PLEASE NOTE:
*
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://sunsite.berkeley..edu/London/credo.html>.]
(1) AUGUST 15 BOLIDE IN SOUTHWEST US
Mark Boslough <mbboslo@sandia.gov>
(2) NEW RADAR IMAGES OF ASTEROID 1999 JM8
Ron Baalke <baalke@ssd.jpl.nasa.gov>
(3) RICHES IN THE RUBBLE OF THE SOLAR SYSTEM
Michael Paine <mpaine@tpgi.com.au>
(4) RUSSIA SAYS U.S. IS PLANNING A NUCLEAR RACE IN SPACE
SPACE.COM <thoughts@SPACE.COM>
=============
(1) AUGUST 15 BOLIDE IN SOUTHWEST US
From Mark Boslough <mbboslo@sandia.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.sandia.gov/SEL/apps/energy/meteor.htm
Mark Boslough
Richard Spalding
==================
(2) NEW RADAR IMAGES OF ASTEROID 1999 JM8
From Ron Baalke <baalke@ssd.jpl.nasa.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.nasa.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
==============
(4) RUSSIA SAYS U.S. IS PLANNING A NUCLEAR RACE IN SPACE
From SPACE.COM <thoughts@SPACE.COM>
Rather than declaring renewed friendship with the United States,
Russia walked away from new arms control talks on Thursday,
accusing
Washington of trying to start a new nuclear arms race in outer
space.
http://www.space.com/news/international/russia_warning_819.html
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DEEP IMPACT
Mark Bailey's report from the IMPACT meeting, Turin 1-4 June
ASTRONOMY & GEOPHYSICS: The Journal of the Royal Astronomical
Society,
Vol 40 Issue 4, August 1999, pp. 25-26*
-----------------------------------------------------------------------
*The permission of the editor of A&G to circulate this
article on CCNet
is gratefully acknowledged.
-----------------------------------------------------------------------
Astronomers representing space agencies and other groups with
interests
in the international Spaceguard programme met in Turin from 1-4
June
1999 for the meeting "International Monitoring Programs for
Asteroid
and Comet Threat (IMPACT)". Plenary sessions reviewed
current survey
programmes and associated scientific and policy issues thrown up
by the
recent greatly enhanced discovery rate of Near-Earth Objects
(NEOs);
sub-groups hammered out recommendations and procedures for future
implementation. The agreed resolutions will be taken forward with
governments and funding agencies, and international bodies such
as the
International Astronomical Union.
Background
The IMPACT workshop to review progress towards establishing an
international programme to detect - and if necessary deflect -
any
incoming asteroid or comet with the potential to destroy
civilization
or threaten life on Earth, was not the first such meeting. It
followed
a meeting on the Mediterranean island of Vulcano in September
1995.
The IMPACT meeting, sponsored by bodies including the
International
Astronomical Union (IAU), the Planetary Society, the
Spaceguard
Foundation, the Italian Space Agency (ASI), and both NASA and
ESA,
included representatives from virtually all the organisations
currently
carrying out major work in this area. Six of the seven
principal
observational groups were represented, as too were all the teams
presently involved in handling the vast increase in orbital data
and
other information for astronomers worldwide.
The rapid progress in this area is best illustrated by the
success of
the Massachussetts Institute of Technology/Lincoln Laboratory
programme
LINEAR (Lincoln Near Earth Asteroid Research), at the
experimental test
site on the White Sands Missile Range in Socorro, New Mexico. The
Lincoln survey, largely funded by the United States Air Force,
uses a
wide-field, rapid read-out CCD on a military GEODSS (Ground-based
Electro-Optical Deep Space Surveillance) 1-metre telescope,
capable of
reaching a limiting magnitude of ~22 on a 2 square degree field
of view
in less than 100 seconds integration time. The system has been
operating with the wide-field CCD since March 1998, in which time
it
has already discovered more than 200 of the 700 or so known NEOs,
and
has produced - in that time alone - more than a five-fold
increase in
the workload of the IAU Minor Planet Center (MPC), representing
more
than a million astrometric observations. The programme will
shortly be
joined by a second GEODSS telescope, operating at the same site,
and
is expected to produce a second step-increase in the rate of
discovery.
Lost and found
One of the main themes of the meeting concerned the question how
to
handle the vastly increased number of asteroid detections, and
how to
ensure that the asteroids, once found, are not subsequently lost
due to
lack of suitable follow-up. The MPC, originally set up to
coordinate a
moderate rate of discovery of comets and minor planets, needs
additional resources to cope with the extra demands of an order
of
magnitude increase in data throughput. A further factor is the
increasing demands of users of the MPC service, who sometimes
require
essentially instantaneous access to new discoveries, rapid
computation
of orbital data and projections, and information on where other
survey
telescopes are looking, both to maximize the overall survey
efficiency
and the chance that an asteroid, once detected, will not be lost.
Increasingly, it is clear that wide-field survey programmes able
to
discover many so-called "small" solar system objects
should support the
desired central facilities, such as the Spaceguard Central Node
and the
Minor Planet Center. A proper survey should also incorporate the
relatively low cost of follow-up facilities to ensure that
initial
detections are not lost.
What are NEOs?
The second broad area of discussion focused on the programmes
necessary
to achieve complete physical characterization of the NEO
ensemble, both
comets and asteroids. Only by this means can a full understanding
of
the origin of NEOs be achieved (e.g. the respective proportions
originating via collisions in the main asteroid belt or through
the
evolution and possible break-up of comets). Such information
would also
be necessary in order to deflect such objects prior to possible
impact
with the Earth, should our generation be both u n l u c k
y enough to
be alive when a major impact is due and l u c k y
enough to discover
the projectile before it discovers us.
These astronomical programmes require spectrophotometric
observations
of asteroids and cometary nuclei with the objective of
identifying bulk
properties of the solid body such as mineralogical composition
(e.g. in
comparison with interplanetary dust particles, meteorites or
main-belt
asteroids), shape, spin axis, rate of rotation, density, and
whether
the structure is monolithic, or (possibly more likely)
rubble-pile.
These types of observations provide ground truth for the size
distribution of NEOs, their relationship to the planetary
building
blocks called planetesimals, and their respective
interrelationships
with other members of the Sun's extended family of small bodies.
Such
information is also essential if any NEO is to be deflected.
Access to a wide range of astronomical telescopes in the 2--10 m
class
will be required over the next decade to carry out these
visual/infrared programmes, as too will data from planned space
missions over the next few years. As was pointed out by Don
Yeomans
(Director of the NASA/JPL NEO Program Office), solar system
astronomy
is now entering a new golden age, with spacecraft going to 13
separate
comet or asteroid targets in as many years. Within this
time-frame it
is likely that our knowledge of such small bodies will go through
a
revolution as profound as that of the first phase of solar system
exploration, which resulted, in the late 1960s, in recognition of
the
extraterrestrial impact hazard in the first place.
The announcement dilemma
The third, and possibly the most contentious, focus of the
meeting
attempted to deal with the responsibility of astronomers, as
professional scientists and citizens, regarding the collision
hazard.
For example, what procedures should be in place prior to the
announcement of a possible impact (e.g. enhanced peer-review),
and then
who should be informed, how quickly, and at what stage should the
information be placed in the public domain and the media
involved? It
is obvious that as the present survey programmes get fully into
their
stride, the so-called "announcement dilemma" will
become an increasing
problem.
Several objects have non-zero probabilities of impact with the
Earth
within the next 50-100 years. The values (all low) will likely be
revised downwards in the light of further observations, but the
number
of such cases is bound to increase.
The difficulty is that whereas premature announcement might lead
to a
culture of false alarms and the accusation of "crying
wolf" (not to
mention possible panic amongst vulnerable members of the public),
the
lack of an early announcement might lead to a situation where the
warning of a real impact was not made in earlt enough for
effective
mitigation.
The media, of course, love this. Headlines can almost always be
guaranteed announcing the (possible) end of the world, while on
the
back of this genuine public interest, a serious programme of
public
understanding of science - spanning the whole range of
Spaceguard-related topics - could be developed.
A recent example shows how difficult it is to control the
monster.
Earlier this year, everyone agreed that the asteroid 1999 AN10
could
not possibly hit the Earth in 2027, despite the likelihood of an
exceptionally close approach. (Caveats, for example, included
whether
the object might be a comet and could suddenly start outgassing,
or
might hit an interplanetary boulder that changed its path, or any
number of possible low-probability scenarios.) The splash in a UK
newspaper The Sunday People, however, reported: "At 7.42
a.m. on August
7, 2027 the world will come to an end ... that's if the boffins
have
got it wrong by 9 minutes!"
Scientists are caught - almost literally - between a rock and a
hard
place. The announcements have to be made, else they are
accused of
censorship or - worse - a cover up, leading to loss of trust in
so-called experts. But the issue is also potentially serious,
involving
issues of national concern (which could diverge for different
nations),
even the future of civilization. Such discussions should not
occur
entirely in the rarefied atmosphere generated by
self-selected experts.
An impact hazard index?
One problem, succinctly expressed by David Morrison (NASA Ames,
and
Chair of the IAU Working Group on NEOs), is that "people
just don't
understand probability". In particular, people do not
understand how
to respond to the aired possibility of low-probability,
high-consequence events, and it was therefore suggested that the
information should be presented in a simpler way.
One proposal, presented by Rick Binzel (MIT), was to use an
impact
hazard index, in which events occuring with a probability
comparable to
the annual background rate for a similar-size object would
receive a
hazard index of 0 or 1, implying that they are "down in the
noise" and
therefore not worth getting concerned about. Higher impact
probabilities for the same size object would receive a higher
index,
on a scale 2-10, with 10 denoting the virtually certain impact of
the
canonical 10 km diameter dinosaur-killer.
A possible difficulty with this approach is that it demotes the
background impact rate to a level of insignificance, when in fact
it
is the s i g n i f i c a n c e of background impacts,
in comparison
with other possible environmental disasters, that makes the
asteroid
impact hazard unique.
A second possible difficulty is that in practice most discussions
are
likely to revolve around whether a particular object is a
"one" or a
"two", making largely redundant the precise and
detailed definition of
an impact hazard scale extending, for public consumption, over
the full
range 0-10. Although there was general agreement that a way has
to be
found to communicate results to the public in an accurate and
effective
way, it would appear that the proposed "Turin Impact
Scale" is at once
too simple-minded and too complicated.
An alternative solution, namely better education of the general
public
in the finer points of impact probabilities at the ~10^-5 per
annum
level (i.e. comparable to the annual probability of the Earth
being
struck by a kilometre-sized body with attendant global
consequences
involving billions of deaths), has many attractions, not least
its
application to other spheres of public policy. For example,
low-probability events killing "only" a few hundred
people at the
~10^-5 per annum level, are already assessed - and mitigated - by
government agencies across a wide range of health and
environmental
areas, because they are deemed intolerable. At the other
extreme,
governments are occasionally forced into making unplanned
expenditure
and policy shifts, simply because the public has failed to
appreciate
that a much lower annual risk of disaster (e.g. at the 10^-9
level) is
normally regarded as tolerable. Examples such as BSE or GM foods
are no
doubt debatable, but a vigorous programme of public understanding
of
science in this area could be beneficial.
Conclusions
The workshop was notable for the spirited, sometimes heated
debates on
these issues, and some memorable contributions from the floor.
The
participants agreed several resolutions for consideration by
government
departments and funding agencies. In particular, given that a
vigorous
start to the Spaceguard programme has now been made by one
nation,
namely the USA, contributions by other nations with relevant
expertise,
especially those in Europe or with access to the southern sky,
would be
particularly welcome.
In fact, the meeting recognized that only in this way will a
genuine
i n t e r n a t i o n a l programme be generated, allowing
the full
objectives of the Spaceguard survey, namely to identify and
characterise any large asteroid or comet due to impact the Earth
within the next century, to be achieved within the next twenty
years.
European astronomers have an important role to play.
Mark E. Bailey, Armagh Observatory
Copyright 1999, Astronomy & Geophysics
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copyright holders. The fully indexed archive of the CCNet, from
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