CCNet, 28 October 1999


     "The biological puzzle of snowball Earth is very interesting. Events
     suggest that life was more robust than we thought and that the Earth's
     climate was much less stable than we assumed."
            -- James F. Kasting, professor of geosciences and meteorology

      Syuzo Isobe <>

     Ron Baalke <>

     Andrew Yee <>

     Andrew Yee <>

     Andrew Yee <>


      UniSci, 26 October 1999


From Syuzo Isobe <>

Syuzo ISOBE, National Astronomical Observatory, Mitaka, Tokyo, Japan
and Japan Spaceguard Association


The Japanese Spaceguard Association, set up in October 1996, has made
proposals to address the NEO hazard.  In addition to activities
including public lectures and the publication of our newsletter, we try
to raise the support of the government and private organizations to
build ground-based, and also space-based and lunar-based, telescopes. 
Two ground-based telescopes started to be built in January 1999, and
will be in operation in 2000. Proposals for lunar-based and space-based
NEO missions are under discussion within NASDA, Japan. In this paper,
we discuss the ideas relevant to the various stages in our proposed

It is clear that a near-earth object (NEO) hit the Earth at a point
presently appearing at Yucatan Peninsula, Mexico, 65 million years ago
and that nearly all the dinosaurs were killed by this strike. The
degree of destruction is strongly dependent on the mass of an impacting
object, or equivalently on its diameter. The 1992 Spaceguard report
edited by Morrison showed that an object with a diameter larger than
0.5 km is able to destroy nearly all human development and that only a
small fraction of people in the world can survive. A collision of an
NEO with a diameter smaller than 500 m produces only a local
catastrophe, but the probability of such an event is much higher than
that of a globally catastrophic event.

Certainly, we have to work hard to prevent such a collision, but it is
inevitably necessary to detect and track all NEOs in order to be 100%
certain of escaping a collision. However, the number and brightness of
NEOs depend on the diameters, and it is very hard to detect all the
small NEOs. Figure 1 shows the numbers of NEOs with large and small
diameters as a function of aphelion distance.  Since a certain fraction
of NEOs have aphelion distances larger than 2.5 AU, we need to observe
down to 21st magnitude for the NEOs with a diameter larger than 0.5 km.
From previous observations and research, the total number of those NEOs
is estimated to be around 2,000 to 10,000.

Detection of objects with brightness of 21st magnitude can be pursued
by ground-based telescopes, but needs 10 to 20 years given 10-20 NEO
detection telescopes of 1 m class. However, if one tries to detect NEOs
with small diameter, one wants space-based and/or lunar-based
telescopes, and since the number of NEOs in this category is so large,
it would take a very long time to detect all the NEOs even if multiple
telescopes are launched.

There is a further consideration relating to NEO impacts. Before the
desired level of completeness in NEO detection has been achieved, there
is a significant possibility that the Earth will have been hit by NEOs
approaching from around the solar direction (Isobe and Yoshikawa 1996,
Asher, Yoshikawa, and Isobe 1999). Isobe and Yoshikawa found that the
percentage of this type of close approach to the Earth is much higher
than would result from a uniform distribution of approach directions. 
This type of NEO impact has in principle no warning time.

Figure 1. Distribution of apocentric distances for near-earth asteroids
with known orbits.

Considering the above discussion, three categories of observations are
necessary as shown in table 1.

Table 1. Methods suitable for detecting various classes of near-earth

Our knowledge of the NEO problem was much smaller when a working group
on NEOs was set up within the IAU in 1991. This was just around the
time when the significance of the Chicxulub crater was recognized.  It
has a diameter of 180 km and was produced 65 million years ago, clearly
being associated with the extinction of the dinosaurs.  We set up an
NEO study-group in Japan, in 1993, and held an international conference
on the Hirayama Families of asteroids.  Following the start of the
Spaceguard Foundation in March, 1996, we set up the Japan Spaceguard
Association in October, 1996.

We visited different funding organizations to make them aware of the
proposals shown in table 1. Fortunately, we succeeded in getting a
budget for 1998 to 2001 from the Science and Technology Agency to build
a 1.0 m detection telescope and a 0.5 m follow-up telescope (Figure 2).
As Yoshikawa (1999) showed, if we are able to determine exact orbital
elements, we can determine when an object approaches the Earth. 
Fortunately, no NEO on a collision course has been detected, although
such NEOs as 1997 XF11 and 1999 AN10 show close approaches to the Earth
within 30 to 50 years. After completing our telescopes, we shall have a
capability to detect NEOs matching the LINEAR telescope of the US Air
Force in New Mexico. However, the number of telescopes to detect NEOs
is not enough and we need more than 100 years may be needed to detect
all the NEOs with diameter larger than 500 m. More than 10 high quality
telescopes are necessary to make this time duration short.

Figure 2. Spaceguard observation facilities under construction(September 29,
Until we detect all the NEOs there is always a possibility for an
asteroid coming from the blind (near-solar) direction to collide with
the Earth. This gives no warning time. Therefore, to give a certain
length of warning time, we are proposing a lunar-based or space-based
small telescope which searches continuously areas surrounding the solar

For NEOs with a diameter between 50-500 m we need to observe down to
27th magnitude, for which either 8 m class ground-based telescopes or
1-2 m class space-based or lunar-based telescopes are necessary. 
Considering all the NEOs we are proposing the strategy shown in table 2
to avoid not only the extinction of humans but also the total
destruction of a country. We would like to detect all the NEOs before a
collision occurs.

Table 2. A strategy to detect the near-earth asteroids.

There is much debate as to how to publicize a calculated collision
probability of a given asteroid at its discovery. At this stage there
is a background collision probability of 10^-6 event/year for an
asteroid producing global damage. In the case of 1999 AN10 the
collision probability varied between 10^-4 - 10^-6 event/year as new
observational data were progressively added. However, the Japan
Spaceguard Association claims that since the collision probability is
so small, since a much more accurate collision probability will be
available after follow-up observations within a few years, and since we
have a fairly long warning time, we should not publicize the
information. If this kind of information is publicized repeatedly, it
would result in accusations of crying wolf and the public would not
believe astronomers working on the NEO problem.

Table 3. Necessary mass of colliding satellite to change an asteroid
orbit to its collision course.

There are some proposals to prevent an NEO collision with short warning
time. One should be careful on this point. If the warning time is
short, we need much energy to mitigate the NEO. As an indication table
3 shows the necessary mass of a space satellite to deflect an NEO from
a colliding orbit, for different warning times. Since this mass is very
large for the case of an asteroid with a diameter larger than 500 m,
there is practically no way to mitigate an asteroid collision except
using many space nuclear weapons. The Japan Spaceguard Association does
not take this option, because we need much money to maintain such
nuclear shield systems and we may not use this system since the
collision probability is once in a hundred thousand years. There
remains a danger in keeping nuclear weapons which may also used for

A perfect Spaceguard system can be set up with a cost less than
that to maintain a nuclear space shield system for one year.  When we
detect all the NEOs and determine those orbits, we can estimate the
time of an asteroid collision well in advance. If we find an NEO
colliding with the Earth within 10 years, we should suffer a global
catastrophe, since that probability is far below that for your car
accident (which is said once one hundredth per person per his hundred
year lifetime). Following the above discussion, the Japan Spaceguard
Association is proposing the strategy to detect NEOs as shown in table


Asher, D. J., Yoshikawa, M. and Isobe, S. 1999, Asteroid Collision
   Frequencies and Directions for the Terrestrial Planets, ICARUS, submitted.
Isobe, S. and Yoshikawa, M. 1996, Asteroids Approaching the Earth from
   Directions around the Sun, Earth, Moon, and Planets, Volume 72, pp263-266.
Yoshikawa, M. 1999, private communication.

For further informations icluding its figures and tables can be seen in
Isobe's web page which will be open
on December 1, 1999.


From Ron Baalke <>

Leonids In The Crystal Ball
Marshall Space Flight Center

Most experts agree that 1999 is a likely year for a Leonids meteor storm.

October 27, 1999: Imagine tuning in to the local TV weather report and
hearing this from the weatherman:

"Good evening space weather lovers! Last night Earth was hit by a
high-pressure solar wind stream. It's expected to persist for 3 or 4 more
days producing a 50% chance of mid-latitude aurora. But the big news today
is the 1999 Leonid meteor shower. Experts are predicting a big storm on
November 18th with up to 100,000 shooting stars per hour. Of course, we
could be off by a couple of years. The storm might hit in 2001 instead. Or
maybe not at all! Hey, if predicting these things were easy we wouldn't need

One day, space weather forecasts like this could be commonplace. As our
society comes to rely on satellites, cell phones, and other space-age
gadgets, forecasting solar storms and meteor showers can be just as
important as knowing the chances of rain tomorrow. Three weeks from now we
may be treated to a very visible reminder of space weather when the Leonid
meteor shower strikes on November 18, 1999.

What's the probability of significant meteoroid precipitation? That's what
stargazers and satellite operators everywhere would love to know.

Most experts would agree that predicting the Leonids can be tricky. To
understand why it's helpful to know the difference between a "meteor shower"
and a "meteor storm." Simply put, meteor showers are small and meteor storms
are big. Meteor showers produce a few to a few hundred shooting stars per
hour. Meteor storms produce a few thousand to a few hundred thousand meteors
per hour. A meteor storm, like a total solar eclipse, ranks as one of
Nature's rarest and most beautiful wonders.

A Leonid meteor shower happens every year around November 17 when Earth
passes close to the orbit of comet Tempel-Tuttle. Usually not much happens.
The Earth plows through a diffuse cloud of old comet dust that shares
Tempel-Tuttle's orbit, and the debris burns up harmlessly in Earth's
atmosphere. A typical Leonid meteor shower consists of a meager 10 to 20
shooting stars per hour.

Every 33 years something special happens. Comet Tempel-Tuttle swings through
the inner solar system and brings a dense cloud of debris with it. For 3 or
4 years after its passage the Leonids can be very active. In 1966 for
instance, over 100,000 meteors per hour were seen from parts of North
America. Curiously, there isn't a full-fledged storm every time
Tempel-Tuttle passes by. Sometimes there's simply a stronger-than-average
shower. Sometimes nothing happens at all!

Will there be a storm in 1999? (Probably, yes.)

Tempel-Tuttle visited the inner solar system most recently in late 1997 and
early 1998. The subsequent Leonids display, in Nov. 1998, was marvelous as
observers all over the world were treated to a dazzling display of fireballs
(shooting stars with magnitudes brighter than -3). Nevertheless, the 1998
Leonids were a shower, not a storm. The maximum rate of meteors last year
was about 250 per hour. Scientists have learned that if Earth crosses the
orbit of Tempel-Tuttle too soon after the comets passage, then there is no
storm, just a strong shower. Apparently that's what happened in 1998. In
recent history no Leonid storm has ever occurred less than 300 days after
Tempel-Tuttle passed by Earth's orbit. In 1998, Earth followed the comet to
the orbit-crossing point by only 257 days.

The period of maximum activity during the 1998 Leonid shower took place
about 12 hours before the earth crossed Tempel-Tuttle's orbital plane. The
early activity caught many observers by surprise, but it was business as
usual for the unpredictable Leonids. Rainer Arlt of the International Meteor
Organization noted that while the maximum activity came early, there was a
secondary maximum when the Earth passed the comet's orbit. This
pattern is similar to that observed in 1965, the year that preceded the
great Leonids storm of 1966. In his report, Bulletin 13 of the International
Leonid Watch: The 1998 Leonid Meteor Shower, Arlt wrote:

     [T]he radar, visual, and photographic records of the 1965 Leonids
     indicate an activity profile which resembles that of the 1998
     Leonids. Even the low population index seems comparable. Judging
     from these phenomenological facts, we may expect 1999 to show a
     similar shape of activity as in 1966. The actual maximum meteor
     numbers are hardly predictable.

If the 1999 Leonids are anything like the 1966 storm, stargazers are
definitely in for a treat. The 1966 event was, predictably, somewhat
unexpected. The comet had passed by Earth's orbit in 1965, so astronomers
were aware that something might happen. But, judging by the paucity of the
1899 and 1932 showers, it was widely thought that the orbit of the debris
stream had been deflected so much by gravitational encounters with other
planets (mainly Jupiter) that a close encounter with Earth's orbit was no
longer possible. The best predictions suggested a strong shower over Western
Europe with 100 or so meteors per hour.

Instead, there was an stunning display of shooting stars over western North
America. This recollection by James Young at JPL's Table Mountain
Observatory in California gives a sense of what the storm was like:

     "This very noteworthy [1966] meteor shower was nearly missed
     altogether... There were 2-5 meteors seen every second as we
     scrambled to set up the only two cameras we had, as no real
     preparations had been made for any observations or photography.
     The shower was expected to occur over the European continent.

     The shower peaked around 4 a.m., with some 50 meteors falling per
     second. We all felt like we needed to put on 'hard hats'! The sky
     was absolutely full of meteors...a sight never imagined ... and
     never seen since! To further understand the sheer intensity of
     this event, we blinked our eyes open for the same time we normally
     blink them closed, and saw the entire sky full of streaks ...

The 1966 return of the Leonids was one of the greatest displays in history,
with a maximum rate of 2400 meteors per minute or 144,000 per hour.

Joe Rao, a Leonids expert who lectures at New York's Hayden Planetarium,
also advocates 1999 as possibly the best year for a storm during this 33
year cycle. Writing for Sky &Telescope he says:

     Based on what happened last November, I will venture a prediction.
     If a meteor storm is to take place at all, 1999 would appear to be
     the most likely year for it to happen. But even if this year's
     Leonids are richer in number, observers should not expect the same
     high proportion of fireballs that were seen in 1998. Instead, a
     more even mix of bright and faint meteors is likely. [ref]

Rao bases his argument on historical precedent and the Earth-comet geometry.
During the seven most recent Leonid storms when Earth crossed
Tempel-Tuttle's orbit soon after the comet, the average distance between the
comet and Earth was 0.0068 astronomical unit. The average number of days
between the comet's passage and the Earth's arrival at the plane of the
comet's orbit was 602.8 days. With the 1999 values of 0.0080 AU and 622.5
days, Rao says we ought to be in a prime position to see significant, if not
storm-level, activity.

Rao is also a meteorologist for News 12 Westchester, which seems a suitable
occupation for predicting meteor showers.

In 1999, the Earth will pass nearly three times as far from the comet's
orbital path as it did in 1966 and more than six times farther than it did
during the great storm of 1833. If the peak of the Leonids arrives exactly
when the Earth passes through the comet's orbital plane, Donald Yeomans of
JPL gives 01:48 UT on November 18, 1999 as the most likely time for the 1999
maximum [ref]. That would make Europe and West Africa the best places to
watch the show. However, Leonid meteor showers frequently arrive much
earlier or later than predicted, so any place on the globe could be favored.

If the peak of the Leonids occurs over Europe or the Atlantic Ocean, then
observers in the USA could be in for an unusual treat. The Leonid radiant
would just be rising over North America at the time. In the eastern US sky
watchers would see a large number of earth-grazing meteors skimming
horizontally through the upper atmosphere. "Earth grazers" are typically
long and dramatic, streaking far across the sky.

To look or not to look, that is the question

     All sorts of conjectures were made by all sorts of people ... We
     may learn of this that, when men are in a high state of
     excitement, their testimony must be taken with many grains of
               From a first-hand account of the 1833 Leonid Meteor
     Shower. by Elder Samuel Rogers

Most experts agree that 1999 is the most likely year for a Leonids meteor
storm during the current 33 year cycle. However, if 1999 turns out to be a
disappointment, don't despair! There are other studies that suggest 2000,
2001 or even 2002 could be better years. The Leonids are simply hard to

If 1999 is the year, when should you look? Most experts predict that the
Leonids peak will occur between 0100 and 0400 Universal Time on November
18th. However, it is important to remember that such predictions are always
uncertain. The 1998 Leonid fireball display occurred nearly 16 hours before
the predicted maximum! No matter where on Earth you live, the morning of
November 18 will probably be the best time to look for Leonids in 1999. This
is true even if morning where you live occurs much earlier or later than
0100-0400 UT.

Conventional wisdom says that meteor observing is always best between
midnight and dawn local time on the date of the shower (November 18 in this
case). For a shower or storm like the Leonids that might be relatively
brief, it is best to start watching no later than midnight. In fact, when
the author of this story went outside last year at midnight to view the 1998
Leonids, the shower was already well underway! With this in mind you may
decide it's a good idea to begin observing even earlier, say, 10 p.m. on
November 17.

In the coming weeks Science@NASA will post more stories about the Leonids
with observing tips for meteor watching with the naked eye, video cameras
and other types of recording devices. One thing seems sure, no matter where
you live: The Leonids are coming and, on Nov 18, 1999 the place to be is
outside, looking up!


From Andrew Yee <>

Pennsylvania State University

A'ndrea Elyse Messer, (814) 865-9481 (o),
Vicki Fong, (814) 865-9481 (o),

Embargoed For Release: October 27, 1999 p.m.

Oxygen May Be Cause of First Snowball Earth

Denver, Colo. -- Increasing amounts of oxygen in the atmosphere could
have triggered the first of three past episodes when the Earth became
a giant snowball, covered from pole to pole by ice and frozen oceans,
according to a Penn State researcher.

"We have convincing evidence that at least six of the seven
continents were once glaciated, and we also have evidence that some
of these continents were near the equator when they were covered with
ice," says Dr. James F. Kasting, professor of geosciences and
meteorology. "Two of these global glaciations occurred at 600 and 750
million years ago, but the earliest occurred at 2.3 billion years

According to Kasting, if it is assumed that the magnetic evidence for
glaciation at the equator is correct, then only two possible
explanations for equatorial glaciation exist.

One is that the Earth's tilt, which is now at 23.5 degrees from
vertical, was higher than about 54 degrees from vertical. This would
have positioned Earth so that the poles received the most solar
energy and the equator would receive the least, creating a glacier
around the middle but still leaving the poles unfrozen.

The other possibility, which is the one that Kasting leans toward
now, is that the greenhouse gases in the atmosphere fell low enough
so that over millions of years, glaciers gradually encroached from
the poles to 30 degrees from the equator. Then, in about 1,000 years,
the remainder of the Earth rapidly froze due to the great
reflectivity of the already ice-covered areas and their inability to
capture heat from the sun. The entire Earth became a snowball with
oceans frozen to more than a half mile deep.

"For the latest two glaciations, carbon dioxide levels fell low
enough to begin the glaciation process. However, for the earliest
glaciation, the key may have been methane," Kasting told attendees at
the annual meeting of the Geological Society of America today (Oct.
27) in Denver.

"The earliest known snowball Earth occurred around the time that
oxygen levels in the atmosphere began to rise," says Kasting, who is
a member of the Penn State Astrobiology Center. "Before then, methane
was a major greenhouse gas in the atmosphere in addition to carbon
dioxide and water vapor."

As oxygen levels increased, methane levels decreased dramatically and
carbon dioxide levels had not built up enough to compensate, allowing
the Earth to cool. Oxygen levels need only reach a hundredth of a
percent of present-day oxygen levels to convert the methane
atmosphere completely. Once the Earth is snow covered, it takes 5 to
10 million years for the natural activity of volcanoes to increase
carbon dioxide enough to melt the glaciers.

Regardless of the greenhouse gas involved, the pattern of freezing
and defrosting would be the same. Because the sun has been constantly
increasing in brightness, it would take more greenhouse gas in the
past to compensate for the fainter sun. For the glaciations at 600
and 750 million years ago, estimates are that carbon dioxide levels
equal to recent pre-industrial levels or up to three times
pre-industrial levels would have been sufficient for snowball Earth
to occur.

Because many continents existed in the warm equatorial areas during
the most recent glaciations, Kasting believes that rapid weathering
of calcium and magnesium silicate rocks, which consumes carbon
dioxide, lowered levels sufficient to cool things.

"It would have taken nearly 300 times present levels of carbon
dioxide to bring the Earth out of its ice cover," says Kasting.
"Then, once the high reflectivity ice was gone, the carbon dioxide
would have overcompensated and the Earth would become very warm until
rapid weathering would remove carbon dioxide from the atmosphere."

One reason that many scientists initially rejected the snowball Earth
theory was that biological evidence does not suggest that the various
forms of life on Earth branched out from the latest total glaciation.
A variety of life forms had to survive from before the glaciation,
which is difficult to imagine on an ice-covered world. Perhaps the
ancestors of life today survived in refuges like hot springs or near
undersea thermal vents.

"The biological puzzle of snowball Earth is very interesting," says
Kasting. "Events suggest that life was more robust than we thought
and that the Earth's climate was much less stable than we assumed."

EDITORS: Dr. Kasting is at (814) 865 - 3207 or at by email.


From Andrew Yee <>


Tuesday, October 26, 1999

Mystery Follows Meteors
By John Fleck, Albuquerque Journal Staff Writer

Astronomers chasing rare and mysterious "glowworms in the sky" that
swarm every 33 years or so will converge on Albuquerque next month.

The occasion is the annual Leonid meteor shower, an every-November
light show in the night sky that once every 33 years turns into an
extravaganza of shooting stars.

This year's show is expected to be a doozy.

That's a problem for satellite operators, a treat for stargazers and
a potential scientific bonanza for Air Force astronomer Jack Drummond
and his colleagues.

They're trying to understand how little grains of dust and sand
slamming into Earth's atmosphere can leave twisting, billowing,
glowing trails that sometimes last for hours.

The trails, which Drummond calls "glowworms in the sky," were first
noticed in 1833, but they've never been explained, Drummond said.

Last year, the scientists used a modest Leonid show to study a
handful of glowworms, armed with a telescope and lasers at an Air
Force observatory on a hilltop south of Albuquerque.

This year they'll be back in force, using a suite of special
instruments to try to pin down the cause of the strange glowing

The Leonids occur when Earth, on its orbit around the sun, passes
through the trail of dust left by a comet called Tempel-Tuttle, which
orbits the sun every 33 years.

The trail is always there, which is why we get Leonids every November.

But in 1998, Tempel-Tuttle passed near us, leaving a load of fresh
dust, which is why scientists expect a light show this year.

"Ninety-nine's the big year. I'm willing to make small bets -- not
big bets, but small bets," said Kevin McKeown, an Albuquerque amateur
astronomer and veteran meteor-watcher.

The storm of shooting stars is caused when grains of dust and sand
collide with Earth's atmosphere, explained Sandia National
Laboratories physicist Dave Crawford.

They might not be big, but their speed as they slam into Earth's
atmosphere is prodigious -- about 40 miles per second.

That pumps enough energy into the atmosphere to heat it so much that
electrons are stripped off of its molecules, creating the brief flash
of a meteor.

"That's really what you're seeing is glowing air," Crawford said.

But in some cases, there's more.

Some of the brightest meteors leave a more lasting luminous trail,
and therein lies the mystery Drummond and his colleagues are trying
to solve.

Drummond's "glowworms in the sky" were first recorded during a Leonid
shower in 1833, the scientist told reporters during a briefing

According to McKeown, they are visible in other meteor showers but
most common during the especially bright and spectacular Leonids.

At their best, he said, they are "very easy naked-eye objects,"
requiring no telescope or binoculars to see.

Drummond and his colleagues used the Air Force's Starfire Optical
Range telescope on a Kirtland Air Force Base hilltop to study them
during last November's Leonid shower.

They shone a laser at it hoping to see the light reflected back. When
it wasn't, they knew the glowworm wasn't a smoky trail.

Instead, something in the trail itself, 50 miles high in the thinnest
part of the atmosphere, is generating its own light. But what?

This year, they aim to find out.

Three instruments called spectrographs, which split light into its
various colors, will be used.

Because different chemicals emit different colors of light, a
spectrograph can be used to determine the glowworms' chemical

The scientists will be training their instruments on the sky shortly
after midnight on the mornings of Nov. 17 through 19, hunting

And for members of the general public, it's also worth staying up
late, said McKeown. A dark spot out of town is best, but the Leonids
are likely to be bright enough that even in the glare of city lights
they should put on a show.

"You've got to go out and look," he said. "If you miss it, you'll
never be able to live with yourself."

Copyright © 1999 Albuquerque Journal

[NOTE: Images from the Starfire Optical Range experiment are
available at - A.Y.]


From Andrew Yee <>

ESA Science News

26 Oct 1999

Earth's 'Second Moon' in a 'ménage à trois'

We will never see it but the Earth has at least one other natural
satellite. In discovering several new types of orbital motion, a team
of British scientists has shown that the gravitational forces of our
planet and of the Sun allow our planet to capture passing asteroids.
One of them is named 'Cruithne', and can be considered -- at least
for the next 5000 years -- as 'Earth's second Moon'.

The work of coorbital dynamics by a team from Queen Mary and
Westfield College in London was published 27 September in the US
publication 'Physical Review Letters'. Fathi Namouni, Apostolos
Christou and Carl Murray have taken even further the discoveries of
Joseph-Louis Lagrange.

The 18th century French mathematician gave his name to the five
special points of equilibrium between the gravitational forces of a
planet like our Earth and those of the Sun. The 'Lagrangian points'
-- also known as libration points -- demonstrate the so-called
'three-body problem' when a planet and its Sun can catch a third
companion (see diagram).

The first point L1 is situated on a line between the planet and its
Sun. SOHO, the ESA-NASA Solar and Heliospheric Observatory is the
first spacecraft to exploit such a position. It is currently orbiting
the inner L1 position 1.5 million km from Earth using this vantage
point to study the Sun. L2 is on the same line but on the outer side
from Earth.

The L3 point is precisely on the other side of the Sun. L4 and L5 are
at the summit of two equilateral triangles with a common base being
the line between the Earth and the Sun. Joseph-Louis Lagrange had
already shown that objects turning around L4 and L5 could easily stay
there. This configuration applies to other planets of the solar
system. Indeed Jupiter has hundreds of Trojan asteroids and Mars has
at least two. Although Saturn itself has none, its own moons Tethys
and Dione maintain Trojan asteroid satellites at Lagrangian points.

The orbits of these third bodies are exotic. The Trojan asteroids
describe a 'tadpole-shaped' pattern around the L4 and L5 points. Even
more peculiar is the 'horseshoe orbit' in which the third body turns
around the three points of equilibrium, L3, L4 and L5.

Cruithne is such an object. Discovered in 1997, it is a 5-km diameter
asteroid that takes 770 years to complete its horseshoe orbit. Thus
every 385 years it comes to its closest point to Earth, some 15
million kilometres. Last time was in 1900, next -- if you can wait --
will be in 2285.

The British team integrated Cruithne's parameters into their
mathematical models, deducing that it can remain in its present state
for 5,000 years before leaving. They have even calculated that
'Earth's second moon' is likely to be a second-comer having been
trapped in a similar orbit some time in the past 100,000 years.
"Cruithne is a case example, proof that our work is not just abstract
calculations," says Carl Murray. "The mathematical model that we have
developed has been able, not only to predict several new types of
previously unsuspected motion, but has it has subsequently been
confirmed by investigating numerically the orbits of real solar
system objects. Nature has already provided examples of every kind
of orbit that the theory can provide."

Examining existing catalogues of near-Earth objects to see whether
there were any other similar cases, the Queen Mary and Westfield
College team have discovered four: three concerning Earth and one for

The main significance of the work is that it provides a complete
classification of coorbital motions. It could lead to a greater
understanding of other asteroids, including their likelihood of
hitting Earth and of how the planets were formed. Space mission
planners could devise new gravitational tricks for their space
probes. Murray himself is one of the European members of the Imaging
Science Subsystem team on the Cassini orbiter part of the
Cassini-Huygens mission.

The team also shows that the forces of attraction in the three-body
problem are also present in other domains of science -- such as
chemistry where, for instance, two electrons of an atom of helium
display a similar 'ménage à trois' around their nucleus.


* Physical Review Letters abstract
* More about SOHO
* More about Huygens
* The Lagrange points (NASA webpage)

[NOTE: Illustrations supporting this release are available at ]


G. Camardi: Charles Lyell and the uniformity principle. BIOLOGY &
PHILOSOPHY, 1999, Vol.14, No.4, pp.537-560


The theoretical system Lyell presented in 1830 was composed of three
requirements or principles: 1) the Uniformity Principle which states
that past geological events must be explained by the same causes now in
operation; 2) the Uniformity of Rate Principle which states that
geological laws operate with the same force as at present; 3) the
Steady-state Principle which states that the earth does not undergo any
directional change. The three principles form a single thesis called
'uniformitarianism' which has been repeatedly questioned and which has
been reputed to be unable to face the competing 'directional synthesis'
based on the theory of the earth's cooling down. As a result, the
significance of Lyell's system has been reduced to a simple 'actualism'
which admits the validity of the only Uniformity Principle. I believe
that the only way to understand Lyell's role in the history of science
is to maintain the unity of his synthesis. To show the Newtonian roots
of this synthesis I will compare Lyell's principles and Newton's Rules
of Reasoning. I will conclude with an analysis of the methodological
function of principles in Lyell's scientific endeavour. Copyright 1999,
Institute for Scientific Information Inc.


From UniSci, 26 October 1999

It appears that Neanderthals coexisted with early modern humans in
central Europe for thousands of years -- and very likely mated with
them -- according to new radiocarbon dating by an international team of
scientists. They documented the fact that Neanderthals roamed central
Europe as recently as 28,000 years ago, the latest date ever recorded
for Neanderthal fossils worldwide.

The announcement was made jointly today by Washington University in St.
Louis and Northern Illinois University.

The team's findings -- published in today's issue of the Proceedings of
the National Academy of Sciences -- may force other scientists to
rethink theories of Neanderthal extinction, intelligence -- and
contributions to the human gene pool.

The research on Neanderthal fossils from the Vindija cave site in
Croatia also casts doubt on the theory that the Iberian Peninsula was
the Neanderthals' last stand.

"Most scientists would have expected to find the latest Neanderthal in
southwest Europe rather than in central Europe," said paleontologist
Fred H. Smith, a research team member and chairman of the Anthropology
Department at Northern Illinois University. "The new radiocarbon dates
suggest Neanderthals would have coexisted with early modern humans in
central Europe for several millennia."

"The extinction of the Neanderthals by early modern humans, whether by
displacement or population absorption, was a slow and geographically
mosaic process," said team member Erik Trinkaus, an anthropologist at
Washington University in St. Louis. "The differences between the two
groups in basic behavior and abilities must have been small and rather

Using direct accelerator mass spectrometry radiocarbon dating, team
member Paul Pettitt and colleagues at Oxford University in England
determined that two pieces of Neanderthal skulls from the Vindija cave
site are between 28,000 and 29,000 years old. These new Croatian dates
refute previous evidence indicating central European Neanderthals had
disappeared as early as 34,000 years ago.

Neanderthals are commonly portrayed as prehistoric humans of limited
capabilities who were rapidly replaced and driven to extinction by
superior early modern humans, once the modern humans appeared in

Scientists surmised that modern humans from the Near East moved first
into central Europe and then into western Europe, pushing Neanderthals
into the Iberian Peninsula, at the extreme southwest portion of the
continent, where the Neanderthals died off about 30,000 years ago.

Coupled with his earlier work at Vindija, Smith said the new
radiocarbon dates call into question this pattern of Neanderthal
migration and extinction. In his earlier work, Smith also argued that
late Neanderthal fossils from the cave site had some modern human
anatomical characteristics.

The Croatian dates indicating thousands of years of coexistence between
Neanderthals and early modern humans in central Europe forces a new
interpretation of a study in which scientists compared the DNA of a
Neanderthal with the DNA of contemporary humans. Published two years
ago, the study concluded that, while Neanderthals and early modern
humans may have coexisted in Europe, they probably didn't mate.

"The new dates, in my opinion, add some support to the idea that there
was probably a good deal of genetic exchange between Neanderthals and
modern humans," Smith said. "When you look at the anatomy of early
modern Europeans, you also find a number of features that are hard to
explain unless you allow the Neanderthals some ancestral status. And
actually, the Neanderthal mitochondrial DNA is not completely out of the
modern human range, just on its extreme periphery."

The finding in Portugal last year of a 24,500-year-old early modern
human child with distinctive Neanderthal characteristics, published by
Trinkaus and European colleagues in June 1999, strongly supports the
conclusion that Neanderthals and early modern humans both could and did
share mates when they came into contact.

"Not only do we have the skeleton of a child in Portugal showing
characteristics of common descent, but now we have evidence of the two
groups coinciding in central Europe for several millennia, allowing
plenty of time for the populations to mix," said Trinkaus, a Washington
University professor of anthropology in Arts and Sciences.

The new Croatian findings also raise the question of who created the
ancient tools unearthed at the Vindija cave site, located about 34 miles
north of the Croatian capital of Zagreb. Neanderthals are commonly
associated with relatively crude stone tools, while early modern humans
made more sophisticated stone and bone tools.

The Vindija site produced both kinds of tools, including a beveled bone
probably used as the tip of a spear. "The big question is: 'Why do we
have a combination of tools?'" Smith said.

"It's possible Neanderthals developed all these tools or got the bone
tools through trade with moderns," he added. Both of these
possibilities run counter to the generally accepted idea that
Neanderthals could not produce bone or use more sophisticated stone and
bone tools.

Smith and Trinkaus conceived of the research project, secured
permission for dating of fossils and assembled the research team. Other
team members are Ivor Karavanic at the University of Zagreb and Maja
Paunovic of the Croatian Academy of Sciences.

Copyright 1999, UniSci

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By Trevor Palmer, Nottingham Trent University, UK (10/28/99)

Paper presented at the SIS Silver Jubilee conference at Easthamstead Park, 19 September 1999

CCCMENU CCC for 1999