PLEASE NOTE:
*
CCNet DIGEST, 24 May 1999
-------------------------
Eros revisited
Some sixty years ago I was a boy who read a comic
book;
'Buck Rogers', invention of Dick Calkins, Lieutenant
in the navy.
Buck in his rocket ship went to explore an asteroid.
Eros was its name, about that time well-publicised
because astronomers were using it to find the solar
parallax,
a technique important then but long since
superseded.
Eros was known to be peculiar; it was long and thin,
not round
like planets ought to be. Well, you guess the rest,
that asteroid
was an enormous spaceship, abandoned aeons ago
(though not by dinosaurs, I think!) and filled with
wonders.
At Christmas '98 the pioneering NEAR passed Eros.
Its cameras turned to snap a few blurred views as
engine failure
made it pass too fast and have to wait another
year to stop.
But still, there in the frames was Eros, elongated,
cratered,
no space ship, but still a spaceflight triumph, not
for Buck
but for all those who grew up with the dream of
exploration.
The boy who read that comic book so long ago
exulted,
because he felt he'd shared in this great space
adventure.
22.5.99
Malcolm Miller
<stellar2@actonline.com.au>
(1) US CONGRESS INCREASES NASA'S NEO SEARCH BUDGET BY 200%
Benny J Peiser <b.j.peiser@livjm.ac.>
(2) LEONID METEOR IMPACTS ON MOON CREATE CLOUD OF SODIUM GAS
Harvey Leifert <HLeifert@agu.org>
(3) PASEG TALK ON SPACEGUARD & THE IMPACT HAZARD
Mark Bailey <meb@star.arm.ac.uk>
(4) SPACE ROCK HINTS AS EARLY ASTEROID FURNACE
INSCiGHT, 20 May 1999
(5) RAMBLING ASTEROID TO PASS CLOSE IN '27
San Jose Mercury News, 21 May 1999
(6) COULD ASTEROID 1999 AN10 BE USED FOR SPACE OBSERVATORY?
Elton L. Jones <jonee@epix.net>
(7) THE IMPACT HAZARD & SCIENCE EDUCATION FOR CHILDREN
Malcolm Miller <stellar2@actonline.com.au>
(8) THE MOON MAKER AVAILABLE ONLINE
Bob Kobres <bkobres@arches.uga.edu>
(9) MISSILE DEFENSE TO BE TESTED TOMORROW
The New York Times, May 24, 1999
(10) WHIPPLE'S NEW PAPER ON COMET NUCLEI
F.L. Whipple, CTR ASTROPHYSICS,
CAMBRIDGE, MA
(11) COMETARY SPLITTING DUE TO THERMAL STRESSES
L.V. Tambovtseva & L.I. Shestakova,
RUSSIAN ACADEMY OF SCIENCE
(12) PHOTOMETRIC OBSERVATIONS OF ASTEROID 85 IO
A. Erikson et al., DLR,INSTITUTE OF
PLANETARY EXPLORATION
===============
(1) US CONGRESS INCREASES NASA'S NEO SEARCH BUDGET BY 200%
From Benny J Peiser <b.j.peiser@livjm.ac.>
Last Wednesday, the American Congress considered and passed H.R.
1654,
the National Aeronautics and Space Administration Authorization
Act of
1999, authorizing the financial budget for the fiscal years 2000
to 2002. After many years of public criticism and lobbying, the
US
Congress has finally agreed to significantly increase NASA's NEO
search
budget. This is very good news. The NASA Authorization Act of
1999
increases the funding for the NEO survey by $7 million per year,
thus
bringing it to a total of &31.5 million for the next three
years. By
adding $7 million to the NASA survey budget per year, search
programmes
can now be significantly accelerated. Some officials are said to
believe
that this increase is necessary to identify 90% of all NEOs
larger than
1km across within the next ten years. Let's hope that NASA will
spent
the additional funds wisely so that this ambituous target can be
achieved.
Benny J Peiser
------------
From the NASA Office of Legislative Affairs
http://www.hq.nasa.gov/congress/
H.R.1654
National Aeronautics and Space Administration Authorization Act
of 1999
(Engrossed in House )
SEC. 103. SCIENCE, AERONAUTICS, AND TECHNOLOGY.
There are authorized to be appropriated to the
National Aeronautics and
Space Administration for Science, Aeronautics,
and Technology the
following amounts:
(1) For Space Science--
(A) for fiscal year 2000, $2,202,400,000, of which--
(i) $10,500,000 shall be for the Near Earth Object
Survey;
[...]
(B) for fiscal year 2001, $2,315,200,000, of which--
(i) $10,500,000 shall be for the Near Earth Object
Survey;
[...]
(C) for fiscal year 2002, $2,411,800,000, of which--
(i) $10,500,000 shall be for the Near Earth Object
Survey;
===================
(2) LEONID METEOR IMPACTS ON MOON CREATE CLOUD OF SODIUM GAS
From Harvey Leifert <HLeifert@agu.org>
PRESS CONFERENCE UPDATES FOR THE AGU SPRING MEETING
May 21, 1999
AGU RELEASE NO. 99-17
FOR IMMEDIATE RELEASE
Contact: Harvey Leifert
(202) 939-3212
hleifert@agu.org
Media Advisory
1999 Spring Meeting
Updated Press Conference Schedule
LEONID METEOR IMPACTS ON MOON CREATE CLOUD OF SODIUM GAS
Leonid Meteors Create a Temporary Lunar Atmosphere
June 1, 10:00 A.M. - Room 111
The November 17, 1998, return of a strong Leonid meteor shower
provided
a boost to scientists studying the origins of the Moon's weak
atmosphere. Meteor impacts on the lunar surface created a cloud
of
sodium gas that escaped from the Moon. Sodium atoms were pushed
away by
the pressure of sunlight, reaching the vicinity of the Earth on
November 19th. This cloud of lunar gas was "gravitationally
focused"
into a narrow tail that was photographed using a sensitive camera
at
the Boston University Station, McDonald Observatory, in Fort
Davis,
Texas. Experimental results and computer animations will be
presented
by researchers from the BU Center for Space Physics. (Relates to
Session P21A)
Participants:
Michael Mendillo, Professor of Astronomy, Boston University,
Boston, MA (Overview)
Steven M. Smith, Research Associate, Boston University,
Boston, MA (Observational Results)
Jody K. Wilson, Research Associate, Boston University,
Boston, MA (Computer Simulations)
For more information, please contact Harvey Leifert <HLeifert@agu.org>
===================
(3) PASEG TALK ON SPACEGUARD & THE IMPACT HAZARD
From Mark Bailey <meb@star.arm.ac.uk>
Dear Benny,
Readers of CCNet may be interested
to know that a copy of my
presentation to the All Party Parliamentary Astronomy and Space
Environment Group on 10 May is on the web, at:
http://www.arm.ac.uk/paseg/paseg.html
Best wishes,
Mark
==============
(4) SPACE ROCK HINTS AS EARLY ASTEROID FURNACE
From INSCiGHT, 20 May 1999
[http://www.academicpress.com/inscight/05201999/grapha.htm]
Thursday, 20 May 1999, 5 pm PST
Space Rock Hints at Early Asteroid
Furnace
By Erik Stokstad
Long before Earth or any other planet had formed around the sun,
a vast
cloud of dust began to coalesce into asteroids. Most of the
drifting
chunks were the kind of stone-cold rubble that Han Solo had to
weave
through in his clunky old spaceship in Star Wars, but others
oozed
lava. After a decades-long search for what melted these large
asteroids, researchers report in tomorrow's issue of Science (20
May,
p.1348) that a once-molten 4.57-billion-year-old meteorite bears
the
unmistakable signs of radioactive heat.
Planetary scientists have long suspected that the radioactive
isotope
aluminum-26 could have pumped out terrific amounts of heat in the
early
solar system. With a relatively short half-life of 730,000 years,
the
plentiful isotope could have quickly melted early asteroids. But
researchers came up empty-handed when they looked for its decay
product, magnesium-26, in meteorites from parent asteroids that
once
had molten interiors. Complicating the search, these so-called
differentiated meteorites make up fewer than 5% of those that hit
Earth.
Luckily, just such a meteorite thundered into the desert state of
Rajasthan in western India on 20 June 1996. Called Piplia Kalan
after a
nearby village, the 42-kilogram meteorite seemed a prime hunting
ground
for evidence of 26Al. The grains of the aluminum-rich mineral
plagioclase contained little magnesium, leading planetary
scientist
Gopalan Srinivasan of the Physical Research Laboratory in
Ahmedabad,
India, and his colleagues to think they had a good shot at
finding the
26Mg produced by 26Al decay. Indeed, 26Mg levels in four grains
of
Piplia Kalan were up to 3% higher than the usual amount in
terrestrial
plagioclase. By cosmic chemistry standards, says Srinivasan,
"this
excess is very significant."
The finding "strengthens implications that 26Al was the heat
source" at
the heart of asteroids, says Glenn MacPherson, a geochemist at
the
Smithsonian Institution in Washington, D.C. For connoisseurs of
asteroid history, it also suggests that the massive parent body
of
Piplia Kalan melted and cooled within 5 million years of the
solar
system's birth. This time span jibes with computer models of the
process, providing "a real shot in the arm for theoretical
work," says
geochemist Richard Carlson of the Carnegie Institution in
Washington,
D.C.
© 1999 The American Association for the Advancement of Science
[Extracted from INSCiGHT, Academic Press.]
==============
(5) RAMBLING ASTEROID TO PASS CLOSE IN '27
From San Jose Mercury News, 21 May 1999
http://www.mercurycenter.com/premium/nation/docs/asteroid21.htm
Rambling asteroid to pass close in '27
Space rock won't hit Earth, astronomers say
BY SETH BORENSTEIN
Mercury News Washington Bureau
WASHINGTON -- In the cosmic equivalent of a bullet whizzing by
Earth's ear, a half-mile-wide asteroid looks as though it will
come closer to smashing into our planet than any other space rock
astronomers have tracked.
It won't hit Earth. But its arrival in 28 years will be a visible
reminder that space can be a dangerous place.
After computing a new path for the dangerous rock, NASA
scientists
and other astronomers determined this week that the asteroid will
come close to -- but definitely not hit -- Earth on Aug. 7, 2027.
The asteroid could swing as close as 19,000 miles to Earth's
surface. That's only one-twelfth the distance between here and
the
moon.
"It is indeed very interesting," said Paul Chodas, a
research
scientist in NASA's Near Earth Object tracking office.
"We're
taking it seriously."
Because this is an asteroid that was discovered only in January,
astronomers aren't certain how close the call will be. While
19,000 miles is the closest it can come in 2027, it could miss by
as much as 600,000 miles. The most likely miss will be by a scant
32,000 miles, Chodas said.
Astronomers are certain it won't hit Earth because its current
path and the pull of gravity put it on a track that cannot
intersect with Earth's orbit, Chodas said.
But the newest tracks put the asteroid, called 1999 AN10, on top
of the list of close shaves compiled by Harvard University's
Minor
Planet Center. This rock will probably come nearly 15 times
closer
to Earth than the next known near miss, an asteroid that will
approach Earth in 2086.
If it comes as close as 19,000 or even 32,000 miles, the rock
should be visible with the naked eye, Chodas said. It would look
like a moderately bright star.
"We're not used to thinking about things being that
close," said
Clark Chapman, a planetary scientist at the Southwest Research
Institute in Colorado. "They've been coming that close for a
long
time, we just haven't known about it."
As researchers spend more time and money looking for asteroids
and
comets that come too close for comfort, there will probably be
one
or two in the next few decades that will even get closer than
1999
AN10, he said.
There is a very slight chance -- 1 in 10 million -- that when
1999
AN10 gets close to Earth in 2027, our planet's gravity will shift
the asteroid's path in such a way that it will come within 5,000
miles in 2034 and hit us in 2039, Chodas said.
But that's as likely as shooting an arrow through the keyhole of
your front door that then travels through the front-door keyhole
of
the house across the street and out through its back-door
keyhole,
said Brian Marsden, director of the Minor Planet Center.
Copyright 1999,
==============
(6) COULD ASTEROID 1999 AN10 BE USED FOR SPACE OBSERVATORY?
From Elton L. Jones <jonee@epix.net>
Dear Benny Peiser and Ron Baalke,
The purpose of this email is to pass along a concept to you and
see
what your thoughts might be on the idea of using a NEO as a
wondering
observatory.
First a little about myself. I am a subscriber to the conference
list
and have chosen so far to remain mute in that I am a only a
serious
amateur without the ability to empirically evaluate the
feasibility's
of my ideas. So if you have a isea who might like to take
this idea
and develop it, please feel free to do so. My background
professionally is that of a military weapons and training
developer. I
developed requirements documents and concept exploration
programs. As
such, I am an idea person, so-to-speak. Unable to break old
habits, I
now speak up at this stage. (Fools may tread......)
The thought which occurred to me today as I read the digest may
be
eclipsed in the impact danger debate, but do we have a
serendipity
here? Not too many years hence, does 1999 AN10 offer us a
chance for
us to instrument the asteroid and make it a long-term, distant
observatory? I could envision a battery of telescopes - optical
and
electronic, laser reflectors, laser and radar trackers to search
for
other NEOs, impact experiments, detectors of all manners. All
which we
could theoretically service on multiyear intervals. Collection
panels
could be emplaced and retrieved, supplies replenished much
as we do
Hubble or other satellites today. I am aware that we have some
plans
to land on an asteroid and return materials, but I do not
know if we
have evaluated the prospect of using a small body like this as a
spacecraft/platform.
The need for such a platform may be rendered obsolete by emerging
technology, missions already in planning, or existing approaches,
but
lets reason through this and consider what purpose a wandering
but
returning (hopefully not docking!!) platform like this might mean
for
expanded knowledge.
On the surface, potential advantages are that we could
emplace larger
payloads with less lift capacity, with less lead and transit
time.
Packages which are not feasible on the missions we are conducting
today. The approach speeds may be prohibitive. I don't even know
if
these are approaching or overtaking orbits. If not this
body perhaps
another makes more sense. Another use for AN10 could be to
experiment
with asteroid nudging technologies to assess future solutions to
eventual impact dangers but I think that may be much more
"far out".
These are just some late night thoughts - - Saturday
reading. I would
like your thoughts on the matter as to how to offer it
to
interested parties. I would hope that others out there had
had the
same idea occure to them.
I would think it too early to render a decision as to feasibility
or
even if it is at all desirable. An early thumnail oppinion
perhaps?
It might, however, be a chance to follow a process and see how
scientific communities communicate and evolve ideas given a seed
concept.
Regards,
Elton Jones
==============
(7) THE IMPACT HAZARD & SCIENCE EDUCATION FOR CHILDREN
From Malcolm Miller <stellar2@actonline.com.au>
Dear Benny,
Here is an article I have submitted as the next in my regular
series
on astronomy for THE HELIX, the Australian CSIRO's children's
science
magazine. ::::
Are we an endangered species? This has to be a
serious question,
since we now know quite well that no kind of living things can
last
for ever, even if, like the dinosaurs, they had been around for
hundreds of millions of years.
Scary stories of dangers have probably existed since
early human
ancestors avoided big carnivores on the African plains, or argued
with
cave bears for possession during the last ice age. The ice
age itself
- one of many that mark the variable climates Earth has
experienced -
was a normal extreme of temperatures that's been before and will
surely come again.
Until the nineteenth century, astronomers and
philosophers
alike believed that the planets had a lasting, even eternal
sameness.
Religious people felt that God had ordained this, and that human
beings, as the highest pinnacle of creation, had a permanent,
unchanging home. People who felt that there was evidence for
catastrophes in the distant past were laughed at; the only
catastrophe
was the Flood mentioned with the authority of the Bible.
We know now that climates change, that planetary
orbits are
chaotic, that even continents can change or vanish, that whole
ranges
of living things have vanished from the surface of the Earth in
natural processes we are only beginning to understand. And
of course
there is the possibility of an impact out of space, something
most
scientists are sure has happened many times and left its mark in
the
geological record of the rocks.
Newspapers and other media love a sensational story,
like
'Astronomers Say Asteroid Could Hit Earth', and of course most of
us
read them with interest. But behind these stories is a lot of
science,
and as well a lot of different opinions on how to deal with such
a
subject.
The classic stories of 'The Boy Who Cried Wolf' and
the caution
against calling 'Fire!' in a crowded place are examples of the
dilemma
facing scientists and the people who try to pass their
discoveries on
to non-scientists.
Crying 'Wolf!' is about the fact that when we're
warned about
something too often we begin to ignore the warning, whether it's
Mum
and Dad warning us not to ride with strangers or a
conservationist
group telling us not to cut down any more trees. The important
thing
is this: it's not just a matter of getting the facts of the
message
right, you score no points for that. No, the message must be
given in
the right way and at the right time, or people - us - will ignore
it!
When a call of 'Fire' is given in a crowded place,
people can be
killed trying to get out, whether there's a fire or not.
There's been
many an example of this in theatres, halls, and dance clubs,
especially if doors or locked or become jammed. So some people
are
quite sure that even if there IS a fire, we must keep
quiet. This is
a moral dilemma, and it has no one solution, a fact which some of
us
are very reluctant to accept.
What do you think?
What's this got to do with astronomy, you should be
asking? Just
this year, yet another NEO was discovered. NEO stands for Near
Earth
Object, and they're usually chunks of stuff less than a kilometre
across in orbits that bring them close to us at fairly regular
intervals. Obviously, if their path crosses our when we're there,
a
devastating collision would result.
Predicting the future path of these pieces is not
exact. Every time
they come close to us they can be deflected into a slightly
different
track. Should the astronomers call out to us whenever they see a
close
one? This is a serious question, and one you should debate with
your
friends. If it was going to hit us, we could do nothing about it
with
today's technology. So should the scientific community just shut
up?
Would this be censorship?
And even more scary, if we could shift it a bit so
it would be sure
to miss us this time, the effect might be to make sure it does
collide
next time it goes by, and this we can not predict. Even more
scary,
how about if there were people, say from one of those mad groups
we've
all read about, who actually wanted the Earth to be destroyed?
They
could even be pretending to deflect the object to save us but
really
have a 'hidden agenda' for disaster!
Now these might seem like wild surmises and
assumptions, but they
are real scientific problems of an ethical kind, just like ones
about
cloning humans, selling genetically altered food, burying nuclear
wastes on other people's back yards, or releasing toxic
substances
into the air and water.
They are problems that you, the citizens and
scientists of the 21st
Century, are going to have to struggle with. Maybe it's time to
start
thinking about them now.
Malcolm Miller
==============
(8) THE MOON MAKER AVAILABLE ONLINE
From Bob Kobres <bkobres@arches.uga.edu>
Hi Benny, the first two parts of The Moon Maker are available at:
http://abob.libs.uga.edu/bobk/mm/
The new compression technology used to make these images
manageable
over the Web is quite a boon! I've placed the entire 1894 study,
by
Thomas Wilson, of the swastika here:
http://abob.libs.uga.edu/bobk/sw/
Bob Kobres
==============
(9) MISSILE DEFENSE TO BE TESTED TOMORROW
From The New York Times, May 24, 1999
http://www.nytimes.com/yr/mo/day/news/national/missile-defense.html
New Anti-Missile System to be tested this Week
By WILLIAM J. BROAD
After decades of flops, $100 billion in costs and sharp rises in
the
political stakes, the Pentagon is trying again to defend the
United
States against missile attack.
The "Star Wars" dream of zapping enemy warheads with
orbiting lasers,
which President Reagan championed, is long gone. Instead, the
military
leaders of the Clinton administration have seized on an older,
less
controversial approach that is nonetheless proving to be
diabolically
hard.
On Tuesday, if all goes as planned, a launcher on a 10-wheeled
truck is
to fire a 20-foot interceptor missile from a test site in the New
Mexico desert. The goal is for the interceptor to speed above the
earth, pinpoint a mock warhead, zero in with a "kill
vehicle" on its
radiated heat and smash it to bits by force of impact.
FULL STORY at
http://www.nytimes.com/yr/mo/day/news/national/missile-defense.html
Copyright 1999, New York Times Newspapers Ltd.
==============
(10) WHIPPLE'S NEW PAPER ON COMET NUCLEI
F.L. Whipple: Note on the structure of comet nuclei. PLANETARY
AND
SPACE SCIENCE, 1999, Vol.47, No.3-4, pp.301-304
CTR ASTROPHYSICS, CAMBRIDGE, MA, 02138
The recent developments in cometary studies suggest rather low
mean
densities and weak structures for the nuclei. They appear to be
accumulations of fairly discrete units loosely bound together, as
deduced from the observations of Comet Shoemaker-Levy 9 during
its
encounter with Jupiter. The compressive strengths deduced from
comet
splitting by Opik and Sekanina are extremely low. These values
are
confirmed by theory developed here, assuming that Comet P/Holmes
had a
companion that collided with it in 1892. There follows a short
discussion that suggests that the mean densities of comets should
increase with comet dimensions. The place of origin of
short-period
comets may relate to these properties. (C) 1999 Elsevier Science
Ltd.
All rights reserved.
==============
(11) COMETARY SPLITTING DUE TO THERMAL STRESSES
L.V. Tambovtseva*) & L.I. Shestakova: Cometary splitting due
to thermal
stresses. PLANETARY AND SPACE SCIENCE, 1999, Vol.47, No.3-4,
pp.319-326
*) RUSSIAN ACADEMY OF SCIENCE,CENT ASTRON OBSERV,PULKOVSKOE
SHOSSE
65-1,ST PETERSBURG 196140,RUSSIA
We consider the thermal evolution of icy solids moving on the
highly
eccentric orbits on the base of the numerical solution of the
non-linear heat diffusion equation. Thermal stresses which arise
inside
of solids and at their surface can exceed the tidal stresses by
several
orders of magnitude in the neighborhood of the Sun and play an
important and, perhaps, a crucial role in the evolution of
comets.
A possible disintegration scenario of a distant icy solid due to
thermal stresses is presented. (C) 1999 Elsevier Science Ltd. All
rights reserved.
==================
(12) PHOTOMETRIC OBSERVATIONS OF ASTEROID 85 IO
A. Erikson*), J. Berthier, P.V. Denchev, A.W. Harris, Z. Ioannou,
A. Kryszczynska, C.I. Lagerkvist, P. Magnusson, T. Michalowski,
A. Nathues, J. Piironen, P. Pravec, L. Sarounova, F. Velichko:
Photometric observations and modelling of the asteroid 85 Io in
conjunction with data from an occultation event during the
1995-96
apparition. PLANETARY AND SPACE SCIENCE, 1999, Vol.47, No.3-4,
pp.327-330
*) DLR,INSTITUTE OF PLANETARY EXPLORATION,RUDOWER CHAUSSEE
5,D-12489
BERLIN,GERMANY
The asteroid 85 Io has been observed using CCD and photoelectric
photometry on 18 nights during its 1995-96 and 1997 apparitions.
We
present the observed lightcurves, determined colour indices and
modelling of the asteroid spin vector and shape. The colour
indices
(U-B = 0.35 +/- 0.02, B-V = 0.66 +/- 0.02, V-R = 0.34 +/- 0.02,
R-I =
0.36 0.02) are as expected for a C-type asteroid. The allowed
spin
vector solutions have the pole co-ordinates lambda(0) = 285 +/- 4
degrees, beta(0) = -52+/-9 degrees or beta(0), = 108 +/- 10
degrees,
beta(0) = -46 +/- 10 degrees and lambda(0) = 290 +/- 10 degrees,
beta(0) = - 16 +/- 10 degrees with a retrograde sense of rotation
and a
sidereal period P-sid = 0(d).286463 +/- 0(d).000001. During the
1995-96
apparition the International Occultation Time Association (IOTA)
observed an occultation event by 85 Io. The observations and
modelling
presented here were analysed together with the occultation data
to
develop improved constraints on the size of the asteroid. The
derived
value of 164 km is about 5% larger than the IRAS diameter. (C)
1999
Elsevier Science Ltd. All rights reserved.
----------------------------------------
THE CAMBRIDGE-CONFERENCE NETWORK (CCNet)
----------------------------------------
The CCNet is a scholarly electronic network. To
subscribe/unsubscribe,
please contact the moderator Benny J Peiser <b.j.peiser@livjm.ac.uk>.
Information circulated on this network is for scholarly and
educational use only. The attached information may not be copied
or
reproduced for any other purposes without prior permission of the
copyright holders. The fully indexed archive of the CCNet, from
February 1997 on, can be found at http://abob.libs.uga.edu/bobk/cccmenu.html
*
DELTA-VEE NOT DISTANCE, OR WHO SHOULD GET THE MILLION-DOLLAR
SCIENCE PRIZE?
From Duncan Steel <dis@star.arm.ac.uk>
Dear Benny,
By chance your CCNet posting on today (May 24) arrived just as I
was
sending off to John Brockman my (rather extensive) answer to a
query
he posed to the Edge members for a Million-Dollar Science Prize
(see
http://www.edge.org/).
My answer gives, inter alia, the reason why Elton Jones's
proposal
is misguided. I prefer not to say much else, although I
must state
that I find it simply unfathomable why people think that distance
rather than delta-vee is the important thing. Note that my
short
essay (appended) is not meant to be rigorous in its explanation
of
why delta-vee rather than distance is the significant factor, but
for those with little physics background it should suffice.
There
are NEOs which are excellent spacecraft targets, but not because
they
come close by the Earth: it's the low delta-vee which makes them
attractive (economical to visit)!
Cheers,
Duncan Steel
==================================================================
My nomination for the achievement which should be given the
Million Dollar
Prize is THE DISCOVERY OF THE FIRST EARTH-TROJAN ASTEROID.
And now I
explain.
There are three zones of gravitational stability relative to a
simple
(assumed isolated) planet-Sun system. These lead and lag
the planet's
orbit about the Sun by 60 degrees. In the case of Jupiter, some
hundreds of asteroids are known to inhabit these zones, called
the Trojan
asteroids. The important thing is that they have the same orbital
period
as Jupiter, and so keep in step with its circumsolar motion.
A few years back a single Mars Trojan was discovered. This
has the same
relationship with Mars.
Now we turn to the Earth. First, take a sidestep. Consider
the lunar
orbit about the Earth. The Earth-Moon pair also produces Trojan
points,
60 degrees ahead and behind the Moon's position. These are called
L4 and
L5 (technically they are often called Lagrangian points, hence
the L's;
L1, L2 and L3 are quasi-stable, and arrayed along the Earth-Moon
line).
Searches have been made for lumps of whatever at L4 and L5, using
telescopes, but nothing has been found. The reason for the
interest is
that stuff (small asteroids?) which may have found its way to L4
or L5
would be very useful for constructing/manufacturing in space,
because it
does not move relative to the Earth. Some years back an 'L5
Society' was
set up in the US, the late Gerard K. O'Neil of Princeton being a
prime
mover. The idea was to build, eventually, large space habitats at
L4/L5.
The L5 Society was later incorporated into the National Space
Society.
So far as we know, there is no usable material at L4/L5. The
reason we
would like it to be there is that no delta-vee (change in speed)
would be
required to use it there, or essentially anywhere in Earth orbit.
On the
other hand, we might hope that, like Jupiter and Mars, the Earth
might
have accumulated some solar system debris at the Trojan points of
its
orbit about the Sun.
Again, these points/zones lead and lag the planet by 60 degrees,
forming
equilateral triangles with Earth and Sun. This puts them
precisely one
astronomical unit (150 million kilometers) away from us.
Isn't that a
long way? Yes, but it's irrelevant. The essential thing in
space
economics is the delta-vee, not the distance. The reason one
needs a big
rocket to launch off the Earth is that the delta-vee is 8 km/sec
to
orbit, and 11 km/sec to escape the planet altogether. Although
the Moon
has a lower gravity, to land on the surface, and then take off
again,
requires a substantial delta-vee. The Trojan points are at
zero
delta-vee and so, even though they are a long way away, they are
more
accessible than the Moon.
If someone were to find an Earth-Trojan asteroid, then it might
well be
worth its weight in gold, quite literally, because it costs many
thousands of dollars to lift each kilogram of material off of the
Earth.
Just a rocky asteroid would be useful. A metallic one (we
know of many
elsewhere) would be great. The best would be a carbonaceous
asteroid, just
like the martian moons Phobos and Deimos, because we could
extract lots of
useful raw materials from it. (Finding a dormant cometary core -
a big lump
of ice, insulated from solar heating by a crust of rock and tar -
would be
almost too much to hope for. A source of water in space, to give
us water
itself but also oxygen, is what we really need.)
Actually we already know of several asteroids which whizz past
the Earth
with relatively low delta-vees, making them easier to get to than
the
Moon. A good example is Nereus, whose name was given after
a competition
to suggest appellations: it really is 'near us' in terms of
delta-vee.
Two spacecraft missions to Nereus are planned for 2002, the
Japanese
satellite Muses-C, and the commercial craft NEAP (Near-Earth
Asteroid
Prospector) planned by the SpaceDev corporation of San
Diego. But
finding an Earth-Trojan would be much, much better.
(In passing I note that Neil Armstrong's first words on the Moon
have
proven to be a disservice to humankind, NASA and the US
government/people, who have funded much of the space research
before and
since. Because so many wanted to see giant leaps, there
have been
multi-billion-dollar missions taking 15-20 years from planning to
completion. Much more productive would have been to
tippy-toe around the
near-Earth environs: cheaper and quicker, and more justifiable in
terms
of spin-off potential. But, hey, those photos of the outer
planets are
wonderful and inspiring.)
My nomination has a hidden agenda, now revealed. As others
have pointed
out, there are several major prizes on offer for fruitless
searches
(prove ESP etc.), although I can also think of some which were
once
*thought* impossible, but did eventuate; an example was a large
prize for
the first salmon to be caught in the River Thames, which in the
1960s was
unthinkable, but now they are common.
A *search* for an Earth-Trojan would bear fruit even if no such
object
exists, for several reasons.
First, there is a technological challenge. Astronomers normally
look out
into the night sky, mostly within 60 degrees of the opposition
point (the
point exactly opposite the Sun in the sky). An Earth-Trojan would
be
only 60 degrees away from the Sun itself. Using a ground-based
telescope
one would need to look in that direction just before sunrise and
just
after sunset (that is, similar times and locations to where Venus
and
Mercury appear). Looking along that line *many* asteroids
would be
found, mostly in the main belt. There is the problem of
differentiating
them.
Second, by looking along this direction many Earth-crossing
asteroids
(possible impactors) of the Aten type would be found, and so far
we have
discovered only a few of them (because we don't look in the right
part of
the sky).
Third, to spot moving celestial objects requires fine time
resolution,
and this is the major thing lacking in most astronomical research
(hence,
who knows what you would find?). Hermann Bondi pointed this
out back in
1970 but *still* the major emphasis is on building large
telescopes and
taking long exposures. The situation is similar to setting
up a camera
over the main concourse in Grand Central Station and taking a
24-hour
exposure. All you would see in the print would be the
building itself,
not the commuters whisking through, because they would be blurred
into
nothingness. Most astrophysical observations suffer the
same drawback,
which is all very well if you are interested in Grand Central
Station
itself and not the people who use it. Which would mean that
you'd missed
the point.
Indeed nowadays there are many amateur (not meant in a pejorative
manner,
but in its literal meaning) astronomers with telescopes and CCD
cameras
who can do what only the professionals with large instruments
could do a
few years back. Galvanizing them into action with such a
prize on offer
would produce a huge return on investment, even if (as I wrote)
the
target of the search does not exist. A professional
astronomer merely
acting as the conduit through whom all their observations were
channelled
would gain data of immense scientific import.
Like the salmon in the Thames, getting to eat the fish is all
very nice,
but irrelevant. The real outcome was that the water was
cleaned up from
its previous state as an open sewer.
For all these reasons I nominate the discovery of an Earth-Trojan
asteroid
as worthy of a Million Dollar Prize Competition.
Duncan Steel