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(meteorobs) Excerpts from "CCNet DIGEST, 20 August 1999"
I thought the starting poem was well-selected this issue!
Lew
------- Forwarded Message
From: Benny J Peiser <b.j.peiser@livjm.acdot uk>
To: cambridge-conference@livjm.acdot uk
Subject: CCNet DIGEST, 20 August 1999
Date: Fri, 20 Aug 1999 11:34:32 -0400 (EDT)
CCNet DIGEST, 20 August 1999
----------------------------
POEM OF THE DAY (suggested by Rolf Sinclair)
I would rather be ashes than dust!
I would rather that my spark should burn out
in a brilliant blaze than it should be stifled by dry-rot.
I would rather be a superb meteor, every atom
of me in magnificent glow, than a sleepy and permanent planet.
The function of man is to live, not to exist.
I shall not waste my days trying to prolong them.
I shall use my time.
Attributed to Jack London (1876-1916).
[See <http://sunsitedot berkeley.dot edu/London/credo.html>.]
(1) AUGUST 15 BOLIDE IN SOUTHWEST US
Mark Boslough <mbboslo@sandiadot gov>
(2) NEW RADAR IMAGES OF ASTEROID 1999 JM8
Ron Baalke <baalke@ssd.jpl.nasadot gov>
(3) RICHES IN THE RUBBLE OF THE SOLAR SYSTEM
Michael Paine <mpaine@tpgi.com.au>
...
=============
(1) AUGUST 15 BOLIDE IN SOUTHWEST US
>From Mark Boslough <mbboslo@sandiadot gov>
We captured a bright fireball on videotape Sunday evening August 15
at 11:18 PM local time in Albuquerque, NM (05:18 UT). Our radiometer
showed a peak magnitude of about -16.5. The object was due west of
Albuquerque. We estimate the range to be about 300 km based on our
elevation angle and eyewitness reports from El Paso, TX. The absolute
(100 km) magnitude is therefore about -19. The worldwide mean
frequency of bolides of this brightness is 10 to 20 per year.
Comparison to Ceplecha's data suggest a pre-atmospheric mass on the
order of one ton. There were intense thunderstorms over NW New Mexico
and NE Arizona at that time, so it is unlikely that a precise
trajectory will be determined. Our video is avaliable on the web
at http://www.cs.sandiadot gov/SEL/apps/energy/meteor.htm
Mark Boslough
Richard Spalding
==================
(2) NEW RADAR IMAGES OF ASTEROID 1999 JM8
>From Ron Baalke <baalke@ssd.jpl.nasadot gov>
Recently discovered asteroid 1999 JM8 passed within 0.06 AU from the
Earth on July 30, 1999. Using the Goldstone Deep Space Network antenna
and the Arecibo Observatory, a team led by Steve Ostro from JPL were
able to bounce radar off of this asteroid. The radar images obtained
from August 1-9 are available here:
http://neo.jpl.nasadot gov/images/1999jm8.html
Ron Baalke
================
(3) RICHES IN THE RUBBLE OF THE SOLAR SYSTEM
>From Michael Paine <mpaine@tpgi.com.au>
Hi Benny, welcome back.
Here is the text on the latest article in my new column at
Explorezone. I wrote it after reading "Mining the Sky" by John Lewis.
http://explorezone.com/columns/space/1999/august_neo_mining.htm
Riches in the rubble of the solar system
By Michael Paine for explorezone.com
Thirty years ago, when the Apollo astronauts brought rocks back from
the Moon, nobody rushed to stake a mining claim. Only traces of
useful materials were found. The surface of the Moon turned out to be
barren and unattractive for commercial development.
Asteroids, however, are another matter. Nearly all the raw materials
needed to build a self-sufficient space colony are available on the
most common type of asteroid. NASA plans to land a small robotic
spacecraft on an asteroid within a few years, just one example of the
belief that asteroids are both accessible and worth exploring.
Recipe for a solar system
Most asteroids are made from the raw ingredients of the solar system,
researchers believe. Those ingredients came from supernova --
exploding overweight stars. The solidified debris from these
explosions contains mainly dust, rocks, water ice and iron (actually
an alloy of iron, nickel and cobalt -- a natural stainless steel).
Nearly 5 billion years ago, under the tug of gravity, debris from
supernovas gathered into a spinning disk. Most of this material fell
into the center of the disk and formed our Sun. Further out the
material formed many planets. As these planets circled the Sun they
collided with each other and grew larger, until just nine planets
were left. The debris from these collisions, together with other
leftover rubble, was either swallowed up in further collisions or was
mostly herded into planet-free zones like the asteroid belt between
Mars and Jupiter.
Blast-furnace planets
The inner planets (Mercury, Venus, Earth and Mars) likely started off
as hot balls of molten metal and rock.. Like a blast furnace used for
making iron, most of the metal sank to the center of each planet and
a thin, rocky crust formed on the surface. The crust material of
these planets generally has much less metal than the raw ingredients
of the solar system. Most crust is the equivalent of the slag, or
discard, from a blast furnace, and there are just a few places near
the Earth's surface where metal ores are concentrated enough to make
mining worthwhile.
The good stuff is deep within Earth's interior.
Riches in the rubble
Solar system rubble still collides with the Earth -- the smaller
rocks reach the ground as meteorites. Some meteorites are nearly pure
stainless steel, born in ancient supernovas.
Most of the asteroids are made of the same stuff as meteorites. They
too are rich in useful metals and chemicals such as water and carbon,
and hence their commercial potential.
An example of the possible riches amongst this rubble of the solar
system is the asteroid Amun. The orbit of this mile-wide object comes
close to the Earth's orbit and, over millions of years, it could be a
threat to the Earth. Before then, however, it is likely that mankind
will have visited the asteroid and mined it away to nothing, because
research indicates Amun is made from that primordial stainless steel.
Planetary Scientist John Lewis, from the University of Arizona,
estimates that the iron, nickel and cobalt in this single asteroid is
worth about $20,000 billion at market prices.
Amun is unusually rich in metals and is typical of perhaps only 5
percent of asteroids. Most asteroids contain more rock than metal, but
at least half of the material in these so-called stony asteroids could
also be put to human use.
Let the asteroids come to us
Some half a million asteroids 100 yards across or larger orbit the
Sun along paths that cross or come close to the orbit of the Earth.
In principle, it is easier to reach about 100,000 of these "Near
Earth Asteroids" and return a payload to the Earth than it is to
return the same payload from the Moon.
The recent Deep Space 1 flyby of asteroid Braille showed that we have
the space technology to reach Near Earth Asteroids. By using material
mined in space, mission planners could avoid the very high cost of
launching materials from Earth.
The biggest technical difficulty in mining solid metal asteroids such
as Amun might be the task of chopping chunks of metal from the main
block. On Earth we have never had the luxury of mining a giant lump
of pure stainless steel, so we don't even know how to do it.
Still, there is plenty of iron in common asteroids that could be
mined using conventional techniques. These asteroids also contain
water, which is not only important for surviving and manufacturing in
space but also has potential as a rocket propellant.
A new steam-powered "Rocket"
In 1829 George Stephensen won the first ever railway competition with
a steam engine called the "Rocket." Although steam engines have now
gone out of style on the surface of the Earth, there is great potential
for steam-powered rockets in space.
In the vacuum of space a craft produces thrust by shooting matter at
high speed out an exhaust portal. Conventional rockets burn exotic
chemicals and the combustion products are forced out of a rocket
nozzle to produce thrust.
An alternative to a chemical rocket is to heat a volatile material (a
material which readily forms a gas) and expel the resulting
superheated gas from the rocket chamber. The natural choice for this
expendable material is water. Possible sources of heat are nuclear or
solar power.
The main obstacle to steam powered rockets is the cost of launching
tons of water into space from the Earth's surface. At a current cost
of thousands of dollars per pound launched, we might as well send
exotic chemicals into space -- the cost of the material becomes
irrelevant.
But what if we could obtain water in space? The Moon's polar regions
are suspected of holding frozen water, but the lunar poles are
difficult to reach and launching payloads from the Moon is
technologically and economically difficult. The obvious source of
water is Near Earth Asteroids, because asteroids typically contain 10
to 20 percent water in the form of permafrost or saturated minerals.
Dormant comets also orbit the Sun near the Earth, and these "dirty
snowballs" likely contain more than 50 percent water.
There is another advantage to using water in space rockets. A thick
layer of water ice around a manned spacecraft makes an excellent
shield from radiation and small meteoroids. Water storage tanks could
surround the habitable modules of spacecraft, like igloos in space.
The next giant leap for Mankind
Our Earth-based technology for mining and processing raw materials
needs to be adapted for use in space -- for mining the asteroids. If
the dreams of science fiction writers are to become a reality and
humans are to colonize space, then the next step is to tap into the
vast resources of the rubble of the solar system.
Copyright 1999, Explorezone
...
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