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(meteorobs) Excerpts from "CCNet 97/2001 - 4 September 2001"
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From: Benny Peiser <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet 97/2001 - 4 September 2001
Date: Tue, 4 Sep 2001 12:29:17 +0100
CCNet 97/2001 - 4 September 2001
--------------------------------
"We detected [an unusual fireball] in 1997 and reported in 1998 at
the IAU Colloquium in Tatranska Lomnica. The fireball had a retrograde
cometary orbit, but it penetrated much deeper in the atmosphere than any
cometary fireball (such as a Leonid) of comparable velocity of mass.
Moreover, the spectrum was unusual by the absence of normally bright
sodium line. We concluded that we observed a compact body (of mass about 0.2
kg), probably of asteroidal density and non-chondritic composition on
cometary orbit (i=138 deg, q=1.01 AU, a=3.5 AU). At that time, no
asteroid on retrograde orbit was known. This changed in 1999 with
the discovery of 1999 LD31 and 1999 LE31. It is probable that the fireball
we observed is related to the group now known as Damocloids."
--Jiri Borovicka, Ondrejov Observatory, 4 September 2001
(1) LOW SOUNDS DETECT METEOR BLAST
BBC News Online, 3 September 2001
(2) A METEOR'S REMNANTS DRAW A POSSE
The New York Times, 2 September 2001
(3) INUIT, NASA AT ODDS OVER IMPACT CRATER
National Post, 3 September 2001
(4) DAMOCLOIDS
Jiri Borovicka <borovic@asudot cas.cz>
[...]
======================================================================
(1) LOW SOUNDS DETECT METEOR BLAST
>From the BBC News Online, 3 September 2001
http://news.bbc.codot uk/hi/english/sci/tech/newsid_1522000/1522932.stm
By BBC News Online science editor Dr David Whitehouse
One of the first stations of what will be a global "infrasound" listening
network, has detected a meteor that exploded over the Pacific Ocean with the
force of the Hiroshima nuclear blast.
"Infrasound" refers to sound waves that fall below the 20 hertz lower level
of human hearing. The new detectors record signals that are too faint, and
vary too slowly, to be detected by humans.
The global network is designed to monitor clandestine nuclear tests but
scientists say it will have many scientific uses as well.
It will be able to detect previously unsuspected meteor entries into the
atmosphere, volcanic eruptions, and the formation of hurricanes.
Hiroshima blast
One of the first significant signals received by the infrasound array built
by the Scripps Institute of Oceanography at the University of California,
San Diego, was of a meteor that came crashing into the Earth's atmosphere on
23 April.
The first data from the array comes through
Estimated at between 2-3 metres (8 - 10 feet) across, it exploded with a
yield of a few thousand tonnes of TNT, nearly the force of the atomic weapon
that was dropped on Hiroshima.
"If this rock had come into the atmosphere at a slightly different time, it
might have exploded not over the Pacific, but over a large metropolitan
area," said Dr Michael Hedlin of the Scripps Institute.
"With this global listening network we can develop much better statistics on
large meteors and get a better idea of how often these massive objects enter
the atmosphere."
Large explosions send part of their acoustic energy into the audible range,
but those signals dissipate rapidly. But they also emit large amounts of
energy into the infrasonic range in signals that decay slowly across vast
distances.
The 23 April explosion occurred 1,800 km (1,118 miles) away from the Scripps
detector. It was also detected by an infrasound array in Germany, 11,000 km
(6,835 miles) away.
'Unprecedented opportunity'
As well as meteors, infrasonic sound is generated by supersonic aircraft,
tornadoes, earthquakes and volcanoes.
The infrasound detector up close
According to Hedlin, scientists have already discovered that volcanic
eruptions produce strong infrasonic signals, "seismic and infrasound data
taken together give a much fuller account of activity inside the volcano
that might be indicative of an impending, significant eruption."
Scientists are also planning to build a new infrasonic array at Cape Verde
in western Africa, near to a region where hurricanes develop and emit
infrasonic signals.
"There is a lot going on in the atmosphere that we need to know more about.
The infrasound network will offer us an unprecedented opportunity to better
understand these phenomena on a global scale.
"We anticipate that this global network of listening posts that monitors
Earth's fluid exterior shell where we live will someday become as
indispensable as the global seismic network that monitors the Earth's solid
interior for seismic activity."
Copyright 2001, BBC
======================================================================
(2) A METEOR'S REMNANTS DRAW A POSSE
>From The New York Times, 2 September 2001
http://www.nytimes.com/2001/09/02/science/02METE.html
By THE NEW YORK TIMES
ENVER, Sept. 1 - The hunt will soon be on for the remnants of a meteor that
lighted up the night sky last month, dazzling witnesses in several states.
On the night of Aug. 17, away from the city lights of this rapidly growing
region, people - whether they were sitting in a hot tub, taking a break on a
porch swing or gathering around a campfire - stopped and looked to the
stars. Witnesses from as far north as Idaho and as far south as New Mexico
said they saw a brilliant fireball. Some Coloradans heard sonic booms.
Data from an acoustic tracking system at a laboratory in Los Alamos, N.M.,
indicated that the meteor was 40 times brighter than a full moon and might
have weighed a ton as it hit the Earth's atmosphere traveling about 11.25
miles a second.
"As we were sitting around the fire talking, all of a sudden it looked like
the sun had come up," said Kent Hups, 43, a tae kwon do teacher from
Thornton, Colo. Mr. Hups was staying at a guest ranch outside of Gunnison,
Colo., when he saw the meteor with 15 other people. "As it came down, it
sizzled and broke up and then turned red. Like a minute later we started
hearing explosions."
Jack Murphy, geology curator with the Denver Museum of Nature and Science,
said: "This isn't the typical fireball. This is bigger and brighter than
anything we've worked on before."
The unusual trajectory - straight down rather than an arc - and intensity of
the meteor could mean that the remaining meteorite is made of iron instead
of stone, as most are. Mr. Murphy said that any sounds made by the meteor
were probably made as the rock moved through the atmosphere, a journey that
also burned most of its mass.
Mr. Murphy has put hundreds of miles on his car seeking out people like Mr.
Hups. Mr. Murphy has also received hundreds of telephone calls and e-mail
messages. Each interview can provide another clue in narrowing the area to
search for a meteorite, the rock that remains after a meteor falls to the
ground. Mr. Murphy leads a "meteorite posse" of mostly volunteers and plans
to keep gathering data, including witness accounts, compass bearings and
altitude measurements, for at least one more week before conducting a ground
search.
A meteorite is the property of the owner of the land it falls on, and any
meteorite hunters must receive permission from private or government
landowners to remove the space rock. "What we'd like is for the landowners
to invite our team to do a search for them," Mr. Murphy said.
The sooner the meteorite is found the better for scientific research, if for
example, there is water inside it.
"The allure of meteorites, from a scientific standpoint, is that they are
oldest things we can get our hands on," said Matt Morgan, a geologist for
the Colorado Geological Survey. "Rocks on Earth are 3.6 billion years old,
and rocks from space are maybe 4.5 billion years old. It can be a great
sample of the asteroid belt."
Mr. Morgan, the author of "The Handbook of Colorado Meteorites," did not see
the fireball but did research and planned a search in the mountains of
Colorado. "What's really cool for me is being the first one to touch it,"
Mr. Morgan said with a laugh. "It's the poor man's space sample."
Despite the dramatic light show, Mr. Morgan said, the meteorite could be the
size of a baseball or smaller, or it could be broken into thousands of
fragments. And he said that, unlike in the movies, there were no burn marks
to lead researchers down the path to the rock.
Mr. Morgan buys and sells meteorites on the Internet and said that prices
ranged from $1 to $2 a gram to thousands of dollars per gram for lunar or
Martian rocks. "They're more rare than gold," he said.
But for many the biggest thrill was just to see the meteor. "It's a pretty
big event around here," said Patti Powers, owner of the Antlers Rio Grande
Lodge and Riverside Restaurant in Creede, Colo. "The sky just lit up from
horizon to horizon, and then it was like a full moon coming down as it
actually fell."
Mr. Hups said he planned to join the search with Mr. Murphy. "This will make
finding a needle in a haystack look easy," Mr. Hups said. "I figure I can
buy a Powerball ticket or find meteorites, the odds are the same."
Copyright 2001, The New York Times
======================================================================
(3) INUIT, NASA AT ODDS OVER IMPACT CRATER
>From National Post, 3 September 2001
http://www.nationalpost.com/news/national/story.html?f=/stories/20010903/681
689.html
Community 200 km from Mars project seeks compensation from space researchers
Brad Mackay
National Post
NASA'S PLAN TO COLONIZE MARS CRASHES INTO NUNAVUT POLITICS: Left to right,
Tam Czarnik, Eric Tilenius and George James venture out for a "spacewalk" on
the rim of Devon Island's Haughton Crater in August. The crater is a
suitable stand-in for barren Mars thanks to a meteor impact millions of
years ago. This picture was taken by Dr. Pascal Lee, the project's principal
investigator, who added the Mars-like tint.:
Residents of a remote northern community won't allow researchers with the
National Aeronautics and Space Agency's Haughton-Mars Project on to
Inuit-owned land on Devon Island unless an agreement for benefits is
negotiated.
Two weeks ago, representatives of Grise Fiord, a hamlet of 170 people on the
southern coast of Ellesmere Island, visited the site of the NASA-sponsored
project on the rim of the Haughton Crater, the site of a 20-kilometre impact
caused by a meteor collision millions of years ago.
The international group of scientists, engineers and students have been
working on the crater site for three years as part of the Haughton-Mars
Project, which aims to eventually colonize Mars. The barren location was
selected by the research team because of its similarity to the surface of
the Red Planet.
But for the past year, Grise Fiord officials have forbidden anyone
associated with the project to use Inuit-owned lands, which comprise 70% of
the area around the Haughton Crater.
While touring the site recently, the eight-member delegation, which included
the mayor of Grise Fiord, broached the subject of compensation.
FULL ARTICLE at
http://www.nationalpost.com/news/national/story.html?f=/stories/20010903/681689.
html
======================================================================
* LETTERS TO THE MODERATOR *
======================================================================
(4) DAMOCLOIDS
>From Jiri Borovicka <borovic@asudot cas.cz>
Dear Benny,
to add something from my field to the recent discussion on Damocloids, I
would like to mention an unusual fireball we detected in 1997 and reported
in 1998 at the IAU Colloquium in Tatranska Lomnica. The fireball had a
retrograde cometary orbit, but it penetrated much deeper in the atmosphere
than any cometary fireball (such as a Leonid) of comparable velocity of
mass. Moreover, the spectrum was unusual by the absence of normally bright
sodium line. We concluded that we observed a compact body (of mass about 0.2
kg), probably of asteroidal density and non-chondritic composition on
cometary orbit (i=138 deg, q=1.01 AU, a=3.5 AU). At that time, no asteroid
on retrograde orbit was known. This changed in 1999 with the discovery of
1999 LD31 and 1999 LE31. It is probable that the fireball we observed is
related to the group now known as Damocloids. The relatively small semimajor
axis of the fireball is a selection effect - it is more probable to see an
impact of body of smaller orbital period.
What is interesting is the compact nature of the meteoroid. It implies that,
if Damocloids are extinct comets, they may contain quite compact boulders.
Or that Damocloids are not comets at all. I am curious what will show
physical observations of 2001 OG108.
Note that collision of the Earth with a Damocloid can be quite energetic.
The velocity of the fireball we observed was 65 km/s.
Jiri Borovicka
Ondrejov Observatory
Reference
Spurny P., Borovicka J.: Detection of a high density meteoroid on cometary
orbit. In: Evolution and source regions of asteroids and comets. eds: J.
Svoren, E.M. Pittich, H. Rickman. Astron. Inst., Slovak Acad.
Sci.,Tatranska Lomnica, IAU Coll. 173, pp. 163-168 (1999)
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