CCNet DIGEST, 1 June 1998

    Tony Beresford <starman@CAMTECH.NET.AU>

    Duncan Steel <>

    From New Scientist, 30 May 1998

    The Sunday Times, 31 May 1998

    SCIENCE, 22 May 1998

    Andrei Razvan <>

    Andrew Yee <>

    Andrew Yee <>

From Tony Beresford <starman@CAMTECH.NET.AU>
The West Australian Geological survey has renamed the Teague ring, as
the Shoemaker impact structure, in honour of the astro-geologist Gene
Shoemaker. This crater is some 30Km across about 100km North East of
the small town of Wiluna, West Australia. Gene & Carolyn did field work
on the structure in 1985 and 1995. They had planned to visit it again
on there 1997 visit to Australia, but these plans were of course
cancelled by the road accident in which Gene died.
Tony Beresford


From Duncan Steel <>

Dear Benny,

With respect to the Press Agency News story you circulated...

>"The last big asteroid impact was in 1908 in Siberia. It had the
>impact of 2,000 Hiroshima bombs. Two hours later and it would have 
>wiped out St Petersburg, killing 200,000 people," he [Peiser] says.

This is an oft-stated 'fact' which is incorrect. If the Tunguska
object had in fact been two hours 'later' (by which one understands
two hours' motion back along its orbit, or the time of perihelion
passage for the orbit being two hours greater) then it would have
missed the Earth by a long way. As it passed by the point in space
that the Earth had occupied two hours earlier, the Earth would have
been about 211,000 km (or over 16 Earth diameters) away.

The source of the above misunderstanding appears to be that people
equate (incorrectly) the time required to have produced an entry over
St Petersburg with the difference in longitude (or some variant on
that: Tunguska & St Petersburg are actually about 60 degrees apart in
longitude), whereas actually the Earth's orbital motion rather than
spin is the dominant factor. At the time of the arrival of the object
St Petersburg was still on the nightside of the Earth and so could
not have been struck by an object with a radiant in the proximity of
the solar direction. A better concept would be to consider the object
having been retarded by only a few minutes, in which case Tokyo or
Los Angeles could have been in the firing line (e.g., a three minute
delay would have put ground zero about 5,000 km east of Tunguska,
although this all depends upon the assumed orbit/entry angle for the

The energy of the Tunguska event, according to best estimates, was
about ONE thousand times the Hiroshima bomb (12.5 Mt against 13 kT),
although one could choose published values to derive higher or lower
ratios. But there's no need to exaggerate! One thousand is impressive

>but because we don't know when the last large impact was, it is
>impossible to calculate exactly when the next one is due.

This, of course, is garbage, for which the journalist bears
responsibility I am sure. It is wrong on several counts.

Duncan Steel


From From New Scientist, 30 May 1998


Will Bruce save us? If we don't know where they are, we stand no
chance against asteroid impacts

At the climax of Spielberg's latest production Deep Impact, a
2-kilometre wide fragment of a comet plunges into the Atlantic,
creating a 300-metre high tidal wave which tears into New York.
Spectacular mayhem follows as the Statue of Liberty loses her head
and skyscrapers tumble. Most of the population of the East Coast of
the US is swept away as it vainly tries to flee.

The prospects don't look good for survivors on high ground either. A
far larger fragment of the same comet is about to hit Canada. The
blast will fill the atmosphere with dust and blot out the Sun for two
years. The ensuing dark and freezing cold, the US President explains
in a live television address, will kill off all plants and animals.
The public (except for a chosen few, a couple of elephants and
various wildlife destined for an underground Ark) must now fend for

Is this just another overblown Hollywood disaster movie carried away
by its own special effects? Not this time. The film is based on the
novel Hammer of God by Arthur C. Clarke and its makers took advice
from some of the world's greatest experts on cometary impacts,
including Carolyn Shoemaker and the late Gene Shoemaker. The comet is
the sort of size that will hit the Earth every 100 000 years or so.
The tidal wave is what you would expect to result when a comet hits
the ocean. And the effect of the impact of the larger fragment
squares with the mass extinctions recorded in the fossil record.

That leaves one puzzle. If Hollywood can take the science of cometary
impact so seriously, why can't scientific funding bodies?

At the moment, we are relying on a handful of underfunded enthusiasts
to monitor the threat from approaching asteroids and comets. In
Australia, the only group scouring the southern skies has run out of
cash altogether. And in the US, less than $1 million a year is being
spent on two programmes. Spacewatch at the University of Arizona uses
a telescope built in 1921, while the Jet Propulsion Laboratory's NEAT
project borrows a few nights a month observing time on air force
telescopes designed to spot Soviet satellites. Europe has only ODAS,
a tiny Franco-German effort using a telescope in the south of France.

Even stranger, it would take only a modest global spend--perhaps $50
million spread over ten years--to boost these projects so we could
find out whether the Earth does indeed face any serious risks within
the foreseeable future. A truly global disaster--an "extinction-level
event" to borrow the jargon of Deep Impact--would result if the Earth
were hit by anything larger than half a kilometre across.

There are some 2000 asteroids of this size currently passing close to
the Earth. We need to know where they are and how their orbits are
shifting to find out if they will hit the Earth at some time in the
next century or so. And if any turn out to be on a collision course,
we should still have at least a few decades to find a way to divert

But even this won't make the Earth a totally safe place. There are
tens of thousands of much smaller asteroids passing close by that
could cause trouble. Earlier this century, a 100-metre diameter
asteroid exploded at Tunguska in Siberia and flattened about 1800
square kilometres of forest. And we know that many smaller asteroids
hit the Earth. Each year, military satellites see dozens of asteroids
explode in the upper atmosphere, each with a force greater than the
bomb dropped at Hiroshima.

Tracking the smaller asteroids is feasible but it is a much bigger
task. So why not at least start by tracking the really large
asteroids? Their orbits change slowly so once the job is done, it
need not be repeated for a century. The only major worry left would
be a long-period comet that appeared from nowhere. But they are very

Thanks to the recent alarm over asteroid XF11, public interest is
already high. And in July, another film, Armageddon, will be upon us.
This time the Earth is threatened by an asteroid "the size of Texas"
with only Bruce Willis to keep us from disaster. But not to worry: as
the real asteroids line up to decimate our planet, we can take
comfort in the knowledge that the movie's budget was far larger than
the money needed for the asteroid-tracking programme.

(C) 1998 New Scientist


From The Sunday Times, 31 May 1998

Nasa is increasing its efforts to spot any comets or asteroids that
could wipe out human life in a collision with Earth. Mark Prigg reports

THE American space agency Nasa is redoubling its efforts to find
asteroids and comets that may be on a collision course with Earth.

Its Near-Earth Asteroid Tracking (Neat) project uses an automated
camera and telescope on Mount Haleakala in Maui to try to locate these
hazards, but it operates for just six nights a month.

However, Nasa has decided that in the light of public interest in the
possibility of a stray asteroid hitting the Earth, it needs to improve
its efforts.

It is now widely accepted that large asteroids, several kilometres in
diameter, have struck the Earth and caused mass extinctions. One such
rock, 5km to 10km wide, is believed to have created the catastrophe
that wiped out the dinosaurs 65m years ago.

Scientists believe that if they are early in spotting an asteroid bound
for Earth they could throw it off course with nuclear explosions.

According to Steven Pravdo, the Neat project manager at Nasa's Jet
Propulsion Laboratory (JPL) in Pasadena, California, a new computer
system combined with plans to operate the telescope for 18 nights a
month mean that 90% of potentially hazardous asteroids should be

"With the new computer system we can double the amount of sky we look
at each night, which currently amounts to 40 gigabytes of data, enough
to fill 70 CD-Roms," says Pravdo.

Nasa will try to spot asteroids with a diameter of more than 1km
approaching the Earth. At this size, a rock striking the Earth would
wreak massive destruction. Even if it missed an urban area, the dust
cloud or tidal wave caused by the impact could kill hundreds of
thousands of people.

The telescope spots moving bodies by observing the same part of the sky
three times over an hour. The three images are then compared to find
out which objects are moving across the sky.

So far, the system has spotted more than 25,000 objects near the Earth,
including two comets and 30 asteroids.

According to Pravdo, the team was also responsible for last year's
discovery of a new aten, a type of asteroid with an orbit around the
sun far smaller than the Earth's, making it very hazardous.

"The aten we discovered this year passed within 5m kilometres of Earth
in May. While this is in no way hazardous to us it is still fairly
close, and because of the small orbit of atens they always stay close
to Earth, so we need to keep an eye on them."

Pravdo also hopes to be able to use the new system to track comets
coming from the Oort cloud, a region of space beyond Pluto thought to
hold trillions of comets. They travel in very long paths and often
appear very quickly near Earth.

"We don't usually get any warning from these comets, but the Neat
upgrade should definitely help us track them a little more
successfully," he says.

The new computer system uses four 300Mhz processors to analyse data
from the telescope in real time.

The telescope used by Neat is a device with a one-metre diameter and is
operated by the US Air Force. It is located two miles above the Pacific

Nasa conducts a monthly scan of space to look for potentially dangerous
asteroids, as well as any comets.

The American National Research Council has condemned stories that
appeared in the media recently about a possible collision with an
asteroid in 2028. It is calling on scientists and reporters to be more
responsible and cut down on wild speculation.

The council believes that Nasa's Neat programme and several new
telescopes will lead to the discovery of hundreds of new asteroids in
the coming years.

The report calls for scientists to work closely together to evaluate
risks before letting the public know.

The council also called for Nasa to spend more money on researching
asteroids, including missions to fetch samples and even the possiblity
of sending astronauts to nearby asteroids.

(C) 1998 Times Newspaper Ltd


From SCIENCE, 22 May 1998

Richard A. Kerr

Earthquakes were once thought to keep to themselves, striking on a
schedule determined only by the history of each particular fault. Then
seismologists began to realize that every rupturing fault communicates
with neighboring faults, instantly reaching out tens or hundreds of
kilometers to hasten or delay distant earthquakes (Science, 16 February
1996, p. 910). Now a group of geophysicists suggests that these lines
of communication extend even farther--and carry much, much slower

Big quakes can trigger other quakes thousands of kilometers away and
decades later, according to calculations presented on page 1245 of this
issue of Science. Geophysicists Fred F. Pollitz and Roland Bürgmann of
the University of California, Davis, and seismologist Barbara
Romanowicz of UC Berkeley simulated how stress travels through deep,
viscous rock. They found that the great earthquakes that struck the far
North Pacific in the 1950s and '60s could have set off wave that
triggered a pulse of seismic activity in California in the 1980s.

"It's an exciting possibility," says seismologist Thomas Hanks of the
U.S. Geological Survey (USGS) in Menlo Park, California. If the reach
of big quakes extends that far, seismologists may be able to make more
sense of the comings and goings of earthquakes worldwide, he adds.
Researchers are intrigued, though not yet completely convinced. "It
could be right," says tectonophysicist Wayne Thatcher of the USGS, "but
I think it has a ways to go before being a persuasive argument."

Researchers have long recognized a potential transmission route for
long-distance messages among faults: the thin layer of soft rock at
depths of 80 kilometers or more called the asthenosphere. There,
temperature and pressure combine to soften rock so that, although still
solid, it slowly flows over decades. The more rigid tectonic plates
that make up Earth's surface, such as the great Pacific Plate,
glide along on this softer layer.

But plates don't slide smoothly at their edges. They stick to each
other, build up stress, and then jerk forward in earthquakes. The quake
redistributes stress nearby, adding stress in some places and relieving
it in others. For example, between 1952 and 1965, four great quakes
struck along the Aleutians and the Kamchatka Peninsula, where the
Pacific Plate is diving beneath the North American Plate. After each
quake, the Pacific Plate adjusted to the new plate positions
immediately, stretching like a sheet of rubber and triggering flow in
the asthenosphere below. Spreading outward through the asthenosphere
like the ripple of a pebble dropped in a pond, the wave created by this
flow could transmit the stress induced by the quakes.

"That [stress] wave has to exist," says Bürgmann. "The only question is
how strong is it?" To find out, the group created a computer simulation
of elastic plates, ductile asthenosphere, and large earthquakes in the
northern North Pacific. In the model, the stress wave generated by the
quakes moved southward across the Pacific and northward under the
Arctic Ocean at a rate that depended on the viscosity of the
asthenosphere. When researchers plugged in a viscosity that Romanowicz
calls "reasonable but a bit on the low side" of current estimates, the
crest of the stress wave entered the eastern Arctic Ocean in the 1970s;
it passed off British Columbia around 1975, and California around 1985.
Wherever the wave passed, it briefly accelerated plate motions, which
could have spurred earthquake activity.

The timing is a good fit to surges of seismic activity, say Pollitz and
his colleagues. According to the model, the wave may have triggered the
surge of magnitude 5 and greater quakes observed in the eastern Arctic
Basin in the 1980s. To the south, the wave's progress--marked by
accelerations of only a couple of millimeters per year--could be seen
in pulses of increased seismicity in Northern California in the 1970s
and Southern California in the 1980s.

Even the types of earthquakes seemed to fit stress-wave triggering,
says the group. The Southern California seismicity mostly took the form
of quakes on faults other than the San Andreas. The sides of these
faults move chiefly up and down rather than sideways, as the San
Andreas does. That feature of the seismicity was noted in 1995 by
seismologists Frank Press of the Washington Advisory Group in
Washington, D.C., and Clarence Allen of the California Institute of
Technology in Pasadena, who speculated that a stress wave oriented to
favor vertical fault motions might be responsible. The wave set off by
the great Alaskan quakes fits the bill, Pollitz's team says. "The
whole thing seems to hang together," says Press.

But others point out that the correlation of the passing wave with a
flurry of seismicity could be chance. "There have been many interesting
patterns in seismology that have turned out to be wonderful
coincidences," says seismologist Lucile Jones of the USGS in Pasadena.
And the stress wave, dampened by distance, seems too weak to trigger
quakes, other researchers say. The extra strain added by the wave would
be "really small," says Thatcher, perhaps a factor of 10 smaller than
what's assumed to trigger quakes at short range.

"Yes, the strain changes are small," concedes Romanowicz, "but I don't
think anyone has a definite idea of how much strain you need to trigger
an earthquake." Bürgmann adds that a coincidence is unlikely, because
seismicity along the entire west coast fits the stress-wave theory.

Further tests of this bold idea are in the works. Although existing
geodetic networks weren't sensitive enough to catch the subtle stress
changes signaling the arrival of the wave, says Bürgmann, current
systems should record its departure in the coming decade. Then it
should become clear whether distant earthquakes are the interfering
busybodies he and his colleagues suspect they are.

Volume 280, Number 5367 Issue of 22 May 1998, pp. 1194 - 1195
©1998 by The American Association for the Advancement of Science.


From Andrei Razvan <>
Here are some news about a new finding in Romania. Since 1989 some
archaeologists are working in the Cluj County, Mocs-Palatca region in a
archaeological area named "Togul lui Mândrusca" dated from the bronze
ages. Mainly they discovered surface houses and stone and bronze tools.
The most important discovery was a little place where ancient people
made bronze tools. These days the team have found there a stony
meteorite weighting 0.5 Kg and composed mainly from olivine, feldspat
and magnetite. They are searching if this meteorite has any connection
with the Mocs meteorite rain (1882) but the evidence shows the stone
was in the little factory.
Best Regards,    Andrei


From Andrew Yee <>

University of Delaware
Newark, Delaware

Contact: Ginger Pinholster, (302) 831-6408,

FOR VIDEOTAPE, CALL (302) 831-6408

Cosmic cloud could burst Earth's 'breathing bubble,' new Bartol computer
simulation shows

BOSTON, MASS. -- A colorful new computer animation -- created by Gary
P. Zank of the Bartol Research Institute at the University of Delaware
-- shows how even a small cosmic cloud could suddenly burst the
"breathing bubble" that protects life on our planet.

The simulation, presented today during the American Geophysical Union's
Spring meeting, also should help guide the spacecraft, Voyager 1 and
Voyager 2, through a series of shock waves and a massive "wall" in
space nearly two decades from now, says Zank, an associate professor at
Bartol and a leading theoretical astrophysicist.

Ongoing studies of Earth's "cocoon" might someday reveal whether close
encounters with cosmic clouds cause periodic extinctions, according to
Zank, who earned a National Science Foundation Presidential Young
Investigator Award in 1993 and a Zeldovich Medal in 1996.

"We're surrounded by hot gas," Zank notes. "As our sun moves through
extremely 'empty' or low-density interstellar space, the solar wind
produces a protective bubble -- the heliosphere around our solar
system, which allows life to flourish on Earth. Unfortunately, we could
bump into a small cloud at any time, and we probably won't see it
coming. Without the heliosphere, neutral hydrogen would interact with
our atmosphere, possibly producing catastrophic climate changes, while
our exposure to deadly cosmic radiation in the form of very high-energy
cosmic rays would increase."

Zank's startling computer simulations were initially developed to
support the Voyager spacecraft, deployed as part of the Voyager
Interstellar Mission. Even as the sun rolls freely through wide-open
space, he explains, the Earth's ever-changing bubble generates shock
waves and an enormous wall of hydrogen gas. The wall, he says, will
sweep past Voyager 1 around 2015 -- several years later than previously

Rather like a lung, the heliospheric bubble breathes, but in a highly
arythmic fashion, because of an 11-year periodic cycle of solar wind
properties. By simulating this breathing bubble, Zank says, he can
predict the location of the boundary between the solar wind and the
vast interstellar medium of space, which should help the National
Aeronautics and Space Administration (NASA) prepare Voyager 1. The
battery-operated vehicle is running out of power, Zank notes. To make
the most of its instruments, NASA researchers must conserve energy, by
switching systems on and off.

Rowdy Space Clouds

Every 66 million years or so, the solar system traces a regular path
through the galaxy, oscillating up and down as it sails through "all
sorts of environments," Zank reports. Over the past 5 million years, he
says, "We've had incredibly smooth sailing" because the sun was lolling
through an interstellar medium containing less than one atom per cubic
inch of space. That's empty space, indeed: Even wispy clouds are 100
times more dense. Currently, Zank says, the solar system is in a region
of space containing between 3 and 4 particles per cubic inch.

"Space," Zank notes, "is full of clouds." One particularly troublesome
cloud region, located in a star-forming region towards the Aquila Rift,
clearly is headed our way, according to Zank. Pushed by galactic wind,
the cloud may collide with Earth's protective bubble within the next
50,000 years, he says, and some researchers think we could encounter
fluffier knots of gas -- containing 10 to 100 particles per cubic inch
of space -- far sooner. Our immediate or local interstellar environment
is chock-full of gas clusters known as the Local Fluff, Zank points
out, and existing instruments aren't sensitive enough to detect
extremely small clouds. Consequently, Zank says, "We won't know that
our heliosphere is collapsing until we see highly elevated levels of
neutral hydrogen and cosmic rays, and a hydrogen wall in the vicinity
of the outer planets."

Did a rogue cloud wipe out the dinosaurs? In 1939, British cosmologist
Sir Fred Hoyle suggested that cosmic collisions with clouds may
obliterate the heliosphere every now and then. Zank agrees. "The
protective solar wind would be extinguished, and cosmic radiation might
lead to gene mutations," he says. "Hydrogen would bombard Earth,
producing increased cloud cover, leading perhaps to global warming, or
extreme amounts of precipitation and ice ages. We can't predict every
scenario at this point."

A Bon Voyage for Voyagers 1 and 2?

Using powerful new number-crunching computers at Bartol, as well as
systems at national supercomputing centers, Zank created two animations
to show the heliosphere in empty space some 5 million years ago, and in
a dense cloud containing 10 particles per cubic inch. In clear space,
the sun blows solar wind at supersonic speeds, thereby creating the
heliosphere, which Zank describes as "a funny, bullet-shaped bubble."
When the interstellar medium crashes into this bubble, he explains, "it
suddenly veers upward and around, like water flowing around a rock in
the river." The result, he says, is a system of massive shock waves and
a hydrogen wall, which could be 50 times thicker than the distance
between the Earth and the sun.

Undisturbed by clouds, the heliosphere appears to take a breath every
11 years, as fluctuations in solar-wind speeds produce a gentle,
arhythmic motion, Zank says. Flowing outward, shock waves push the wall
and interstellar boundaries farther into space until at last they break
and wane, allowing the boundary to contract. This shifting region
between the heliosphere and its boundary may filter hydrogen through a
process known as "charge exchange," in which neutral hydrogen and
charged particles swap an electron, and so, change identities.

Earth's protective bubble seems to gasp spasmodically in a dense cloud,
so that it collapses and reforms every 331 days, Zank says. The weight
of neutral hydrogen, pressing down on the lighter solar wind, "would
drive great rollups of instability," he says. "This well-defined
heliosphere structure would disappear and reappear, at times
obliterating the hydrogen-filtering region."

Understanding Cosmic Evolution

Zank's colorful images aren't likely to help us avoid a cloud
collision, but they may spark a new appreciation for life. On Earth, he
says, "These days, and the last 5 to 10 millioin years, have been
extremely benign, in an astrophysical sense, and we need to make the
most of them, by learning all we can about this cocoon in which we
live." Moreover, Zank says, "We can't predict our future until we
understand our cosmic evolutionary history."

The new Bartol simulations were obtained by solving an extremely
complicated, highly nonlinear system of coupled equations. First, Zank
assembled key information about conditions in interstellar space, such
as the speed, density and temperature, measured by instruments on the
spacecraft, Ulysses, and extrapolated from telescope data. Then, he
used that information in his equations, which were fed into computers,
along with a second data set describing conditions closer to Earth.
Zank's research was supported by the National Science Foundation and


From Andrew Yee <>

Applied Physics Laboratory
Johns Hopkins University
Laurel, Maryland

Helen Worth
JHU/APL Office of Public Affairs
Phone: 240-228-5113
Fax: 240-228-6123.

Donald Savaage
NASA Headquarters, Washington, DC
Phone: 202-358-1547


As the Near Earth Asteroid Rendezvous (NEAR) spacecraft silently races
toward asteroid 433 Eros, it is making interplanetary history. An April
1 sighting from an Earth-based telescope made NEAR the most distant
man-made object ever detected by optical means.

The spacecraft was seen by Gordon Garradd of Loomberah, New South
Wales, Australia, at 20,909,000 miles (33,650,000 kilometers) from
Earth. Garradd was aided by NEAR's 100 square feet of solar panels that
fortuitously reflected sunlight directly at Earth for a few minutes
following the spacecraft's successful 12th trajectory correction
maneuver. (For images of the Milky Way star field with NEAR's position,
see Web site:

The previous record for sighting of a man-made object was the detection
of the Galileo spacecraft several days before its second Earth swingby
on Dec. 8, 1992. Galileo was imaged at a distance of 8.06 million
kilometers with the University of Arizona's 70-inch Spacewatch

NEAR, now traveling at approximately 30 thousand mph (relative to
Earth), has completed more than 1 billion miles of its journey since
its launch on Feb. 17, 1996, and is more than halfway to a Jan. 10,
1999, rendezvous with asteroid 433 Eros. NEAR will be the first
spacecraft to orbit an asteroid and to study its composition and
characteristics at close range (as close as 9 miles from the surface).

David Dunham of the APL Mission Design Team says, "Excitement is
building among the NEAR operations and science teams now that NEAR has
literally turned the corner with last January's Earth swingby and is
now closing in on Eros." Rendezvous activities are well under way, he
says. "It's the last leg of NEAR's interplanetary journey, and work is
nearly complete on the complex plans for the Eros rendezvous and early
orbital phase operations."

NEAR, the first spacecraft powered by solar cells to operate beyond the
orbit of Mars, has already experienced a cosmic encounter. On June 27,
1997, NEAR flew by asteroid 253 Mathilde coming to within approximately
750 miles (1200 kilometers), the closest ever to an asteroid. A
deep-space maneuver on July 3, 1997, took NEAR back toward Earth for a
slinghot gravity assist that put the spacecraft on target for Eros.

The next significant event of the NEAR mission is the detection of Eros
by the spacecraft, which is expected to take place on Aug. 13 of this
year, the 100th anniversary of the asteroid's discovery.

NEAR was the first launch in NASA's Discovery Program of low-cost,
small-scale planetary missions. The spacecraft was built by The Johns
Hopkins University Applied Physics Laboratory, Laurel, Md., which is
also managing the mission.

Visit the NEAR Web site at:

The CCNet is a scholarly electronic network. To subscribe, please
contact the moderator Benny J Peiser at
Information circulated on this network is for scholarly and educational
use only. The attached information may not be copied or reproduced for
any other purposes without prior permission of the copyright holders.
The electronic archive of the CCNet can be found at

CCCMENU CCC for 1998