PLEASE NOTE:
*
CCNet DIGEST, 24 November 1998
------------------------------
(1) LEONIDS SAMPLE RETURN PAYLOAD HAS BEEN FOUND
Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
(2) FIRST DIRECT DETECTION OF METEORITE IMPACTS ON SATURN RINGS
Andrew Yee <ayee@nova.astro.utoronto.ca>
(3) WHO INVENTED DEFLECTION IDEA?
Duncan Steel <dis@a011.aone.net.au>
wrote:
(4) WHO INVENTED DEFLECTION IDEA?
Bob Kobres <bkobres@uga.edu>
(5) A COUPLE OF COMMENTS
Gerrit Verschuur <GVERSCHR@MOCHA.MEMPHIS.EDU>
(6) THE GEMINIDS ARE COMING
Robert Lunsford <lunro.imo.usa@prodigy.com>
(7) OBSERVING METEOR PHENOMENA & BODIES
Z. Ceplecha et al., UNIVERSITY OF ADELAIDE
===============
(1) LEONIDS SAMPLE RETURN PAYLOAD HAS BEEN FOUND
From Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
Marshall Space Flight Center
http://science.nasa.gov/newhome/headlines/ast23nov98_1.htm
Scientists are examining the aerogel 'comet-catcher' for traces
of
Leonid meteoroids
November 23, 1998: The Leonids Sample Return payload has
been
recovered. It was pinpointed by amateur balloon trackers on
November
18th, and rescued from a briar patch in Chatsworth, Georgia in
good
condition.
The balloon was launched on November 17th during the Leonids
meteor
shower by scientists at NASA's Marshall Space Flight Center. It
carried
a CCD video camera to record the shower for a live webcast, as
well as
a device designed to capture Leonid meteoroids and return them to
Earth
intact. The "Comet Catcher" is a matrix of
aerogel-filled wells
(similar to Petri dishes) that were fixed to the outside of the
balloon
package. The payload was carried to an altitude greater than
100,000
feet, above 98% of Earth's atmosphere, during a flight that
lasted 1
hour 54 minutes. At its maximum altitude the balloon ruptured,
according to plan, and the payload descended to Earth by
parachute for
a relatively gentle landing in Georgia.
The aerogel sample collectors have been returned to scientists at
the
NASA Marshall Space Sciences Lab, where they are being examined
with an
environmental scanning electron microscope for evidence of
meteoroids.
Bill Brown (WB8ELK) contributed this account of the recovery:
"Today (Nov. 18th), Melody Johnson and pilot Don Henson flew
over
Chatsworth, Georgia and pinpointed the landing site by homing in
on the
144.000 MHz tracking signal coming from the balloon. Melody used
a ham
radio unit supplied by Randy Ware, director of the technology
center of
Dalton Junior High School."
"As soon as they landed, Melody drove to the area and homed
in on the
signal and stopped in front of Homer's Yarn and Textile Sales
when the
radio signal became very strong. After explaining the situation
(Quote:
'NASA needs YOU!!'), owner Homer Dills walked behind his
warehouse and
found the payload lying in a briar patch just behind the
building. The
payload is in excellent condition and the strobe lamp was still
flashing."
"The landing site is just off of Old Dalton Ellijay Road
about 1.6
miles due west of downtown Chatsworth, Georgia. Coordinates: 34d
46.19m
N, 84d 47.90m W."
=====================
(2) FIRST DIRECT DETECTION OF METEORITE IMPACTS ON SATURN RINGS
From Andrew Yee <ayee@nova.astro.utoronto.ca>
Stanford University
CONTACT: David F. Salisbury, News Service
(650) 725-1944, e-mail: david.salisbury@stanford.edu
COMMENT: Mark Showalter, STAR Lab
(650) 604-3382, e-mail: showalter@Ringside.Arc.Nasa.Gov
11/6/98
First direct detection of meteoroid impacts on Saturn rings
Movies like "Deep Impact" and "Asteroid" have
popularized the notion
that the solar system contains kilometer-wide chunks of material
that
represent a potential hazard to life on Earth.
But how many of these objects actually lurk in the darkness of
space?
Mark Showalter's research may help answer that question. A
research
associate at Stanford's Space, Telecommunications and
Radioscience
Laboratory (STARLab) who works out of the NASA Ames Research
Center,
Showalter reports, in the Nov. 6 issue of the journal Science,
the
first direct and unambiguous detection of basketball-sized
meteoroids
striking one of Saturn's rings.
Using images taken by the two Voyager spacecraft that flew by the
ringed planet in 1980 and 1981, Showalter identified objects that
he
calls "burst events" on the F Ring, a faint and narrow
ring that orbits
about 3000 kilometers beyond the outer edge of Saturn's main ring
system.
By tracking these bursts long enough to determine that they have
a
lifetime of about two weeks, he determined that they are clumps
of dust
kicked out of the ring when it is hit by small meteoroids ranging
from
two to 40 centimeters in size.
The F Ring has the best conditions for allowing observation of
these
dust clouds, Showalter says. It is dim enough so that the clumps
show
up and thin enough so that they do not rapidly collapse back into
the
ring. That allowed him to follow the evolution of three of these
clumps
in some detail. Their spreading rates were consistent with that
expected if the ring was hit by an object traveling at high
velocity,
he reports.
Showalter estimates that the F Ring experiences about 20 such
impacts
per year. This, in turn, allowed him to produce the first crude
indication of the abundance of centimeter-sized objects in the
outer
solar system. When the Cassini spacecraft reaches Saturn in 2004,
it
will be equipped to do a more thorough job of observing these
impacts
and so should provide a much more precise estimate, he says.
There are only two other sources of data about meteoroids in the
solar
system's outer reaches. The Pioneer 10 and 11 spacecraft, which
flew by
Saturn in the late 1970s, were equipped with a simple detector
that
provided an estimate of the population of micrometer-sized
particles in
the vicinity of Jupiter and Saturn. Observations with Earth-based
telescopes also have discovered eight asteriods in the 10- to
100-kilometer size range that cross Saturn's orbit. They have
been
named the Centaurs.
Such research should give scientists a better handle on the
number of
meteoroids of various sizes that exist in the inner solar system.
Objects of this size strike the Earth fairly frequently. They are
large
enough so that they don't completely burn up in the atmosphere,
and the
burnt remnant lands on Earth as a meteorite. But they are too
small to
be picked up in satellite imagery, so the frequency of these
fiery
collisions is not well known, Showalter says.
"People who model these things estimate that the frequency
of
meteoroids should be about the same throughout the solar
system," he
says. And, within the rather large uncertainties involved, his
observations are consistent with that assumption.
More importantly, improved knowledge of the abundance of
centimeter-sized meteoroids in the solar system will provide
better
estimates of the numbers of kilometer-sized objects, which are
the real
concern.
"It is all part of a continuous process," Showalter
says. "We know
there are so many ping-pong-ball-sized objects for every
basketball-sized object and so many basketball-sized objects for
every
house-sized one. So improved estimates of meteoroids of any given
size
improve our estimates of the number of meteoroids of all
sizes."
================
(3) WHO INVENTED DEFLECTION IDEA?
From Duncan Steel <dis@a011.aone.net.au>
wrote:
Dear Benny,
Richard Kowalsky asked:
>...when was the idea of deflecting a possible impactor first
put forward
>and by whom?
The idea goes back to at least the early 1950s (i.e., before the
Space
Age began). As I mention in my book 'Rogue Asteroids and
Doomsday
Comets', in their book entitled 'Target: Earth' (1953) Allan
Kelly and
Frank Dachille wrote about the need to deflect or destroy
asteroids on
a collision course with our planet, in vivid terms. I give
a more
detailed description of their writing and its context in:
D. Steel, The death of the dinosaurs and protection of humankind
from
asteroid impacts: the first suggestion? Australian Journal
of
Astronomy, 6, 87-90 (1995).
Sorry, I do not have reprints available for dissemination, but
that
now-defunct journal is held by various specialist libraries (such
as at
the Royal Astronomical Society in London, and the University of
Oxford
Astrophysics library).
Duncan Steel
============
(4) WHO INVENTED DEFLECTION IDEA?
From Bob Kobres <bkobres@uga.edu>
In regard to Richard Kowalsky query (11/23/98 CC-Debate) about
the idea
of asteroid deflection, this will at least place the origin of
the idea
back beyond three decades.
From:
http://abob.libs.uga.edu/bobk/nicc.html
In July of 1966, United Press International (UPI) fed to
newspapers
around the world this short report:
SYDNEY, Australia (UPI) --An Australian scientist says if an
asteroid
now speeding toward the earth veered just slightly, it would
crash into
the planet with the impact of 1,000 hydrogen bombs.
Prof. S.T. Butler, professor of theoretical physics as Sydney
University, made the statement in an interview with the Sydney
Telegraph.
He said the asteroid known as Icarus was speeding toward the
earth at
70,000 miles per hour and was expected to pass four million miles
away
in 1968.
"If Icarus hit the earth, it would be like the explosive
power of 1,000
hydrogen bombs," Butler said. He added that four million
miles away
from the earth was "only a stone's throw for outer space.
Butler said scientists in the United States, Britain and the
Soviet
Union were closely studying the elliptical orbit of the asteroid.
He
said it could possibly be destroyed with a high-altitude rocket
armed
with a nuclear head if it neared the earth.
"It sounds fantastic," Butler said, "but we could
land a rocket with
pinpoint accuracy 50 million miles away and destroy it. This is
where
billions spent on space research pays off."
He said the scientists were keeping close tabs on the asteroid.
Butler said scientists feared that if the asteroid altered its
course a
fraction of a foot, it would come within the earth's
gravitational
pull.
-------------
Butler's suggestion that nuclear tipped rockets could be used to
prevent such a collision inspired M.I.T. professor Paul Sandorff
to
assign, as a hypothetical problem for his systems engineering
class, a
detailed study of just how to go about this. "Project
Icarus," as the
study come to be called, drew quite a bit of attention itself.
Time
magazine ran an article on the endeavor in June of 1967 and the
following year the class study was published as a book--Project
Icarus--which is unusual for a student project. In this book the
reader
can find these revealing lines:
"The consequences of a collision with Icarus are
unimaginable; the
repercussions would be felt the world over. In dissipating the
energy
equivalent of half a trillion tons of T.N.T., 100 million tons of
the
Earth's crust would be thrust into the atmosphere and would
pollute the
Earth's environment for years to come. A crater 15 miles in
diameter
and perhaps 3 to 5 miles deep would mark the impact point, while
shock
waves, pressure changes, and thermal disturbances would cause
earthquakes, hurricanes, and heat waves of incalculable
magnitude.
Should Icarus plunge into the ocean a thousand miles east of
Bermuda
for example, the resulting tidal wave, propagating at 400 to 500
miles
per hour, would wash away the resort islands, swamp most of
Florida,
and lash Boston -- 1500 miles away -- with a 200-foot wall of
water".
"In light of the consequences of a collision with an
asteroid the size
of Icarus, the possibility of such a collision, no matter how
remote,
cannot go unrecognized. The world must be prepared, at least with
a
plan of action, in case it should suddenly find itself threatened
by
what had so recently been considered a folly".
The words ". . . threatened by what had so recently been
considered a
folly" are most indicative of the alteration in world view
taking place
in this decade of change. Gradualism was doomed--the writing was
on the
wall. A little over a decade later hard evidence extracted from
clay
covering the dinosaurs would be on the table. Interestingly the
1979
discovery of the now famous iridium anomaly by the Alvarez team
coincides with the Hollywood release of the movie Meteor, in
which
Earth is saved from a five-mile-across meteoroid by the combined
strength of U.S. and Soviet nuclear forces. The film was inspired
by
"Project Icarus."
Bob Kobres
Main Library
University of Georgia
Athens, GA 30602
bkobres@uga.edu
706-542-0583
http://abob.libs.uga.edu/bobk
=====================
(5) A COUPLE OF COMMENTS
From Gerrit Verschuur <GVERSCHR@MOCHA.MEMPHIS.EDU>
Liverpool played a great game Saturday, unlike Man U> we get
2 hours of English soccer on TV every Sunday and see all the
goals
from the premier league.
Dr Andrew Glikson wrote "it is well known that the
distinction between
organic matter and bacterial life forms is not a quantitative one
but a
qualitative quantum jump."
The media in the USA often use the quantum leap expression as did
President George Bush in some context during a presidential
campaign,
but no one seems to realize that a quantum jump is not only
discrete
but also very, very, very small.
Gerrit Verschuur
=====================
(6) THE GEMINIDS ARE COMING
From Robert Lunsford <lunro.imo.usa@prodigy.com>
For information on the Geminids and other meteor showers check
out the
following web sites:
http://medicine.wustl.edu/~kronkg/namn/guide..html
http://medicine.wustl.edu/~kronkg/index.html
http://www.imo.net
Clear Skies!
Bob Lunsford
==========
(7) OBSERVING METEOR PHENOMENA & BODIES
Z. Ceplecha*), J. Borovicka, W.G. Elford, D.O. Revelle, R.L.
Hawkes, V.
Porubcan, M. Simek: Meteor phenomena and bodies. SPACE SCIENCE
REVIEWS, 1998, Vol.84, No.3-4, pp.327-471
*) UNIVERSITY OF ADELAIDE, DEPT PHYS & MATH PHYS, ADELAIDE,
SA 5001, AUSTRALIA
Meteoroids can be observed at collision with the Earth's
atmosphere as
meteors. Different methods of observing meteors are presented:
besides
the traditional counts of individual events, exact methods yield
also
data on the geometry of the atmospheric trajectory; on the
dynamics and
ablation of the body in the atmosphere; on radiation; on the
spectral
distribution of radiation; on ionization; on accompanying sounds;
and
also data on orbits. Theoretical models of meteoroid interaction
with
the atmosphere are given and applied to observational data.
Attention
is paid to radar observations; to spectroscopic observations; to
experiments with artificial meteors and to different types of
meteor
sounds. The proposed composition and structure of meteoroids as
well as
their orbits link them to meteorites, asteroids and comets.
Meteor
streams can be observed as meteor showers and storms. The rate of
influx of meteoroids of different sizes onto Earth is presented
and
potential hazards discussed. Copyright 1998, Institute for
Scientific
Information Inc.
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