PLEASE NOTE:
*
CCNet, 33/2000 - 15 March 2000
------------------------------
QUOTE OF THE DAY
"The NASA satellite conducting the
first-ever close-up study of an
asteroid will be renamed to honor Dr.
Eugene M. Shoemaker, a
legendary geologist who influenced
decades of research on the role
of asteroids and comets in shaping the
planets. The Near Earth
Asteroid Rendezvous (NEAR) spacecraft,
currently orbiting asteroid
433 Eros more than 145 million miles
from Earth, will now be known
as NEAR Shoemaker."
-- NASA, press
release 14 March 2000
(1) NEAR SHOEMAKER: NASA RENAMES NEAR SPACECRAFT IN HONOUR OF
GENE SHOEMAKER
NASANews@hq.nasa.gov
(2) GLIMPSES INTO EROS' SHADOWS
Ron Baalke <baalke@jpl.nasa.gov>
(3) HOLES IN SUN'S SURFACE EFFECT EARTH'S CLIMATE
Andrew Yee <ayee@nova.astro.utoronto.ca>
(4) A REVIEW OF COMET AND ASTEROID STATISTICS
T. Gehrels, UNIVERSITY OF ARIZONA
(5) ANGULAR MOMENTUM TRANSFER IN OBLIQUE IMPACTS
M. Yanagisawa*) & S. Hasegawa, UNIVERSITY
OF ELECTROCOMMUNICATION
(6) CLARIFICATION
Alan W. Harris <awharris@lithos.jpl.nasa.gov>
(7) A QUICK NOTE ON IMPACT EVENT RATES
Ed Grondine <epgrondine@hotmail.com>
(8) FASTEST SPINNING ASTEROID?
Charles F. Peterson <cfp@mcn.org>
(9) DRAGONS IN THE SKY
Neil Bone <bafb4@central.susx.ac.uk>
(10) THE VIOLENT HABITAT OF EARLY TERRESTRIAL LIFE
Stephen Ashworth <sa@astronist.demon.co.uk>
=========
(1) NEAR SHOEMAKER: NASA RENAMES NEAR SPACECRAFT IN HONOUR OF
GENE SHOEMAKER
From NASANews@hq.nasa.gov
Donald Savage
Headquarters, Washington,
DC
March 14, 2000
(Phone: 202/358-1547)
Mike Buckley
Johns Hopkins University Applied Physics Laboratory, Laurel, MD
(Phone: 240/ 228-7536)
RELEASE: 00-38
NASA RENAMES NEAR SPACECRAFT FOR
PLANETARY SCIENCE PIONEER GENE SHOEMAKER
The NASA satellite conducting the first-ever close-up study of an
asteroid will be renamed to honor Dr. Eugene M. Shoemaker, a
legendary
geologist who influenced decades of research on the role of
asteroids
and comets in shaping the planets. The Near Earth Asteroid
Rendezvous
(NEAR) spacecraft, currently orbiting asteroid 433 Eros more than
145
million miles from Earth, will now be known as NEAR Shoemaker.
"Gene Shoemaker was an inspirational, charismatic pioneer in
the field
of interplanetary science," said Dr. Carl B. Pilcher,
Director of Solar
System Exploration at NASA Headquarters, Washington, DC. Pilcher
announced the new name today during the Lunar and Planetary
Science
Conference in Houston. "It is a fitting tribute that we
place his name
on the spacecraft whose mission will expand on all he taught us
about
asteroids, comets and the origins of our solar system. "
Shoemaker died in a 1997 car accident in the Australian outback
while
on an annual study of asteroid impact craters. With his wife and
research partner, Carolyn, Shoemaker was part of the leading
comet
discovery team of the past century, perhaps most famous for
finding the
comet (Shoemaker-Levy 9) that broke up and collided with Jupiter
in
1994.
He was an expert on craters and the impacts that caused them.
Shoemaker's work on the nature and origin of Meteor Crater in
Arizona
in the 1960s laid the foundation for research on craters
throughout the
solar system. He also established the lunar geological time scale
that
allowed researchers to date the features on the moon's surface.
Though he never realized his dream of tapping a rock hammer on
the
moon, Shoemaker taught Apollo astronauts about craters and lunar
geology before they left Earth. Last year, when NASA's Lunar
Prospector
spacecraft crashed on the Moon in an experiment at the end of its
mission, a small vial of Shoemaker's ashes, carried aboard the
spacecraft, was scattered on the lunar surface.
Shoemaker was a key member of the 1985 working group that first
studied
the NEAR mission, defining its science objectives and designing a
conceptual payload. Many of the group's recommended instruments
were
included in the actual spacecraft, which only a month into its
yearlong
orbit of Eros is already returning fascinating data on the
asteroid's
surface and geology.
The first in NASA's Discovery Program of low-cost planetary
missions,
NEAR launched from Cape Canaveral Air Station, FL, on Feb. 17,
1996.
After a four-year journey that included flybys of Earth (Jan.
1998) and
asteroids Mathilde (June 1997) and Eros (Dec. 1998), NEAR began
orbiting Eros on Feb. 14, 2000. The car-sized spacecraft will
observe
the asteroid from various distances -- coming within several
miles of
the surface -- before the mission ends in February 2001. The
Johns
Hopkins University Applied Physics Laboratory in Laurel, MD,
designed
and built the NEAR spacecraft and manages the mission for NASA's
Office
of Space Science.
EDITORS NOTE: Images and information on the NEAR mission are
available at: http://near.jhuapl.edu
Information on Eugene Shoemaker is available at:
http://wwwflag.wr.usgs.gov/USGSFlag/Space/Shoemaker/GeneObit.html
==================
(2) GLIMPSES INTO EROS' SHADOWS
From Ron Baalke <baalke@jpl.nasa.gov>
NEAR image of the day for 2000 Mar 14
http://near.jhuapl.edu/iod/20000314/index.html
Glimpses into Eros' shadows
This image mosaic, showing Eros' saddle and a shadowed feature to
its
left, was taken from a distance of 204 km (127 miles). In this
picture
features as small as 20 meters (65 feet) are visible. This is the
best
view to date of this area. The sun is coming from the northeast
illuminating a shadowed feature that consists of three large
craters
situated adjacent to each other. The two largest are each about
4-5 km
(2-3 miles) across. Because the sun is very low with respect to
these
craters, even small topographic features cast long shadows,
making them
easier to see. As a result, several boulders can be
distinguished,
ranging from about 50 to 100 meters in diameter, on the crater
walls.
The saddle, on the right of the mosaic, is relatively smooth,
with
few impact craters, and has several grooves running across it. At
the
top of the saddle are several curved grooves that are brighter
than the
surrounding surface. Unusual brightness patterns are also visible
in
the crater at the top left of the mosaic. The walls of the crater
appear to be more reflective and its floor less reflective than
nearby
parts of the asteroid.
--------------------------------------------------------
Built and managed by The Johns Hopkins University Applied Physics
Laboratory, Laurel, Maryland, NEAR was the first spacecraft
launched in
NASA's Discovery Program of low-cost, small-scale planetary
missions.
See the NEAR web page at http://near.jhuapl.edu
for more details.
===================
(3) HOLES IN SUN'S SURFACE EFFECT EARTH'S CLIMATE
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Long Island University
Contact:
Michele Forsten or Alka Gupta
718/488-1015
michele.forsten@liu.edu
Holes in Sun's Surface Affect Earth's Climate
Brooklyn, NY -- An unusual interdisciplinary study by astronomers
and
climatologists has found a striking correlation between holes in
the
outermost layer of the sun -- or the corona -- and the globally
averaged temperature of the Earth, suggesting that the Earth's
atmospheric temperature may be strongly linked to solar magnetism
changes over months or years.
In a paper that appears in the February 28 issue of the journal
New
Astronomy, climatologist Eric Posmentier of Long Island
University's
Brooklyn Campus, solar physicists Willie Soon and Sallie Baliunas
of
the Harvard-Smithsonian Center for Astrophysics and physicist
Pius
Okeke of the University of Nigeria chart temperature anomalies
seen in
the Earth's lower troposphere (i.e., the region of atmosphere in
which
we live) using Microwave Sounding Unit (MSU) radiometers aboard
weather
satellites.
The scientists compared the Earth's temperature with the size of
coronal holes reported on the Sun during a two-decade period,
starting
in January 1979 and ending April 1998. Results show a clear drop
in
terrestrial atmospheric temperature after the Sun's magnetic
field
activity is most intense. At this point, there is a dropping off
of
magnetic activity and an enlargement of the coronal holes.
"This is the
first time anyone has combined these modern, reliable data sets
to link
solar activity and climate, and to cite several alternative
mechanisms
that might explain this link," Posmentier explained.
Coronal holes are, literally, gaps in the Sun's outer atmosphere
through which the stream of hot, supersonic particles known as
the
solar wind pours out into space to engulf the entire planetary
system.
At Earth, this hot bath of charged particles produces the aurorae
(i.e., the aurora borealis), interferes with electrical and radio
transmissions, and may threaten passengers aboard high-flying
airliners
or astronauts aboard unshielded spacecraft. The solar wind has
also
been long suspected as a possible indirect contributor to
terrestrial
climate change.
Posmentier and colleagues think that the connection between the
solar
wind and climate may be more direct, suggesting that the charged
particles hitting the Earth's atmosphere may affect the
properties of
terrestrial water clouds, particularly the percentage of those
clouds
covering the Earth. In turn, significant changes in the cloud
cover
influence the temperature of the lower troposphere, with
temperatures
falling with increased cloud cover. Another possibility is that
the
charged particles change ozone chemistry in the upper atmosphere,
in
turn affecting the dynamics of the climate.
The scientists note, however, that the charged particles hitting
the
Earth could come from either the Sun, or from galactic cosmic
rays that
are modulated by the solar wind. Or, from a combination of both
sources. Regardless, the percentage of the Sun's surface covered
by
coronal holes seems to be a fairly accurate indicator of
temperature in
the Earth's troposphere over months or years.
The correlation comes with some caveats. As Posmentier and
colleagues
note, other major climate factors are also at work concurrently,
thus
complicating attempts to correlate Sun-Earth phenomena. Most
notable in
the past two decades have been the warming effects of the 1997-98
El
Nino and the general cooling that followed the eruption of Mount
Pinatubo in 1991.
According to Posmentier, their results do not rule out the
possible
climate influence of man-made fossil fuels, which have caused the
atmosphere's CO2 levels to rise. "During some parts of the
last
century, as the amount of CO2 increased, the temperature
increased," he
explained. "I don't dispute that, and I'm not saying that
CO2 can't
have significant effects in the future.
"What I am saying is the data do not unambiguously support
the
contention that CO2 increases are the dominant cause of climate
variability," he added. "There are other reasons for
climate variations
that are significant. In fact, we've found that the strongest
correlation is the one between the area of the Sun's surface
covered
with holes and the globally averaged temperature of the
Earth."
Support for this research came from the Mount Wilson Institute
and the
Electric Power Research Institute, with additional funding from
the
Massachusetts Space Grant Consortium, the Smithsonian
Institution, the
Richard C. Lounsbery Foundation, and NASA.
# # #
Editors, please note: For a full-text version of the New
Astronomy paper,
click on http://www1.elsevier.com/journals/newast
.
For more information, contact:
* Dr. Eric Posmentier
Long Island University
718-780-4163, posmentier@mindspring.com
* Dr. Sallie Baliunas
Harvard-Smithsonian Center for Astrophysics
617-495-7415, sbaliunas@cfa.harvard.edu
* Dr. Willie Soon
Harvard-Smithsonian Center for Astrophysics
617-495-7488, wsoon@cfa.harvard.edu
=================
(4) A REVIEW OF COMET AND ASTEROID STATISTICS
T. Gehrels: A review of comet and asteroid statistics. EARTH
PLANETS
AND SPACE, 1999, Vol.51, No.11, pp.1155-1161
UNIVERSITY OF ARIZONA,TUCSON,AZ,85721
The statistics of Earth-approaching asteroids are first
summarized, and
an enhanced frequency of objects smaller than 100 meters is
noted.
Superposed on these random hazards may be a periodic one of new
comets
due to galactic tides of the Oort Cloud with a period of 26-36
Myr
(Rampino, 1998). New asteroids and comets are being found
evermore
frequently because new telescope-and-detector systems are coming
on
line. These are intended primarily for the discovery of dangerous
objects, but a beginning has been made with the study of
statistics of
main-belt asteroids. In addition to trans-Neptunian objects,
cis-Neptunian ''Centaurs'' are recognized, which may be a link in
the
evolution of short-period comets and thereby contribute to the
flux of
Earth approachers. With the new equipment coming on line, we are
beginning to see that the global hazard will be mostly quantified
within a few decades. We do see a shortage in astrometric follow
up
fainter than about the 20th magnitude. Copyright 2000, Institute
for
Scientific Information Inc.
==============
(5) ANGULAR MOMENTUM TRANSFER IN OBLIQUE IMPACTS
M. Yanagisawa*) & S. Hasegawa: Angular momentum transfer in
oblique
impacts: Implications for 1989ML. EARTH PLANETS AND SPACE, 1999,
Vol.51, No.11, pp.1163-1171
*) UNIVERSITY OF ELECTROCOMMUN,1-5-1 CHOFUGAOKA,CHOFU,TOKYO
1828585,JAPAN
We conducted 10 shots of high-velocity oblique impact experiments
(1.95-3.52 km/s) using nylon projectiles and spherical mortar
targets.
Large craters were formed, but these targets were not disrupted
by the
impacts. We then calculated the efficiencies of momentum transfer
from
the projectile to the post-impact target for each experiment. The
efficiencies of angular momentum transfer from the translational
motion
of the projectiles to the rotation of the post-impact targets
were also
derived. A representative efficiency of angular momentum transfer
was
calculated to be 0.17 for random successive collisions. The
efficiency
was applied to an equation expressing the precession angle of
asteroids. It is shown that 1989ML, target of Japan-US
asteroid-sample-return-mission (MUSES-C) would be tumbling.
Copyright
2000, Institute for Scientific Information Inc.
=============================
* LETTERS TO THE MODERATOR *
=============================
(6) CLARIFICATION
From Alan W. Harris <awharris@lithos.jpl.nasa.gov>
Dear Benny,
For once I have a matter which I specifically DO request that you
include in the next issue of CCNet. In today's issue, 14 March,
the
first three items are directly quotted from David Morrison's NEO
News.
You have given proper attribution for the first item, from
Morrison
himself, but failed to similarly note that the second item (by
Chapman)
and the third (by Harris) were likewise copied from the NEO News,
not
direct submissions to CCNet. Of course one who reads all of the
first
item will realize that, but I still feel you have potentially
misled
readers to conclude that my (and Clark's) commentary were
original to
CCNet. I therefore request that you post a clarification that the
item
from me was quotted from NEO News. In the future, at least for
any item
that was written by me, please include a careful citation of
source
from which you copied.
With best regards,
Alan Harris
==============
(7) A QUICK NOTE ON IMPACT EVENT RATES
From Ed Grondine <epgrondine@hotmail.com>
Hello Benny -
How damn convenient to declare that only 1 km and above asteroids
are hazardous, while completely ignoring impacts by comets and
impacts by asteroids less than 1 km. My list of suspected
impact
events running back to say 3000 BCE or so, as of March 2000, runs
something like this:
Class 8:
"A collision capable of causing localized destruction. Such
events
occur somewhere between once per 50 years and once per 1000
years."
Observed:
ca. 1584 BCE Destruction of Hittite forces under T'e Hantilish
(Joshua
impactor)
ca. 520 BCE Destruction of Etruscan town of Volsinii
679 AD - Destruction of Colingiham Monastery
ca. 800 AD - Impact in Baltic and death by local tsunami
ca. 1321-1368 AD Erh River fall in China
1450 AD - miss ("missed" people - no one killed) Wabar
1490 AD - Ch'ing-yang fall kills over 10,000 (possibly hail)
(I have temporarily misplaced that list of what, 8?, small events
of the
1700's and 1800's so laboriously assembled from obscure sources
by one
industrious researcher, and my apologies to him)
1868 AD - miss near Pultusk, Poland
1908 AD - miss in Tunguska
1930 AD - miss in Brazilian jungle
1947 AD - miss at Sikhote Ailin in Kamchatka
1972 AD - miss in South West Pacific
Class 9:
"A collision capable of causing regional devastation. Such
events
occur between once per 1,000 years and once per 100,000
years."
Observed:
ca. May 10, 2807 BCE - Masse sets this as the date of the Indian
Ocean
impact and resulting tsunami
580 AD - Destruction of Bordeaux region and city of Orleans
585 AD - Destruction of "two islands in the sea"
Date unknown - Destruction of Ainu
ca. 1400 AD? - Impact event leads to beginning of migration of
Lenape
(Bobk, what is the date here? Anything else you'd like to
add to this
list, like the death of the mammoths?)
ca. 1500 AD - Australian Great Wall of Water, with collapse of
Polynesian megalithic cultures on Ponhpei and elsewhere
Class 10:
"A collision capable of causing global climatic catastrophe.
Such
events occur once per 100,000 years, or less often."
Observed:
ca. 3114 BCE - Atlantic impact; Battle of Titans(?), tsunami
leading to
flood myths, Stonehenge I begins, Mayan Calendar begins;
ca. 2345 BCE - Ullikummi cometary impactor pretty much wipes out
Hurrians,
dust loading leads to climate collapse
ca. 2100 BCE - Rio Cuarto impactor and resulting climatic
collapse
ca. 1160 BCE - General migration in eastern Mediterranean follows
report by
observor from some distance away of loud noise and rush of air
ca. 536 AD - Dust loading leads to sub-Roman times
becoming sub-Roman
Now maybe all these are related to some one comet disintegrating,
or to
some one asteroid parent body, but I doubt it. May I politely
suggest
to the various NASA folks who did not manage to snag the NEO
center
that first, they stop being poor sports, and second, that they
take a
few moments to re-think exactly how important a manned flight to
Mars
is in light of the large numbers of people killed by these
earlier
impactors?
EP
==============
(8) FASTEST SPINNING ASTEROID?
From Charles F. Peterson <cfp@mcn.org>
In terms of useful information about NEAs, it would seem that the
velocity of the surface of the asteroid tells more than the
rotational
period. Am I correct?
The surface of a 100 meter asteroid with a rotational (day/night)
period of 10 minutes is not moving as fast at its equator as the
surface of a one kilometer asteroid with a much longer rotational
period. Surface velocity would tell something about origin
and impact
history, right? Day/night period seems to be an interesting but
inconsequential artifact of the relationship of diameter to
surface
speed.
==============
(9) DRAGONS IN THE SKY
From Neil Bone <bafb4@central.susx.ac.uk>
While much is made in many quarters of fireballs described as
'drakes'
or dragons, in some Chinese records, it might be equally possible
that
these references are also to auroral displays. The twisting,
serpentine
form of an auroral rayed band, for example, might as easily be
the
source of the cited reports here. Some years ago - I think it was
1981
- there was even the suggestion in New Scientist that St George's
dragon was actually an aurora... Not everything in the sky *has*
to be a
meteoric fireball!
Neil Bone
===================
(10) THE VIOLENT HABITAT OF EARLY TERRESTRIAL LIFE
From Stephen Ashworth <sa@astronist.demon.co.uk>
Dear Benny Peiser,
When Andrew Glikson claims "there is as much intelligence in
a bee
dance as in the Swan Lake ballet" (CCNet Essay, 13 Mar
2000), is he
gauging intelligence by IQ, or by evolutionary development time,
or by
brain mass, or by some other quantifiable yardstick?
Or is he claiming that the bee dance and the ballet (and, by
implication, such imminent developments as genetic engineering
and
panspermia via artificial spacecraft) were arrived at through the
same
kind of process?
Yours,
Stephen Ashworth
Fellow of the British Interplanetary Society
Webmaster, Space Age Associates
----------------------------------------
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