PLEASE NOTE:


*

CCNet, 29/2000 - 8 March 2000
-----------------------------


     A Delta Air Lines jet was traversing Arizona on a clear day. The
     copilot was bombarding passengers with remarks about landmarks
     over the PA system. "Coming up on the right side of our cabin, you
     can see Meteor Crater. A major tourist attraction in northern
     Arizona, it was formed when a lump of nickel and iron weighing
     300,000 tons, 150 feet across, struck the earth at 40,000 miles an
     hour, scattering white-hot debris for miles in every direction.
     The hole measures nearly a mile across and is 570 feet deep." From
     the cabin, a passenger was heard to exclaim: "Wow! It just missed
     the highway!"


(1) FAST-SPINNING ASTEROID STUDIED
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(2) INTERESTING STRUCTURAL FEATURES ON EROS
    Ron Baalke <baalke@jpl.nasa.gov>

(3) FUTURE ESA PROJECTS
    ESA <sciweb@estec.esa.nl>

(4) RESURRECTING LIFE ON MARS?
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(5) SEARCHING FOR THE DRIVING MECHANISM BEHIND ICE AGES
    UniSci, 7 March 2000

(6) SOMETHING ELSE (NOT) TO WORRY ABOUT: VOLCANO MAY CHILL
    GLOBAL TEMPERATURES
    Space.com, 6 March 2000

(7) THE INSPIRATION OF ASTRONOMICAL PHENOMENA
    Rolf Sinclair <rolf@santafe.edu>

(8) ANCIENT ASTRONOMY AND CELESTIAL DIVINATION
    Larry Klaes <lklaes@BBN.COM>

(9) PERSPECTIVES ON THE COMET-ASTEROID-METEORITE LINK
    K. Lodders, WASHINGTON UNIVERSITY

(10) POLARISATION OF LIGHT SCATTERED BY COMETARY DUST
     A.C. Levasseur Regourd, UNIVERSITY OF PARIS

(11) DYNAMICAL LIFETIMES & FINAL FATE OF SMALL BODIES
     L. Dones et al., SW RES INSTITUTE

(12) TIDAL SPLITTING & ROTATIONAL BREAKUP OF COMETS
     B.J.R. Davidsson, UPPSALA ASTRONOMICAL OBSERVATORY


==============
(1) FAST-SPINNING ASTEROID STUDIED

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

[From Fall 1999/Number 87 issue of Lunar and Planetary Information,
http://cass.jsc.nasa.gov/publications/newsletters/lpib/lpib87/lpib87.pdf]

FAST-SPINNING ASTEROID STUDIED

Spinning faster than any object ever observed in the solar system, a
lumpy, water-rich sphere known as 1998 KY26, measuring about the
diameter of a baseball diamond, is rotating so swiftly that its day
ends almost as soon as it begins, NASA scientists report.

Asteroid 1998 KY26, where the Sun rises or sets every five minutes,
was observed June 2­8, 1998, shortly after it was discovered and as
it passed 800,000 kilometers (half a million miles) from Earth, or
about twice the distance between Earth and the Moon. Publishing their
findings in a recent issue of Science magazine, Dr. Steven J. Ostro
of NASA's Jet Propulsion Laboratory, Pasadena, California, and an
international team of astronomers used a radar telescope in
California and optical telescopes in the Czech Republic, Hawai'i,
Arizona, and California to image the 30-meter, water-rich ball as it
twirled through space. It is the smallest solar system object ever
studied in detail.

"Enormous numbers of objects this small are thought to exist very
close to Earth, but this is the first time we've been able to study
one in detail. Ironically, this asteroid is smaller than the radar
instruments we used to observe it," Ostro said.

The asteroid's rotation period was calculated at just 10.7 minutes,
compared to 24 hours for Earth and at least several hours for the
approximately 1000 asteroids measured to date. In addition, the
minerals in 1998 KY26 probably contain about a million gallons of
water, enough to fill two or three olympic-sized swimming pools,
Ostro said.

"This asteroid is quite literally an oasis for future space
explorers," he said. "Its optical and radar properties suggest a
composition like carbonaceous chondrite meteorites, which contain
complex organic compounds that have been shown to have nutrient
value. These could be used as soil to grow food for future human
outposts. And among the 25,000 or so asteroids with very reliably
known orbits, 1998 KY26 is in an orbit that makes it the most
accessible to a spacecraft."

The solar system is thought to contain about 10 million asteroids
this small in orbits that cross Earth's, and about 1 billion in the
main asteroid belt between Mars and Jupiter. However, only a few
dozen of these tiny asteroids have ever been found and, until now,
hardly anything was known about the nature of these objects.

Ostro and his colleagues used the 70-meter-diameter Goldstone,
California, antenna of NASA's Deep Space Network to transmit radar
signals continuously to the asteroid and turned a 34-meter-diameter
antenna on it to collect echoes bouncing back from the object.

1998 KY26's color and radar reflectivity showed similarities to
carbonaceous chondrites, primordial meteorites that formed during the
origin of the solar system and are unlike any rocks formed on Earth.
They contain complex organic compounds as well as 10­20% water. Some
carbonaceous chondrites contain amino acids and nucleic acids, which
are the building blocks of proteins and DNA, and hence are of interest
to scientists trying to unravel the origins of life.

A second team of astronomers used optical telescopes to track 1998
KY26, which was discovered by the University of Arizona's Spacewatch
telescope, the world's first instrument dedicated to searching for
near-Earth asteroids. Dr. Petr Pravec of the Czech Republic's Academy
of Sciences said collisions likely gave 1998 KY26 its rapid spin.

But one way or another, Pravec said, this object's 10.7-minute "day" is
the shortest of any known object in the solar system.

"The motion of the sky would be 135 times faster than it is on
Earth," he said. "Sunrises and sunsets take about two minutes on
Earth, but on 1998 KY26, they would take less than one second. You'd
see a sunrise or sunset every five minutes."

Dr. Scott Hudson of Washington State University in Pullman found the
asteroid's shape particularly surprising. Asteroids thousands of times
larger have spherical shapes as a result of their large masses and
strong gravitational fields, he said. 1998 KY26 is very unusual,
however, because gravity and mass play no significant role in its
shape. Instead, the spheroid shape is the result of collisions with
other asteroids.

===============
(2) INTERESTING STRUCTURAL FEATURES ON EROS

From Ron Baalke <baalke@jpl.nasa.gov>

NEAR image of the day for 2000 Mar 7
http://near.jhuapl.edu/iod/20000307/index.html

Interesting Structural Features on Eros

This image of the interior of Eros' saddle area, taken at a range of
204 km (127 miles), displays a paucity of craters compared to the
surface on the right hand side of the image. The saddle displays many
interesting structural features. Visible on the left wall are a
series of closely spaced grooves that follow the terrain downslope.
Opposite, on the upper right wall, trending towards the back of the
saddle is a prominent ridge. Boulders are visible throughout this
image. Features as small as 20 meters (65 feet) are discernable in this
image.
--------------------------------------------------------

NEAR image of the day for 2000 Mar 6
http://near.jhuapl.edu/iod/20000306/index.html
Large Crater on Eros

This mosaic image of the large crater at Eros' center was taken during
an optical navigation imaging sequence from a range of 127 miles (204
km). This same area was imaged following orbit insertion at a range of
approximately 210 miles (330 km) on February 14th (Feb 14 G). This
picture resolves features as small as 65 feet (20 meters) compared to
the resolution of 100 feet (30 meter) in the earlier image. The shadow
cast by the boulder near the floor of the crater (the sun is from
the northeast) is now visible. The walls of the crater display some
distinctive variations in their albedo or reflectivity. The upper part
of the walls tend to be bright, while the lower portions of the walls
and the crater floor show patches of darker or less reflective
materials. These albedo patterns are also visible on other crater
walls. To the right of the large crater two sets of closely spaced
orthogonal grooves are visible.
--------------------------------------------------------
Built and managed by The Johns Hopkins University Applied Physics
Laboratory, Laurel, Maryland, NEAR was the first spacecraft launched in
NASA's Discovery Program of low-cost, small-scale planetary missions.
See the NEAR web page at http://near.jhuapl.edu for more details.

==============
(3) FUTURE ESA PROJECTS

From ESA <sciweb@estec.esa.nl>

Six proposals, ranging from a visit to the Asteroid Belt to amazingly 
sensitive gyroscopes, will undergo close examination during the next
six months, as the European Space Agency's science advisors move
towards the selection of Flexi-missions for launch between 2005 and
2009. Science working groups and the Space Science Advisory Committee
have chosen them from 50 ideas submitted after a call for proposals
last October.

More at:
http://sci.esa.int/newsitem.cfm?TypeID=1&ContentID=9611&Storytype=7

===============
(4) RESURRECTING LIFE ON MARS?

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

[http://helix.nature.com/nsu/000309/000309-3.html]
Monday, 6 March 2000

Resurrecting life on Mars?
By PHILIP BALL

Can bacteria leave fossils? Debate on this contentious question is
central to the mystery of whether or not there is, or ever was, life on
Mars. And it is a debate that has just re-opened, thanks to a report in
the journal Earth and Planetary Science Letters[1].

In 1996, Dan Goldin, NASA's chief administrator, stunned the world by
announcing tentative evidence for life on Mars. Within the meteorite
ALH84001, found in Antarctica, David McKay of NASA's Johnson Space
Center in Houston, Texas, and his co-workers discovered what they
believed could be signatures of once-living organisms[2]. The stars of
the show, which subsequently appeared on front pages throughout the
world, were microscopic worm-like forms about 0.0001 mm (100
nanometres) long. McKay's group thought these might just be
'nanofossils' -- the fossilized remains of Martian bacteria.

Others soon disagreed. In December 1997 another team of US researchers 
found similar worm-like features in minerals examined under the
electron microscope. They showed that these to be artefacts produced by
the experimental conditions. McKay and his colleagues said that their
nanofossils looked different.

Critics also pointed out that the 'Martian nanofossils' were much
smaller than known bacteria on Earth, which are usually about five to
ten times longer. McKay's team countered that there was no reason to
assume that Martian life had to follow the same dimensions as earthly
life.

The killer blow, however, came from a workshop convened at the US
National Academy of Sciences in October 1998 to discuss just how small
a living organism can be. Participants concluded that if (as they all
assumed) life needs DNA and proteins regardless of which planet it
comes from, then there are fundamental limits to the size of bacteria.
A certain volume of cell space is required simply to get all the
necessary ingredients inside.

A cell smaller than about a million cubic nanometres -- equal to a
spherical cell about 200 nanometres across -- is simply "not compatible
with life as we know it," in the words of eminent biologist Christian
de Duve.

Now French scientists Philippe Gillet of the Ecole Normale Supérieure
in Lyon and colleagues beg to differ. Regardless of the real size limit
on living cells, they say, bacteria can leave behind mineral
'bacteriomorphs' -- fossil forms -- as small as the shapes seen by
McKay and others in meteorite ALH84001.

Gillet's group have examined fragments of the so-called Tatahouine
meteorite, named after the Tunisian village where it fell in 1931. The
fragments were collected only in 1994, after lying in the Sahara for
the intervening years. The Tatahouine meteorite is believed to be from
an asteroid.

But Gillet and his coworkers found bacteria-like forms within the
fragments, of much the same size as those seen in ALH84001. 
Cross-sections of the elongated blobs showed that they look like cells
surrounded by thick cell walls. There is no suggestion that these are
the remnants of extraterrestrials born on some asteroid. Instead, the
team believes them to be features created by terrestrial bacteria
acting on the meteorite fragments as they lay in the desert.

In support of this idea, the researchers report that they cultured
microbes from the soil surrounding the pieces of meteorite. These
bacteria have rod and oval shapes, similar to the mineral features seen
on the meteorite itself.

This suggests, the researchers claim, that such features were produced
by bacteria. Yet there is still a size discrepancy. Bacteria grown from
culture are 'normal' sized -- over a thousand nanometres long. The
'nanofossils', Gillet's team reasons, might be remnants of parts of the
bacteria or even remains of bacteria that shrunk because they were
starved of nutrients. "The size argument used against the presence of
putative life remnants in the ALH84001 meteorite is no longer valid,"
they conclude.

It is an intriguing new angle on the debate. But others will probably
still object that there is no direct evidence linking the mineral forms
with the bacteria in the soil.

[1] Gillet, P. et al. Bacteria in the Tatahouine meteorite:
nanometric-scale life in rock. Earth Planet. Sci. Lett. 175, 161-167
(2000).

[2] McKay, D.S. et al. Search for Past Life on Mars: Possible Relic
Biogenic Activity in Martian Meteorite ALH84001. Science 273, 924-930
(2000).

© Macmillan Magazines Ltd 2000 - NATURE NEWS SERVICE

=================
(5) SEARCHING FOR THE DRIVING MECHANISM BEHIND ICE AGES

From UniSci, 7 March 2000
http://unisci.com/stories/20001/0307001.htm

Driving Mechanism Behind Ice Ages Lies To The South

It seems reasonable to think that global ice ages result from climatic 
forces at work in the Northern Hemisphere. After all, that's where most
of the world's ice periodically accumulates into the massive sheets
that then grind southward over Europe, northern Asia and North America.

This intuitive assumption underlies most traditional theories for the
origin of the ice ages -- not surprising when you realize that the
ground in much of North America is still moving in response to the
weight of the last great ice sheet, which melted away more than 10,000
years ago. North is where the glacial action is. Isn't it?

Perhaps not.

New evidence based on a technical breakthrough described in the March 2
issue of Nature suggests that the real driving mechanism behind the ice
ages must lie in the tropics, or even south of the equator -- far
removed from whence the ice sheets have arrived every 100 millennia or
so for at least the past million years.

By adapting an established radiological dating technique to pinpoint
the age of a major glacial event that occurred more than 100,000 years
ago, researchers Gideon Henderson of the Lamont-Doherty Earth
Observatory and Niall Slowey of Texas A&M University have succeeded in
both bolstering the general theory of why ice ages occur, and throwing
cold water on traditional notions of how the whole thing actually
works.

FULL STORY at
http://unisci.com/stories/20001/0307001.htm

=============
(6) SOMETHING ELSE (NOT) TO WORRY ABOUT: VOLCANO MAY CHILL
    GLOBAL TEMPERATURES

From Space.com, 6 March 2000
http://www.space.com/science/planetearth/volcano_earthtemp_000306_wg.html

Volcano May Chill Global Temperatures

By Regan Morris

SINGAPORE (Reuters) - While villagers living near Mayon volcano in the
Philippines are feeling the force of brutal eruptions almost daily, the
rest of the world could feel Mayon's impact through cooler global
temperatures.

Mayon has been blasting out rock, dust and boulders as big as houses for
over a week and climate experts say if the dust makes it into the upper
atmosphere, the stratosphere, it would form a veil over the Earth,
preventing some of the sun's heat from reaching the Earth's surface and
causing temperatures to drop.

"You would expect to see a reduction in temperatures in two, three
months' time in global terms of a few tenths of a degree," said Dr Jean
Palutikof, Director of Internal Affairs of Britain's University of East
Anglia's Climate Research Unit.

"Of course, there will be regional differences with immediate effects
under the dust cloud," she told Reuters by telephone.

She said a small temperature change can have a big impact.

"It (a few tenths of a degree Celsius) sounds a small amount, but the
global warming we all worry about is about 0.7 of a degree per year,
because we're looking at global averages."

FULL STORY at
http://www.space.com/science/planetearth/volcano_earthtemp_000306_wg.html

=============
(7) THE INSPIRATION OF ASTRONOMICAL PHENOMENA

From Rolf Sinclair <rolf@santafe.edu>

THE INSPIRATION OF ASTRONOMICAL PHENOMENA -- THIRD CONFERENCE
Palermo (Sicily), Italy, December 31, 2000 -- January 6, 2001

The INSAP Conferences focus on the many and variegated cultural impacts
of the perceptions about the day- and night-time sky. They provide a
meeting place for a diverse sampling of astronomers, historians,
philosophers, and artists to meet, compare notes, and have the chance to
ask questions of one another about each other's work. The first two
meetings (Castel Gandolfo, 1994; Malta, 1999) brought together a broad
range of those working in astronomy and physics, mythology and religion,
history and the humanities, the social sciences, and art history and the
arts.

Jan. 1, 2001 is the two-hundredth anniversary of the discovery of the
first asteroid, Ceres, at the Observatory of Palermo. The centennial
year will start with the third INSAP conference. So it is particularly
appropriate that reports concerning the evidence for asteroid
impact (or more generally, impact by space rubble from any source)
on Earth be presented at this meeting.

Papers from the first meeting have been published in Leonardo and Vistas
in Astronomy, and those from the second meeting will appear shortly in
book form. A similar publication is planned for the third meeting. The
conference will be limited to about 120 attendees. Although most of the
attendees will be expected to present their original work and research
in the area of the conference, some can come as observers and will
participate fully in the meeting and the discussions. The official
language of the conference for all presented papers and discussions will
be English. The deadline date for all applications is Monday, 31 July
2000. Full information is available at

http://ethel.as.arizona.edu/~white/insap/
http://ethel.as.arizona.edu/~white/insap/

or by e-mail from
<rwhite@as.arizona.edu>,
<serio@astropa.unipa.it>, or
<rolf@santafe.edu>.

=============
(8) ANCIENT ASTRONOMY AND CELESTIAL DIVINATION

From Larry Klaes <lklaes@BBN.COM>

Ancient Astronomy and Celestial Divination
edited by N. M. Swerdlow

http://mitpress.mit.edu/promotions/books/SWEAHF99

In the ancient world, the collection and study of celestial phenomena
and the intepretation of their prophetic significance, especially as
applied to kings and nations, were closely related sciences carried
out by the same scholars. Both ancient sources and modern research
agree that astronomy and celestial divination arose in Babylon. Only
in the late nineteenth century, however, did scholars begin to
identify and decipher the original Babylonian sources, and the
process of understanding those sources has been long and difficult. 
This volume presents recent work on Babylonian celestial divination
and on the Greek inheritors of the Babylonian tradition.

6 x 9, 410 pp., 58 illus., cloth ISBN 0-262-19422-8
Dibner Institute Studies in the History of Science and Technology

===========
(9) PERSPECTIVES ON THE COMET-ASTEROID-METEORITE LINK

K. Lodders*) & R. Osborne: Perspectives on the comet-asteroid-meteorite
link. SPACE SCIENCE REVIEWS, 1999, Vol.90, No.1-2, pp.289-297
     
*) WASHINGTON UNIVERSITY,DEPT EARTH & PLANETARY SCI,PLANETARY  
   CHEM LAB,CAMPUS BOX 1169,ST LOUIS,MO,63130

We discuss the possibility that CI and CM carbonaceous chondrites are
fragments of extinct cometary nuclei. Theoretical and observational
work suggests that comets evolve into asteroids, and several extinct
cometary nuclei are now suspected to he among the near Earth object
population. This population is the most likely source of meteorites and
consequently, we may expect that some meteorites are from extinct
comets in this population. The mineralogy and chemistry of CI and CM
chondrites is consistent with the view that they originate from
asteroidal objects of carbonaceous spectral classes, and these objects
in turn may have a cometary origin. We do not suggest that CI or CM
chondrites are directly delivered by active comets during perihelion
passage or that these chondrites come from cometary debris in meteor
streams. Instead, we summarize arguments suggesting that CI and CM
chondrites represent fragments of cometary nuclei which evolved
into near Earth asteroids after losing their volatiles. Copyright 2000,
Institute for Scientific Information Inc.

=================
(10) POLARISATION OF LIGHT SCATTERED BY COMETARY DUST

A.C. Levasseur Regourd: Polarization of light scattered by cometary
dust particles: Observations and tentative interpretations. SPACE
SCIENCE REVIEWS, 1999, Vol.90, No.1-2, pp.163-168

*) UNIVERSITY OF PARIS 06,BP 3,F-91371 VERRIERES BUISSON,FRANCE

Analysis of the polarization of light scattered by cometary particles
reveals similarities amongst the phase curves. together with some clear
differences: i) comets with a strong silicate emission feature present
a high maximum in polarization, ii) the polarization is always slightly
lower than the average in inner comae and stronger in jet-like
structures. These results are in excellent agreement with the Greenberg
model of dust particles built up of fluffy aggregates of much smaller
grains. Also, they suggest the existence of different regions of
formation, and of different stages of evolution for the scattering
particles inside a given cometary coma. Copyright 2000, Institute for
Scientific Information Inc.

=================
(11) DYNAMICAL LIFETIMES & FINAL FATE OF SMALL BODIES

L. Dones*), B. Gladman, H.J. Melosh, W.B. Tonks, H.F. Levison,
M. Duncan: Dynamical lifetimes and final fates of small bodies: Orbit
integrations vs Opik calculations. ICARUS, 1999, Vol.142, No.2,
pp.509-524

*) SW RES INST,SPACE STUDIES DEPT,1050 WALNUT ST,SUITE
   426,BOULDER,CO,80302

The dynamical lifetimes of small bodies against ejection from the
Solar System or collision with the Sun or a planet are often
estimated by Monte Carlo codes based on the equations of Opik and
using a method implemented by Arnold. Such algorithms assume that
orbital changes are dominated by close encounters, and that
successive encounters are uncorrelated, We have compared the results
of an Opik code (H. J. Melosh and W. B, Tonks, Meteoritics 28, 398
(1993)) and a fast integrator (H, F. Levison and M, J, Duncan, Icarus
108, 18 (1994)) to investigate the regimes of validity of the
Opik-Arnold approach, We investigate the transfer of ecliptic comets
from Neptune-crossing orbits to observable Jupiter-family comets, the
dynamics of Halley-type comets, and the transport of meteorites among
the terrestrial planets, In all cases, the Opik code overestimates
the median lifetime of the small bodies, although both codes show a
rapid initial loss of objects followed by a slow decay, For martian
impact ejecta, some of which find their way to Earth as the SNC
meteorites, the Opik code substantially overestimates lifetimes
because of its neglect of secular resonances, which rapidly pump
eccentricities (B, J, Gladman ed at, Science 271, 1387 (1996)). (C)
1999 Academic Press.

============
(12) TIDAL SPLITTING & ROTATIONAL BREAKUP OF COMETS

B.J.R. Davidsson: Tidal splitting and rotational breakup of solid
spheres. ICARUS, 1999, Vol.142, No.2, pp.525-535
     
*) UPPSALA ASTRONOMICAL OBSERVATORY,BOX 515,S-75120 UPPSALA,SWEDEN

A number of new expressions for the Roche limit are derived in order
to investigate the splitting behavior of cometary nuclei when passing
close to massive bodies. These expressions handle both tensile and
shear failure, taking the radius, density, material strength,
rotation period, and spin axis orientation of the body into account.
The critical period for which bodies in free space disrupt due to the
centrifugal force is also investigated, resulting in functions
depending on radius, density, and material strength. (C) 1999
Academic Press.

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