, 9 November 2000
(11) AND FINALLY - SOMETHING NEW FOR DOOM MERCHANTS:
"NASA MISSION COULD LEAD TO INTERPLANETARY PLAGUE"
Entire species may be wiped out by NASA plans to bring Mars soil
or rocks to Earth.
The Press Association, 9 November 2000
====================
(1) "LET'S NOT GET TO UPTIGHT ABOUT MEDIA FLAPS"
From Mark Sonter <sonter@camtech.net.au>
Dear Benny,
Firstly, I greatly appreciate CCNet and the information that it
makes
available from a wide range of sources: to set out to collect,
and maintain
coverage of this range of material would be otherwise impossible.
I think
you are doing a great job.
Secondly, regarding the Global Warming debate: it clearly is not
as 'cut and
dried' as the environmentalist orthodoxy would have one believe.
And I for
one certianly appreciate being kept up to date in this area. But
yesterday's
suggestion of a 'weekly special' on the topic, and maintaining
the general
daily focus on asteroid impact discussions, is a reasonable
structure.
Thirdly, I had hoped to catch up with you during my recent visit
to the UK
but was unsuccessful, and I regret that.
Fourthly, I think you are getting too uptight about "media
flaps" and
less-than-perfect information review mechanisms re 2000 SG344;
the facts
are,
(i) the media will get the info, anyway, (or at least I hope they
will, 'cos
that's their job, innit??) and will tend to get it 'only half
right' much of
the time, or (sometimes) will blatantly beat up a sensationalist
story; but
that's life, and many readers -and all politicians- will
recognise that;
(ii) you must avoid at all costs any suggestion that information
is being
censored or held back; the idea of stifling the release of
information
should be regarded as anathema, and the idea of delaying its
release fills
me with trepidation. It would be far better to release incomplete
information with a rider that some precovery image may change it
all
tomorrow, AND ACCEPT THAT EMBARRASSMENT,
than to construct some well-meaning self-censoring mechanism
that the government can then take over, to use for issuing
soothing releases
that can turn out to be ill-judged, as per the recent revelations
regarding
the UK government's handling of Mad Cow Disease and it's
capability of
jumping the species barrier.....
(iii) these scares actually have a positive effect, inasmuch as
they will
gradually prod the governments of the world into thinking
seriously about
this stuff. I don't think we should worry about the 'cry wolf'
syndrome,
provided we are not ourselves 'beating up' an exaggerated
story. I do think
it is totally reasonable for articles about the realistic
possibilities of
asteroid / comet impact to appear in the popular media, even if
they are not
written as you or I might prefer.... There's nothing like these
'out in the
open' will-it-hit-us-won't-it-hit-us debates to show science in
action, with
all its warts. Give the populace credit for some nouce, and let
them see the
unfolding and development of the information.....
Anyway, keep up the good work, and congratulations on the recent
release of
the UK NEO Task Force Report, which I think will do a lot to
remove finally
the 'giggle factor' problem.
Best Regards,
Mark Sonter
MODERATOR'S NOTE: Mark, I fully share your stoic view, in
particular with
regards to some of the media that will always exaggerate
NEO-related
information regardless of *what* is being said. But let me stress
again: I
am *not* suggesting that impact risk calculations (regardless how
high they
score on the Torino Scale) should be censored or held back. I
thought I have
made pretty clear that I advocate the opposite! According to the
current IAU
guidelines, there is a very counter-productive 72 hours secrecy
period in
place during which impact probability calculations for
newly discovered
objects that score 1 or higher on the Torino Scale are checked.
The problem
is that this three day secrecy prevents many observers around the
world to
be informed adequately and in time. Consequently, they cannot
search their
files or make crucial follow-up observations. The knock-on effect
of this is
that the IAU team, working on the calculations within this
limited time
frame, may not receive additional data that might eliminate the
impact risk
or significantly reduce its probability. This is what happened
with the
SG344 scare.
In short, I feel that at least three things need to be changed in
order to
make the IAU guidelines more effective:
1.) Whenever a newly discovered NEO is found to have a
significant impact
probability (i.e. after a review and confirmation by another team
of orbit
calculators), this information should be posted on the NEODyS
Risk Page and
on a MPC website without delay. Crucially, additional information
needs to
be provided on the same website that emphasises that further
observations or
pre-covery data will, in all likelihood, eliminate this risk.
2.) The 72 hours secrecy period should be scrapped together with
the
requirement that after that time an IAU announcement has to
follow if the
impact probability is still significant. Instead, a new waiting
period
should be established that is related to the period during which
additional
observations can be made that could eliminate the threat. If,
after this
time, no further observations are possible for a prolonged
period, and if
the impact probability is still significant, the IAU WGNEO should
issue a
public statement.
3.) Given the variety of NEOs and the fluctuation of impact
probability
calculations (i.e. size of the object, time of close approaches,
time of
impact probability, etc.) the IAU should adopt a
case-by-case approach to
the problem that leaves enough flexibility for an adequate
response.
Let me conclude with a timely reminder of what an expert in
natural disaster
management had to say in the aftermath of the 1997 XF11 asteroid
scare: "An
earthquake expert urged openness about any potential threat, as
long as the
uncertainty of initial observations is clearly explained.
"You can't control
the flow of news but you can be as truthful as possible up
front," said
Allan Lindh of the U.S. Geological Survey. "The press,
public and public
officials seem to deal well with uncertainty, but they don't deal
well with
the suggestion you might hold out on them."
http://abcnews.go.com/sections/science/DailyNews/asteroidconference980607.html
Does that sound convincing, Mark?
================
(2) "LET'S NOT CRY 'WOLF' TOO OFTEN"
From John Nuckols <jrnuckols@home.com>
Dear Benny,
I commend your response to Bev. (IMPACT RISK DATA SHOULD NOT BE
WITHHELD).
The problem seems to be the current 72 hour rule requiring an IAU
notification to the public in the event of an early Torino 1 or
higher
indication, as you noted in your response to Bev. This is not
nearly enough
time, and consequently may often lead to embarrassment such as
recently
occurred in the case of 2000 SG344. Embarrassment, of course, is
the least
of our concerns. The long term damage could be
worse. The public will begin to laugh at and ignore the very real
threat
which the world faces every day from NEAs.
Unless we are confronted with a sudden uncontrovertible danger
from an NEA,
it would seem to be so much better for the scientific community
to examine
each discovery of a possible danger for a reasonable period, say
6 months,
before any public announcement were made. This would eliminate
most of the
perceived threats, as well as much embarrassment. Let's not cry
"wolf" too
often.
John Nuckols
================
(3) ON PUBLIC RELATIONS & THE FLEXIBILITY OF IAU GUIDELINES
From Jacqueline Mitton <aco01@dial.pipex.com>
Dear Benny
It is good that the principle has been established of a proper
procedure for
informing the media and the public of discoveries of potentially
Earth
threatening objects, but it is now clear that the handling
of the SG344
affair still did not achieve the goal of clear factual
communication.
Would it not be a good idea if the Review Team deciding whether
and when to
issue a statement about potentially Earth threatening objects,
and the IAU,
were to involve a few trusted individuals who have substantial
expertise in
media relations and/or who are working in the science media?
No-one can
totally predict how the media will react to any particular event,
and it is
even more difficult trying to control what they do. But long
experience
certainly helps. The precise wording of press and public
statements and
subtleties of emphasis can make all the difference to how they
are
interpreted. Timing is also important. The SG344 story evolved
rapidly over
a weekend which, with hindsight, was predictable when the
announcement was
made on a Friday. This meant that it was difficult for the media
to get hold
of experts and the all-important 'retraction' came out on a
Sunday, the
worst day of all from a practical point of view. It is certainly
one of the
reasons it has proved difficult to put the record straight in
many sectors
of the media.
The guidelines under which the Review Team are operating should
perhaps be
more flexible, and I would suggest that some PR advice would not
come amiss
for handling such sensitive and potentially sensational
announcements.
Jacqueline Mitton
Royal Astronomical Society Press Officer
jmitton@dial.pipex.com
phone (+44) (0)1223 564914 fax (+44) (0)1223 572892
================
(4) "LET'S MILITARIZE THE IMPACT RISK ASSESSMENT!"
From Jon Giorgini <jon_giorgini@hotmail.com>
Dr. Peiser:
Regarding 2000 SG344 ...
A) Archival survey data needs to be involved and accessible.
http://skys.gsfc.nasa.gov/skymorph/skymorph.html
is an appropriate tool, but
Catalina and LONEOS, for example, are not included though
participation has
been advocated previously.
B) Public announcements in a fixed-time span are unimportant
compared to
correct statements.
C) "Impact" is an intrinsically biased/inflammatory
word and not actually
what the probability calculations refer to. The calculations
address
trajectory intersection. Claims of impact depend on object
composition,
fracture (in this case, rivet?) status, and a host of assumptions
used in
place of actual facts, many of which can't be known.
This science is coming out of an academic setting in which
best-guess
speculations can be floated for later academic refutation, and
occasionally
even actual data. The habit is so ingrained, the
distinction between what one knows and what one thinks one knows
can
sometimes be over-looked. If one is going to deal in the
real world and
presume to affect public life, speculation beyond actual data
in-hand is
inadequate.
D) 1/500 are long odds for people's attention to be drawn to.
Weather
forecasts don't even bother talking about a 10% chance of rain
due to the
repetitive failure involved. Need higher-standards of
probability and
time-horizon before public announcement.
E) Obtaining media attention does not justify incomplete analysis
and
unsupportable speculation. Ends justifying the means leads to
unethical
behavior, where people think they can do anything they want
because they
think they are saving the world. Enthusiastic support of the
release of
speculation, endorsed by people educated in journalism not
science, is based
on journalism, not science.
F) The insistent call for "open process" is ludicrous,
with motivations that
need to be carefully examined. The Air Force has remained on
continuous
alert for 40+ years searching for missile
launches. There is a command hierarchy. Work is anonymized to
reduce
ego-based, self-appointed, self-aggrandizing saviors. Imagine if
it was
handled by e-mail, with people posting their results on
web-sites. LINEAR
has already demonstrated the Air Force's ability to mount an
overwhelmingly
superior search effort. Let's not treat it as a joke; recognize
the reality
of the risk by militarizing it. Let conspiracy buffs make a
fortune writing
all the dumb books they want.
It may not be as exciting for some not be able to save the world
by
e-mailing back of envelope calculations about how many
Hiroshima's the
latest one packs, but it may be a test of how pure one's motives
are. Is
this a serious issue or a fun way to feel important without
actual
responsibility?
Personal thoughts only,
Jon Giorgini
MODERATOR'S NOTE: Jon, I agree with some of what you're saying.
However, I
don't think it would be wise or indeed necessary to
"militarise" the
handling of NEO impact risk assessments. After all, there is a
radical
difference between i) the (mis)handling of classified military
information
that can easily have direct and dire consequences, and ii) the
(mis)handling
of hypothetical impact risk calculations that only lead to the
occasional PR
fiasco which, if I dare say, almost appear 'normal' in view of
yesterday's
media boo-boos, U-turns and political retractions concerning the
U.S.
presidential elections.
=================
(5) 2000 SG344: LUNAR IMPACT EJECTA?
From Roy Anthony Tucker <gpobs@azstarnet.com
[as posted on the MPML mailing list]
Ladies and Gentlemen of the list,
I'm very intrigued by the possibility that 2000 SG344 could be
lunar impact
ejecta since the hypothesis that it could be an Apollo S-IVB is
only
marginally plausible and it is difficult to get a Main Belt
object into to
such an orbit. I read the article by Tancredi ("An asteroid
in
an Earth-like orbit", 1998) and was impressed by how well
his proposed lunar
ejection model matched the orbital characteristics of 1991 VG and
2000
SG344. The question then is how to launch such large fragments
off the moon.
It would require a large impact, of course, and Giordano Bruno
is one of the freshest-looking craters on the moon. An impact in
1178 is not
required but whatever event ejected these objects should have
occurred
within the last million years or so.
Examining the total mass of US Antarctic meteorite finds of 1,902
kilograms
we find 11 lunar-origin meteorites with a total mass of about 1.7
kilograms.
We might then wildly estimate that 0.1% (one part in a thousand)
of the
approximately 36500 tons of meteoric matter that falls to the
earth each
year is lunar in origin on the average or about 3.5x10^7
grams/year.
Assuming a density of 2.5 grams/cm^3, this is the equivalent of
about
1.4x10^7 cm^3 or 1.4x10^-8 km^3 per year.
Let's make some unbridled speculations about these numbers just
for fun.
1991 VG is about 10 meters in size or about 10^-6 km^3, the
equivalent of
about 71 years of lunar-origin meteoric flux. A ten-meter object
may be
expected to encounter the earth about ten times per year.
Simplistically
ignoring size populations of hypothetical lunar ejecta,
if we assert that one out of every 1000 ten-meter sized objects
the earth
encounters is lunar in origin, then we would expect one such
object per
hundred years. According to Tancredi, the terrestrial impact
frequency of
1991 VG is about 5x10^-6 per year, or about once in 200,000
years. Do we
expect a population of about 2,000 1991 VGs?
2000 SG344, if not space junk, is about 50 meters in size or
1.25x10^-5
km^3. This is the equivalent of about 9,000 years of lunar
meteoric flux.
The earth encounters 50-meter objects about once each 100 years
so we might
expect a lunar-origin object of this size about once
in a 100,000 years.
We might also speculate that a search program might find one
lunar-origin
object for every 1,000 NEOs it finds. SpaceWatch found 1991 VG
out of its
total present catch of 200 NEOs.
These numbers don't seem to be implausible. I'm inclined to think
Dave
Tholen may have found a big moon rock. It's intriguing to
speculate where on
the moon such a large ejecta block might have originated.
I'm hoping it's an S-IVB. I'd love to see the weary traveller in
the
Smithsonian some day.
Best regards,
- Roy
==================
(6) ASTEROID 2000 UG11
From SpaceWeather.com <express@spacescience.com>
Space Weather News for Nov. 9, 2000
http://www.spaceweather.com
FAST MOVING ASTEROID: On Nov. 7, 2000, a 250-meter wide asteroid
named 2000
UG11 zipped past our planet just 6.1 times farther away than the
Moon. A
series of movies shows how the apparent speed of the asteroid
rapidly
increased in the early days of November and then peaked at 29
degrees per
day as the space rock made its closest approach to Earth. Amateur
astronomers with 8 inch or larger telescopes can still spot 2000
UG11 for
themselves as it slowly fades this week. [ephemeris for observers
at
http://www.spaceweather.com]
=================
(7) OBJECTIONS TO THE USE OF NUCLEAR POWER & OTHER
MISCONCEPTIONS
From Syuzo Isobe <isobesz@cc.nao.ac.jp>
Nat. Astron. Obs. and Japan Spaceguard
Association
In relation to my comments on objections to the use of nuclear
power in
CCNet last year and on September 29, 2000, I saw several mails
debating this
specific topic. There is also debate on some comments by David
Morrison that
appeared under the headings Misconception No.1 and 2 on October
6, 2000.
Since Morrison cited very important issues on the current
spaceguard
strategy, I will bring the two matters of debate together here.
In Morrison's Misconception No.1 it is clearly said that "We
are
inventorying the population to guard against future impacts. This
is not a
last minute warning system". When NASA's Morrison report was
published in
January 1992, I found this idea in it and I thought and am still
thinking
that the astronomical community can contribute much to the global
human
environmental problem.
Assuming that observers detect an NEA on a collision course, with
a
collision to the earth within a few years, our mitigation options
are
limited. Probably, the only way is to use many nuclear bombs as
illustrated
in the movie "Deep Impact". However, people, who
propose using a nuclear
bomb for mitigation, propose mitigation methods for cases with a
warning
time less than 1 year, or 1 month, or 1 day. Someone may propose
a nuclear
shield system which is an extremely expensive method and has a
high
possibility of not being used within 1,000 years or million
years.
If we have long enough warning time for an asteroid collision,
say longer
than 20 years, we have enough time to prepare for its mitigation.
Once we
detect an PHA and determine its orbit, we can estimate whether it
will hit
the earth within 100 years, and in most cases it will not hit
within this
short period, because the estimated collision probability of an
asteroid
with a diameter larger than 1 km is of the order of once every
hundreds of
thousands of years. Therefore, I am quite certain that the aim we
should
pursue is to detect all the PHA and determine their exact orbits.
Two facts
are relevant here, that collision of an asteroid with a diameter
larger than
1 km has the potential to create a global catastrophe, and that
current
detection telescopes available have apertures around 1 m which is
thought to
detect all of them within a certain period.
As Morrison pointed out, it is very important to have larger
total
cumulative sky coverage to achieve the above aim. Assuming that
there are
many telescopes covering all the celestial sphere at any time it
is certain
that all the PHA with a diameter larger than 1 km can be detected
within a
certain period, say less than 10 years. Therefore, Morrison wrote
"The most
important metric here is not geographic location but total
cumulative sky
coverage". This is true.
However, for ground-based observations we have a weather problem
and also a
limited sky coverage problem. One certainly cannot observe the
celestial sky
area around the South pole from observatories located in the
northern
hemisphere. Any asteroid comes to the northern hemisphere during
its orbital
motion, but of course, the closest approaches of some specific
PHAs to the
earth happen only in the southern hemisphere, although those PHAs
come up to
the northern hemisphere at distances observable by 1 m
telescopes. If you
are keen on detecting a PHA with short warning time, this
certainly remains
a problem. As Morrison stated, the Spaceguard project is to guard
against
future impacts, and therefore the geographic distribution of
spaceguard
telescopes is not inevitably a necessary condition. On the other
hand, the
weather problem is very severe. Currently, most spaceguard
telescopes are
only in one region, the south part of the USA. Therefore there
are several
tens of nights per year when all those sites are cloudy. In this
context,
spaceguard telescopes should be scattered geographically, but
without the
necessity to be in the southern hemisphere. Certainly, however,
since there
are several good sites in the southern hemisphere such as in
Chile, one can
choose those sites.
In the above context, I have the same opinion as Morrison.
However, I have a
different idea regarding his Misconception No. 3 on observations
from space.
If people are concerned with an impact of a PHA with a diameter
much smaller
than 1 km, it becomes far more difficult to detect all of them by
ground
based telescopes. Space-based telescopes are much more
costly, but if most
of the world's people are sufficiently concerned about a local
catastrophe
even if they had to pay a lot, observations from space become
very
important.
Now, I hope you start to understand why I object to using nuclear
power for
mitigation of PHA. The Spaceguard project is targeted to guard
against
future impacts but not near future. Since we have enough time to
develop an
effective method to mitigate PHAs, it is not inevitably necessary
to use
nuclear power to mitigate it, although nuclear bombs are the most
effective
tools at this moment. Presently, there are big discussions either
within the
UN or on other occasions to reduce numbers of nuclear bombs held
in some
countries, and people in most countries in the would support now
throwing
out all nuclear bombs from our world, because they are
potentially hazardous
weapons. There is a certain possibility of using a nuclear bomb
for whatever
reason if they are kept. One can argue for holding a nuclear bomb
in order
to mitigate a PHA, but this makes the possibility of another
hazard remain.
Here, I repeat that it is much more dangerous to keep nuclear
bombs for PHA
mitigation, than a PHA collision itself.
As I wrote, nothing will happen without detecting PHA. Therefore,
let's
always recall the original idea of the spaceguard project
comprehensively
written up in the Morrison report in 1992. Most of the
discussions appearing
since then are heavily weighted towards the PHA problem with
short warning
time. This should not be the real situation.
Finally, I would like to say that since the Torino Scale is
dealing with all
the cases with short to long warning times without distinguishing
them, it
does not fit the Spaceguard project.
Syuzo Isobe
=============
(8) QUESTIONS ON ASTEROID 2000 UV13 DISCOVERED BY THE JAPAN
SPACEGUARD
ASSOCIATION
From Syuzo Isobe & David Asher <isobesz@cc.nao.ac.jp>
David J. Asher (a liaison of the Armargh Observatory and the
Japan
Spaceguard Association)
Syuzo Isobe (National Astronomical Observatory and the Japan
Spaceguard
Association)
Following Duncan Steel's interesting comments in CCNet 111/2000 -
31 October
2000, the question arises as to whether it is surprising that
such a large
(perhaps 10 km) Earth crosser as 2000 UV13 was not discovered
earlier than
last month, when it was found by the Bisei Spaceguard Center.
The orbital period will soon be known well enough for its
visibility at
specific past apparitions to be determined. At present, the
uncertainty in
the period allows a wide range of sky plane positions at previous
returns;
so comments necessarily relate to the range of typical
observability
circumstances that can occur at various returns, rather than
those at a
particular, known return.
Should it have been discovered? Firstly, it would have had to
pass through
the field of a powerful enough telescope. Secondly, it would have
had to be
noticed, measured and followed up.
If a large fraction of the night sky is surveyed to some limiting
magnitude
with sufficient regularity, then objects are followed up
automatically,
except for the few that fade most rapidly. But despite recent
huge increases
in sky coverage, there is still a great need for immediate,
targeted follow
up of new objects (hence the Minor Planet Center's NEO
Confirmation Page).
That is, for many NEOs, it is still the case that if one
discovery chance is
missed, it may be a long time before it next happens to turn up
in a survey
image. And up until the very recent past, this was the case for
virtually
all NEOs.
2000 UV13 has three oppositions about every four years. Of these,
two are
generally when it is in the outer part of its orbit, and although
it is
large for an NEO, it doesn't stand out in the main belt, being
typically mag
18 or 19 at opposition and not with a motion that would
immediately draw
attention to it as an object that had to be followed up, even if
it appeared
as a moving object in an image. (It is large enough that it may
well be
precovered in such an image, of course.) Even if
occasionally at these
oppositions it is moderately far from the ecliptic (30 degrees),
the initial
motion still admits orbit solutions of Hungaria class asteroids
and so it
would not obviously be an NEO.
Usually there is one opposition, the brightest of the three and
different in
character from the others, occurring during the asteroid's return
to the
inner part of its orbit. In contrast to the other
oppositions which are,
observationally, similar to main belt oppositions, here the peak
brightness
may not even be attained near opposition. The observability
circumstances
are different each time, unless the orbit were to have a period
almost
exactly four years, when the relative configuration of asteroid
and Earth
would repeat. Quite a bright magnitude, e.g., 14, 15, 16,
is usually
attained, but this in itself does not guarantee the object would
have been
found. Sometimes the brightest interval coincides with 2000
UV13 having a
small solar elongation, sometimes it is at a very high ecliptic
latitude
north or south (which some surveys are biased against), and
sometimes it
stays near the galactic plane at times that might otherwise offer
the best
discovery chances.
Similar comments would apply to most NEOs, and essentially make a
point that
various people have made, that unless you have virtually
unlimited telescope
capabilities, the laws of celestial mechanics and elliptical
motion do
necessarily mean it takes time to attain near completeness in NEA
discovery
down to some size (value of H). It seems perfectly believable
that an H=13.5
Earth crosser escaped discovery till now, and that there are
other sizable
NEAs, with particular orbit sizes/shapes/orientations that have
also done
so. Let us conclude optimistically by saying that after some
years, the
current great efforts being made in both survey and follow up
should allow
changes in this situation, at least quantitatively.
David J. Asher
Syuzo Isobe
==============
(9) WALTER HASS' 1941 TLP in GASSENDI - ANY CRATER FOUND?
From Larry Klaes <lklaes@BBN.COM>
If you get a Sunday newspaper that carries Parade magazine, the
November 5,
2000 edition has an article on the formation of Luna by David H.
Levy.
In the article Levy mentions the TLP observation by Walter Haas
on July 10,
1941 of a moving luminous object in the crater Gassendi. Levy
speculates
that it was a meteorite striking Luna that Haas witnessed, just
as some
Leonids did in 1999 and may do so again this month.
http://www.mufor.org/tlp/1940.html
My question is: Has anyone checked pre-1941 lunar photographs and
maps of
Gassendi to see if a crater did indeed appear after Haas'
sighting? How
about other similar TLP events?
Larry
===============
(10) JUST AS YOU THOUGHT YOU COULD BREATHE A SIGH OF
RELIEF, THIS COMES ALONG:
"ASTEROID ON COLLISION WITH
EARTH"
From (today's!) Sky News, 9 November 2000
http://www.sky.com/news/technology/story4.htm
Astronomers have issued their strongest-ever warning that an
asteroid could
hit earth, causing a force 100 times greater than the Hiroshima
bomb.....
============
(11) AND FINALLY - SOMETHING NEW FOR DOOM MERCHANTS:
"NASA MISSION COULD LEAD TO INTERPLANETARY PLAGUE"
Entire species may be wiped out by NASA plans to bring Mars soil
or rocks to Earth.
From The Press Association, 9 November 2000
http://www.ananova.com/news/story/sm_110317.html?nav_src=newsIndexHeadline
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