PLEASE NOTE:


*

CCNet DIGEST, 1 October 1998
----------------------------------------------

(1) TREMENDOUS GAMMA-RAY FLARE BLASTS EARTH
      NASANews@hq.nasa.gov

(2) SPACE ELEVATOR
      Scott Manley <spm@star.arm.ac.uk>

(3) METEORITE PICTURE?
      Paolo Farinella <paolof@keplero.dm.unipi.it>

(4) FIRST GRADUATE PROGRAMME IN ASTROBIOLOGY
      Andrew Yee <ayee@nova.astro.utoronto.ca>

(5) ASTEROID 4 VESTA
     A. Ghosh & H.Y. McSween, UNIVERSITY OF TENNESSEE

(6) THE CHANGING SPECTRUM OF VESTA
       A.L. Cochran*) & F. Vilas, UNIVERSITY OF TEXAS

(7) ANALYSING CENTAURS
     J.K. Davies et al., JOINT ASTRONOMY CTR

(8) COMETARY SODIUM IN HALE-BOPP
      M.E. Brown et al., CALTECH

(9) THE DEATH OF COMET TABUR 1996 Q1
      M. Fulle et al., ASTRONOMICAL OBSERVATORY TRIESTE

(10) RADAR DETECTABILITY OF A SUBSURFACE OCEAN ON EUROPA
        C.F. Chyba*), S.J. Ostro, B.C. Edwards, SETI INSTITUTE

(11) DYNAMICS OF COSMIC DUST NEAR THE SUN
        A. Krivov et al., MAX PLANCK INSTITUTE

(12) SIZE & ORBIT DEPENDENT TRENDS IN THE REFLECTANCE COLORS OF
        EARTH-APPROACHING ASTEROIDS
        D.L. Rabinowitz, CALTECH, JET PROP LAB

=========================
(1) TREMENDOUS GAMMA-RAY FLARE BLASTS EARTH

From NASANews@hq.nasa.gov

Donald Savage
Headquarters, Washington, DC                       Sept. 29, 1998
(Phone:  202/358-1547)

Tim Tyson
Marshall Space Flight Center, Huntsville, AL
(Phone:  256/544-0994)

RELEASE:  98-172

TREMENDOUS GAMMA-RAY FLARE BLASTS EARTH


An intense wave of gamma rays, emanating from a catastrophic
magnetic flare on a mysterious star 20,000 light years away,
struck the Earth's atmosphere on August 27, 1998, providing
important clues about some of the most unusual stars in the
Universe.  Scientists said the gamma radiation posed no health
risk to humans.

     The wave hit the night side of the Earth and ionized (or
knocked electrons out of) the atoms in the upper atmosphere to a
level usually seen only during daytime.  This astonishing blast of
ionization was detected by Prof. Umran Inan of Stanford
University.  "It is extremely rare for an event occurring outside
the solar system to have any measurable effect on the Earth," Inan
said.  It was so powerful that it blasted sensitive detectors to
maximum or off-scale on at least seven scientific spacecraft in
Earth orbit and around the solar system. 

       The wave of radiation emanated from a newly discovered type
of star called a magnetar.  Magnetars are dense balls of super-
heavy matter, no larger than a city but weighing more than the
Sun.  They have the greatest magnetic field known in the Universe,
so intense that it powers a steady glow of X-rays from the star's
surface, often punctuated by brief, intense gamma-ray flashes, and
occasionally by cataclysmic flares like the one observed on August
27.  Astronomers think that all these effects are caused by an
out-of-control magnetic field -- a field capable of heating,
mixing, and sometimes cracking the star's rigid surface to bits.

       In June a team of scientists led by Dr. Chryssa Kouveliotou
of NASA's Marshall Space Flight Center in Huntsville, AL, used
NASA's Compton Gamma Ray Observatory to detect a series of about
50 flashes from the star, a type called a Soft Gamma Repeater
(SGR), known as "SGR1900+14" in the constellation Aquila.  During
the flashing episode, Kouveliotou's team, in collaboration with
Dr. Tod Strohmayer and his colleagues at NASA's Goddard Space
Flight Center, Greenbelt, MD, pointed sensitive X-ray detectors
aboard NASA's Rossi X-ray Timing Explorer satellite toward the
star.  They found faint X-rays coming from the star, which pulsed
regularly in intensity every 5.16 seconds. 

    These 5.16-second pulses already had been detected in April,
when Dr. Kevin Hurley, University of California, Berkeley, aimed
the Japanese/NASA Advanced Satellite for Cosmology and
Astrophysics (ASCA) at the star.  Comparisons of the ASCA and RXTE
data showed that the X-ray pulses were gradually slowing down.

       The finding implies that the Soft Gamma Repeater has a
magnetic field about 800 trillion times stronger than Earth's
magnetic field, and about 100 times stronger than any found
anywhere in the Universe.  Kouveliotou and her team had earlier
found that another SGR was also a magnetar.  This was exactly what
Dr. Robert Duncan, University of Texas, Austin, and Dr.
Christopher Thompson, University of North Carolina, Chapel Hill,
predicted in 1992 when they originated the "magnetar" theory.

       Before the NASA team could announce these conclusions,
SGR1900+14 emitted the tremendous flare of August 27, which was
observed by almost every spacecraft with a high-energy radiation
detector in space. 

       "Magnetars seem to answer several mysteries about the
structure and evolution of stars," said Kouveliotou. "We think
magnetars spend their first 10,000 years as Soft Gamma Repeaters. 
As they weaken with age and slow their rotation, they become
Anomalous X-ray Pulsars -- stars that do not have enough 'juice'
to flash anymore, but which emit a steady flow of X-rays for
perhaps another 30,000 years.  After that, they fade to black and
drift for eternity through the heavens.  The absence of observable
pulsars in some supernova remnants just means that the pulsar's
lights have gone out sooner than we expected."

       A magnetar forms from the explosion, or supernova, of a
very large, ordinary star.  The star's heavy center collapses
under its own gravity into a dense ball of super-compressed matter
12 miles across.  This "neutron star" consists mostly of neutrons
in a dense fluid, but the outer layers solidify into a rigid crust
of atoms about 1 mile deep, with a surface of iron.

       Even with this solid crust, a magnetar is incredibly
unstable.  Almost unimaginable magnetic fields, about 800 trillion
times that of Earth's, cause the crust to crack and ripple in
powerful starquakes.  The energy released in these explosive
starquakes streams out into space as intense flashes of gamma-
rays.  In the August 27 flare, pure magnetic energy was also
released, as the star's entire crust was broken to bits.

       "A magnet this strong could erase the magnetic strip on the
credit cards in your wallet or pull the keys out of your pocket
from a distance halfway to the Moon," said Duncan.

========================
(2) SPACE ELEVATOR

From Scott Manley <spm@star.arm.ac.uk>

> I think it is time NOW to consider WHICH asteroid to use for a future
> space elevator. Once the job is under way I guess it's too late to
> reconsider. Even with the best of techniques it's bound to be fraught
> with danger to extend a base by 'docking' another asteroid to it.

There are plenty of candidates out there.

If we are to Follow Sir Arthur's suggestion of carbon Nanotubes as an ideal
candidate for constructing an orbital tower then we can estimate just how
large an asteroid is needed. I don't have the precise strength to mass ratio
of carbon nanotube cables (if anyone has this and other physical data please
tell me and I'll do this by more than dead reckoning) but some guesstimation
for a tower capable of supporting a few million tons of tension would require
a cable massing several million tons. If you have some magical machine capable
of processing raw asteroid material and weaving the carbon into perfect
nanotube cables then you can make do with an asteroid a few hundred metres
across - with all the unused materials being used as the counterweight.

Such a machine would have it's work cut out -  growing cables which are metres
across at very high speeds - if you wanted to build a 100,000km tower in a
year you'd need to produce the cable at about 10 miles per hour, 24 hours a
day.

Then we have a minor problem with rotation, the completed structure must
rotate at the same speed as earth, and the cable is by no means rigid. As the
cable is extended if the parent body is rotating then the tendency is for the
cable to begin to spiral round as the moment of inertia of the whole system
changes. OTOH  how do you go about spinning up a 100,000 kilometer cable - I'd
guess that the space engineering techniques required for this are somewhat
more sophisticated than those required to park a small asteroid in earth orbit.

It may one day be done - in fact the only reason I can see for not creating
something like this would be if some radical new method of space launching
became possible (e.g. good old sci-fi antigravity).

Think Big!

Scott Manley (aka Szyzyg)

=====================
(3) METEORITE PICTURE?

From Paolo Farinella <paolof@keplero.dm.unipi.it>

I have recently visited the Melk Monastery, not far from Vienna, which has been
completely restored some a few years ago and is now a magnificent (mainly early
XVIII century) complex of buildings, overtowering the village and the Danube. In
the small museum inside the Monastery there are several XV century paintings,
including one on the martyrdom of St. Catherine by a painter called Hans Egkel.
Now, the painting shows a strange scene, with a kind of dark opening in the sky
from which angels throw many stones toward the ground, aiming (I suppose) at the
evil characters who are putting the Saint to death. Now, the museum catalogue gives
`um 1470' for the painting's date, but I don't know which uncertainty does `um'
imply. Might it be possible that the painting was done after the 1492 Ensisheim
fall, given the wide circulation of the news about it in central Europe (see the
beautiful article by Marvin 1992, "Meteoritics" 27, 28-72)? Or that is there some
other connection to real meteorite falls?  Please send me any information or
suggestion on this matter at:  paolof@dm.unipi.it

                                   Paolo Farinella

=========================
(4) FIRST GRADUATE PROGRAMME IN ASTROBIOLOGY

From Andrew Yee <ayee@nova.astro.utoronto.ca>

University of Washington

FROM: Vince Stricherz, 206-935-7430, vinces@u.washington.edu

Contacts:

James Staley: (206) 543-0461 or (206) 543-6646 or e-mail at
jstaley@u.washington.edu.

Woodruff Sullivan: (206) 543-7773 or (206) 543-2888 or e-mail at
woody@astro.washington.edu.

Conway Leovy: (206) 543-4952 or e-mail at leovy@atmos.washington.edu.

Richard Gammon: (206) 543-1609 or (206) 543-4301 or e-mail at
gammon@u.washington.edu.


UW prepares for first graduate program in astrobiology to train those who
will hunt for life in outer space

The University of Washington is poised to become the first institution
anywhere to launch a doctoral program specifically geared to train
scientists to search for life on celestial bodies such as Mars or Europa,
an icy moon of Jupiter.

The astrobiology program will be financed by a 5-year, $2 million grant
announced today by the National Science Foundation and supplemented by
$500,000 from the university.

The highly interdisciplinary curriculum will involve 11 UW degree programs --
Oceanography, Astronomy, Aeronautics & Astronautics, Genetics, Chemistry,
Biochemistry, Microbiology, Atmospheric Sciences, Geophysics, Geological
Sciences and History. Graduates can receive degrees in any of those areas,
with an endorsement noting an emphasis in astrobiology.

The School of Oceanography will provide dedicated laboratory space for
students to study organisms that live in extreme conditions. Oceanography
professors John Delaney and Jody Deming and associate professor John Baross
have closely studied organisms living in high-temperature, high-pressure
conditions in ocean environments where little light penetrates. Baross is
trying to relate the conditions in which those organisms live now to
conditions when life began on Earth 3.5 billion years ago.

Two entities outside the university also are participating. The Pacific
Northwest National Laboratory in Richland will offer students a chance to
study microbial life in the subterranean basalt formations in Eastern
Washington. ZymoGenetics Inc. of Seattle, a subsidiary of Novo Nordisk A/S
of Denmark that is interested in enzymes from unusual bacteria, is offering
summer internships so students can pursue that work.

"We recognize that there is a good possibility that life exists in the solar
system outside Earth, but if that life does exist it would be microbial, not
the higher forms," said James Staley, a UW microbiology professor who is the
principal investigator for astrobiology.

Likely sites for such life are Mars, where there is evidence of water, or
the ice-clad moon Europa.. The key to finding life in such forbidding
environments is understanding how life exists in extreme conditions on Earth
-- such as hot springs in Yellowstone National Park, undersea vents where no
sunlight penetrates and temperatures reach several hundred degrees, pools of
brine within polar sea ice, and volcanic basalt formations.

"We have microbial systems on Earth that are good models for those on Mars
or Europa, and those systems are poorly studied," Staley said. He added that
such life forms were the precursor to advanced life on Earth, so their
presence on other planets could signal the eventual evolution of advanced
life there, as well.

The idea for an astrobiology program grew out of a special seminar, Planets
and Life, offered at the university in 1996 shortly after the discovery of
planets orbiting nearby stars and an announcement that NASA scientists
possibly had found microbial fossils inside a Martian rock. That claim since
has drawn much scientific skepticism, but the success of the seminar -- it
was attended by 30 graduate students and 20 post-doctoral researchers and
faculty, and it sparked much campus excitement -- laid a foundation for a
program in astrobiology.

Woodruff Sullivan, a UW astronomy professor and adjunct history professor,
spearheaded the seminar and is an astrobiology co-investigator. He expects
about a dozen students when the program begins in the fall quarter of 1999.

But there is much to be done before then. Five new courses must be designed
to complement existing courses that will be included in the curriculum,
Sullivan said. Departments involved will have to devise different ways of
testing and grading students involved in astrobiology, since an astrobiology
student pursuing a degree in astronomy, for instance, will have
significantly different course demands than other astronomy students.
One-third of astrobiology course work will be in areas not closely related
to the student's home department, so an astronomy astrobiology student might
spend a great deal of time studying microbiology.

Students also must take part in an annual workshop, three days of work in
the field. It could be looking for microbes at the Hanford Nuclear
Reservation, Sullivan said, or using an electron microscope to study comet
dust. "Everyone will have to get their hands dirty."

Conway Leovy, a UW atmospheric sciences professor and also a co-investigator,
expects the program to be an education for faculty members as well as
students. But he said the students will be particularly challenged as they
blaze a new path, and it will be some time before the first doctoral degrees
in astrobiology are awarded.

"Astrobiology students will have to learn rigorously as well as more broadly
than most other science graduate students," Leovy said. "We probably can't
expect to see the fruits of our efforts in the form of many Ph. D. graduates
sooner than five years from now."

Richard Gammon, who is a UW chemistry and oceanography professor and also is
an adjunct professor of atmospheric sciences, helped write a financing
proposal for the astrobiology degree program. He believes the approach of
breaching traditional barriers between different science disciplines was a
key to National Science Foundation support.

"All of these efforts are to meet the needs of students of the future, who
are going to need training across fields," Gammon said.

The UW is one of 17 universities sharing in $40.5 million in National
Science Foundation graduate education and research training grants. For more
information about the NSF program, visit http://www.nsf.gov/igert/ on the
World Wide Web.

================
(5) ASTEROID 4 VESTA

A. Ghosh & H.Y. McSween:  A thermal model for the differentiation of Asteroid 4
Vesta, based on radiogenic heating. ICARUS, 1998, Vol.134, No.2, pp.187-206

UNIVERSITY OF TENNESSEE, DEPT GEOL SCI, KNOXVILLE, TN, 37996

A finite element code has been developed to model the thermal history of Asteroid 4
Vesta. This is the first attempt to model the thermal history of a differentiated
asteroid through core and crust formation and subsequent cooling until geochemical
closure is attained. The results of the simulation are consistent with
chronological measurements and other constraints provided by cumulate and
noncumulate eucrites believed to have been derived from Vesta. The work solves two
major problems with the hypothesis of heating by decay of Al-26, an extinct
radionuclide, postulated to be a plausible heat source in the early Solar System.
First, the model demonstrates that it is possible to keep the mantle of Vesta hot
for similar to 100 Ma, thereby explaining the observed difference in ages
between cumulate and noncumulate eucrites. Second, the simulation offers a possible
explanation of why detectable excesses of Mg-26 (the decay product of Al-26) are
not observed in noncumulate eucrites. The simulation draws a model
chronology of Vesta and predicts times (relative to CAI formation) for accretion at
2.85 Myr, core formation at 4.58 Myr, crust formation at 4.58 Myr, and geochemical
closure at similar to 100 Myr for a H-chondrite asteroidal bulk composition. Decay
of Fe-60 is found to cause no perceptible difference in the thermal history of
Vesta, even when sequestered into a central core. Although chondritic xenoliths
have not been described in HED igneous lithologies, the thermal model suggests the
possibility that a veneer of unmelted near-surface material should remain. (C) 1998
Academic Press.

==================
(6) THE CHANGING SPECTRUM OF VESTA

A.L. Cochran*) & F. Vilas: The changing spectrum of Vesta: Rotationally resolved
spectroscopy of pyroxene on the surface. ICARUS, 1998, Vol.134, No.2, pp.207-212

*) UNIVERSITY OF TEXAS, AUSTIN,TX,78712

Moderate spectral resolution observations of the 505-nm Fe2+ pyroxene feature in
the reflectance spectrum of Vesta were acquired across the complete surface of the
asteroid. The feature is consistently centered at 506.54 nm, suggesting an augite
(high-calcium) composition. Variations in the equivalent width of the feature
correlate with topographically high terrain on Vesta's surface, and could be due to
the presence of another material (possibly olivine), or particle size variations,
or both. (C) 1998 Academic Press.

==================
(7) ANALYSING CENTAURS

J.K. Davies*), N. McBride, S.L. Ellison, S.F. Green, D.R. Ballantyne: Visible and
infrared photometry of six Centaurs. ICARUS, 1998, Vol.134, No.2, pp.213-227

*) JOINT ASTRONOMY CTR, 660 N AOHOKU PL, HILO, HI, 96720

We present infrared (JHK) and visible (VRI) observations of the Centaurs 2060
Chiron, 5145 Pholus, 7066 Nessus, 1995 DW2, 1995 GO, and 1997 CU26. These are
combined whenever possible to derive relative reflectance spectra between 0.55 acid
2.2 mu m. The extreme visible to infrared color of Pholus found in 1992
is confirmed, as is the redness of 7066 Nessus, We refine the rotation period and
lightcurve of 1995 GO and resolve ambiguous determinations of its V-R color. We
find that 1997 CU26 has V-JHK colors very similar to 1995 GO. Our data imply
changes in the visible-IR color of 2060 Chiron with level of cometary
activity and, aware of the difficulties of combining nonsimultaneous data, we
comment on the likely reality of these. We find a wide range of reflectances within
the Centaur population with no obvious correlations with heliocentric distance. (C)
1998 Academic Press.

=================
(8) COMETARY SODIUM IN HALE-BOPP

M.E. Brown*), A.Z. Bouchez, H. Spinrad, A. Misch: Sodium velocities and sources in
Hale-Bopp. ICARUS, 1998, Vol.134, No.2, pp.228-234

*) CALTECH, DIV GEOL & PLANETARY SCI, PASADENA, CA, 91125

We use spatially resolved high-resolution spectra of the 5890 and 5896 Angstrom
sodium D lines in the nuclear regions of Comet Hale-Bopp to determine the sources
of cometary sodium. Comparison of the data to a Monte Carlo model of sodium
dynamics suggests that the intensities and velocities of sodium in HaleBopp can be
explained if 55% of the observed sodium is produced at the nucleus, the remaining
45% is produced in an extended source, and the sodium is accelerated by solar
radiation pressure. Observations of H2O+ in Hale-Bopp and subsequent modeling of a
plasma-derived sodium source show that this source produces sodium at higher
velocities than those observed; any contribution from such a source must be small.
The combined nucleus and extended sources of sodium which fit our data best would
create a sodium tail at a scale 100 times larger than that of these observations
identical in morphology and velocity to that observed in Hale-Bopp. (C) 1998
Academic Press.

===============
(9) THE DEATH OF COMET TABUR 1996 Q1

M. Fulle*), H. Mikuz, M. Nonino, S. Bosio: The death of comet tabur 1996 Q1: The
tail without the comet. ICARUS, 1998, Vol.134, No.2, pp.235-248

*) ASTRONOMICAL OBSERVATORY TRIESTE, VIA TIEPOLO 11, I-34131 TRIESTE, ITALY

After a normal brightness increase, Comet Tabur 1996 Q1 showed a remarkable
photometric behavior by rapidly fading in late October 1996. In this paper we
analyze three CCD images of the remnant dust tail observed during the fading of the
comet around perihelion and model them by means of the inverse dust tail model (M.
Fulle, 1989, Astron. Astrophys. 217, 283-297). Assuming hemispherical sunward dust
emission from the nucleus, satisfactory fits of the observed tail brightness
distribution, turning axis and temporal fading allow us to conclude that only dust
was observed, and contamination by gas and/or ions in the images is negligible. The
model results include the temporal variation of the dust ejection velocity, the
size distribution and dust mass loss rate. These values show a strong correlation
during fading with strong drops consistent with the comet's deactivation. In
particular, the slow increase of the dust mass loss rate in September and its low
absolute values allow us to exclude outbursts preceding fading and to exclude that
the disappearance was due to a complete nucleus disruption. In this case, the
nucleus mean radius should have been no more than 350 m (for a nucleus bulk density
of 100 kg m(-3)), which seems inconsistent with the observed water loss rate. A
probable explanation of the comet fading is that the comet nucleus deactivation was
due either to seasonal effects, putting all active areas in permanently night
sides, or to the complete end of the whole nucleus surface activity (possibly due
either to nucleus mantling or to the end of the ice reservoirs). (C) 1998 Academic
Press.

==================
(10) RADAR DETECTABILITY OF A SUBSURFACE OCEAN ON EUROPA

C.F. Chyba*), S.J. Ostro, B.C. Edwards: Radar detectability of a subsurface ocean
on Europa. ICARUS, 1998, Vol.134, No.2, pp.292-302

*) SETI INST, 2035 LANDINGS DR, MT VIEW, CA, 94043

A spacecraft in orbit around Jupiter's moon Europa can use ice penetrating radar to
probe for a possible liquid water ocean beneath Europe's surface ice and to
characterize other important subsurface structure. Consideration of available
constraints on the properties of Europa's ice, possible subsurface temperature
gradients, and possible impurities in the ice places an upper limit of about 10 km
on the depth to which an ocean might be detectable with an orbiting radar. (C)
1998 Academic Press.

=================
(11) DYNAMICS OF COSMIC DUST NEAR THE SUN

A. Krivov*), H. Kimura, I. Mann: Dynamics of dust near the sun. ICARUS, 1998,
Vol.134, No.2, pp.311-327

*) MAX PLANCK INST AERON,KATLENBURG DUHM,GERMANY

In an effort to shed some light on the main features of the innermost part of the
zodiacal cloud, the solar F-corona region, for which both observational and
theoretical studies still give controversial results, we model the dynamics and
physical evolution of dust grains at several solar radii (Ro) from the Sun. We take
into account solar gravity, direct solar radiation pressure, Poynting-Robertson
force, sublimation, and the Lorentz force. The latter is computed on the base of
(i) the grain surface potentials derived from elaborate model calculations and
shown to vary from +3 to +12 V; (ii) a multipole radial model of the actual solar
magnetic field for the period 1976-1996. The dust particles are assumed to be
porous and compact spherical grains, made of two types of material: dielectric
(silicate) grains and absorbing (carbon) ones. Our main results can be summarized
as follows. The decrease of grains' sizes and the dynamics of particles in the
orbital plane are well described by taking into account solar gravity and radiative
forces together with the sublimation process, being relatively insensitive to the
electromagnetic force. The silicate grains typically move inward in near-circular
spirals until intensive sublimation starts and they disappear at heliocentric
distances from 2 to 3 R.. The carbon grains intensively sublimate near 4R.. After
several radial oscillations, they are eventually ejected out as beta-meteoroids,
when they approach a critical radius of approximate to 2.4 mu m (for porous grains)
or approximate to 0.5 mu m (for solid spheres), which corresponds to the radiation
pressure to solar gravity ratio beta equal to unity. The orientation of the orbital
planes of the particles is dictated by the Lorentz force. Both porous and compact
carbon grains possess high beta ratios and must be larger than respectively 2.4 and
0.5 mu m to reach the near-solar region. For these sizes, the Lorentz force is
relatively weak, comes basically from the dipole zonal component of the field, and
leads to low-amplitude oscillations of orbital inclinations and a precession of the
lines of nodes. The same behavior is predicted for silicate porous (compact)
grains larger than 2 mu m (1 mu m) and 1 mu m (0.5 mu m) for the periods of quiet
and active Sun, respectively. From these sizes to smaller ones, the Lorentz force
effectively broadens the initial distribution of inclinations of silicate grains.
Submicrometer-sized particles easily get in polar and retrograde orbits well before
the evaporation. On the whole, we find that the dynamics of near-solar grains
depend radically on their sizes, chemical composition, and structure and, in cases
of relatively small dielectric grains, may be severely correlated to the solar
activity cycle. (C) 1998 Academic Press.

===================
(12) SIZE & ORBIT DEPENDENT TRENDS IN THE REFLECTANCE COLORS OF
        EARTH-APPROACHING ASTEROIDS

D.L. Rabinowitz: Size and orbit dependent trends in the reflectance colors of
earth-approaching asteroids. ICARUS, 1998, Vol.134, No.2, pp.342-346

CALTECH, JET PROP LAB, 4800 OAK GROVE DR, PASADENA, CA, 91109

New observations show that reflectance colors of Earth-approaching asteroids depend
on their sizes and orbits. Most bodies larger than similar to 2 lan have reddish
colors similar to common main-belt asteroids of spectral type S. Smaller
bodies, and those that may have recently migrated from the main belt, have
relatively neutral spectra in the 0.5- to 0.8-mu m wavelength range, These trends
may result from the action of ''space-weathering,'' recently proposed to explain
similar spectral variations on the surfaces of S-type asteroids and the disparity
between the colors of ordinary chondrite meteorites and their probable main-belt
parents. (C) 1998 Academic Press.

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CCNet DEBATE, 1 October 1998
------------------------------------------------

SUPPOSE THEY HAD A MEDIA OPPORTUNITY AND NO ONE SHOWED UP;
THE DEEP SPACE 1 BRIEFING;
NEWT SMELLS BLOOD, BEGINS ATTACK ON NASA

From E.P. Grondine <epgrondine@hotmail.com>

Benny -

I went up to Washington last Tuesday to attend the briefing on
Deep Space 1.  My day actually started the night before, as I
gathered together some of my late mother's papers for the family
accountant, and I started my day Tuesday with a visit to his office.

This matter delayed my arrival at the day's first NASA event, which
was the donation by Dan Goldin of used computers from NASA to Kramer
Junior High School.  Kramer Junior High School is in Anacostia,
one of the "bad sections of town", and I really have to give Goldin
credit for being one of the few federal officials with guts enough to go
there.  When I arrived he was posing for a photo with the best
students, and he was really enjoying it, and the kids were too.
It's sad no one saw it, as none of the mass media came out to the
presentation.  Everyone seemed to be completely devoting their entire
resources to the Tripp Affair.

I struck up a conversation with one Thomas Gore, who has been
working for years to keep area kids in the system.  We reflected on how
crack cocaine had devasted the neighborhood, and the sight of the
boarded up houses across from Kramer made me shudder.  It was not
how I remembered it; by the way, did I mention that I attended
Kramer Junior High?

Of course, while the neighborhood was a little rough then, it was
nowhere near the state it is in today, and Mr. Gore and I reflected that
it had been the crack cocaine, starting about 1983-1984, that had caused
the real decline.  I also spoke with the principle of Kramer, who was
bitter that while the Republican Congressmen and Starr would spend $40
million investigating the President, they would not spend 4 dollars on
her kids. 

I wouldn't normally bring this up. but I just want to put the Deep
Space 1 funding numbers in a little perspective.  Of course, when the
next big one comes the folks in Anacostia will be just as dead as
the rest of us, unless we take steps now, so here goes...

The total cost of Deep Space 1 is estimated at $152.3 million
dollars.  Of this $94.8 million dollars went to pre-launch
development, $43.5 million dollars for launch on a Boeing Delta II
launcher, $10.3 million dollars will go for mission operations, and
$3.7 million dollars for science.  The Delta II is also going to be used
to place in orbit a student Earth resources satellite, whose images will
be delivered free daily over the internet, and which also has an amateur
radio transponder, so NASA is really going to be getting a lot out of
this one rocket launch.

What are the key points of Deep Space 1 in terms of planetary
defense?  First, DS-1 is going to test a new optical system capable both
of navigating it to asteroid 1992 KD (discovered by Eleanor Helin -
congratulations Eleanor), as well as controling it during its fly-by. 
During the flight the optical system will calculate DS-1's position by
examining which stars are obscured by the 250 asteroids in its
computer's database.  As it approaches 1992 KD the same system will
build a model of 1992 KD by combining images of the rotating asteroid;
during fly-by it will take action by comparing information from its CCDs
with the stored model.  Pretty impressive stuff if it works!

This optical navigation system did not come from the military, but
was developed by JPL itself.  But it is heartening to note that there
was co-operation between the military and JPL in the development of the
probe, as BMDO contributed solar panels for DS-1, and the Air Force's
Phillips Laboratory contributed the probe's multifunctional structure. 
So the technology tested will definetly be available for use for
planetary defense when it is needed.

Relative speed at closest encounter with 1992 KD is estimated at 15
kilometers per second, and the science array will be active for
around 1,000 seconds either side of this, for a total time of around
2,000 seconds.  The same camera that is used for navigation will then be
taking multi-spectral images, and DS-1 is also equipped with 
ultra-violet and infra-red spectrometers.  These should return
excellent data on 1992 KD's composition, which is so important in
figueing out how to stop these things.  As a bonus, it is hoped that
DS-1 will then be able to continue on and get similar data from both
asteroid Wilson-Herrington (suspected to be a comet transitioning to an
asteroid) and Comet Borrelly.

I'm sorry I did not get this to the Conference earlier, but
Thursday Republican leader (and $4 million dollar friend of Rupert
Murdoch) Newt Gingrich began his attack on NASA.  Due to the collapse of
Russia's economy Russia had been having trouble meeting its commitments
for the International Space Station, and Newt had been sending out his
colleagues to test the waters as to whether this could be used to launch
an attack on President Clinton, and to further weaken Clinton by taking
away this important tie to Russia.

The trigger for Newt's attack was news that has been trickling out
of NASA that the director of the Russian Space Agency, Yuri Koptev, had
promised to give Kazakhstan $115 million dollars a year for the use of
the Baykonur launch facility, and now Koptev was trying to get this
money from NASA to pay them.

Newt's attack was so out of touch with reality that it is difficult
to describe it, but I'll try.  Newt accused NASA of slowing down the US
space program, and claimed that over the last 30 years the US would have
settled the Moon if NASA had just not gotten in the way.
Newt called the International Space Station an absolute disaster, which
he blamed entirely on Clinton.

Now I'm sure that everybody on this list is perfectly aware that
Earth impactors are not going to be found and stopped by private
efforts.  Maybe some of the more delusional space fantasists, think
this, but I'm sure that no one on this list shares in their insanity. 
We all know that NASA is essential if we are going to have a planetary
defense.

So what I'd like everyone on the list to consider what they can do
to stop Newt now, and to stop him cold, before he can do any more
damage.  The way I see it, the first step in planetary defense is no
longer getting NASA to devote more resources to the problem, but instead
to preserve NASA itself.

                                             Best wishes -
                                                  Ed



CCCMENU CCC for 1998

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