PLEASE NOTE:


*

CCNet, 50/2000 -  17 April 2000
-------------------------------


     "When William Blake said that one could see the world in a grain
     of sand, he was describing what 'meteoriticists' -- those who
     study meteorites -- do for a living. Often that 'grain of sand',
     even if it is fist-sized, is all they have to go on. Now John
     Bridges and Monica Grady from the Natural History Museum in London
     have used chunks of martian rock that fell to Earth nearly 90
     years ago to reconstruct a history of the Red Planet over 1.3
     billion years ago -- one that includes water-covered flood plains.
     Some of these rocks come from a meteorite that broke up in the
     atmosphere over Nakhla in Egypt in 1911. About forty stones fell
     in the Nakhla shower, one of them reportedly hitting and killing a
     dog. H. G. Wells notwithstanding, this seems to be the only known
     fatality of martian origin -- for the Nakhla meteorite is thought
     to be a lump of martian rock."
          -- Philip Ball, Nature, 14 April 2000


(1) CASSINI MAKES IT THROUGH THE ASTEROID BELT
    Ron Baalke <baalke@jpl.nasa.gov>

(2) TAKE LIFE ON MARS WITH A PINCH OF SALT
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(3) SEARCH FOR LIFE ON MARS WON'T BE CHEAP
    SpaceDaily, 17 April 2000

(4) QUALITY OF THE FOSSIL RECORD THROUGH TIME
    M.J. Benton et al., UNIVERSITY OF BRISTOL

(5) TIMING THE END-TRIASSIC MASS EXTINCTION
    J. Palfy et al., HUNGARIAN NATURAL HISTORY MUSEUM

(6) DELAYED BIOLOGICAL RECOVERY FROM MASS EXTINCTIONS
    J.W. Kirchner & A. Well, UNIVERSITY OF CALIF BERKELEY

(7) SOUTH EAST ASIA IMPACT 800,000 YEARS AGO
    Michael Paine <mpaine@tpgi.com.au>

(8) COW FARTS: AN INTERESTING WAY TO DETECT LIFE
    Larry Klaes <lklaes@bbn.com>

(9) AND FINALLY: ANOTHER ECO SCARE BITES THE DUST -
    EUROPE FACES MASSIVE POPULATION DECLINE
    British Medical Journal 320:891, April 2000


==========
(1) CASSINI MAKES IT THROUGH THE ASTEROID BELT

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

MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov

                Cassini Mission Status
                    April 14, 2000

     NASA's Cassini spacecraft, currently en route to Saturn, has
successfully completed its passage through our solar system's
asteroid belt between Mars and Jupiter.

     This makes Cassini the seventh spacecraft ever to fly
through the asteroid belt.  Before NASA's Pioneer 10 spacecraft
successfully passed through the region in 1972, it was not known
whether a spacecraft could survive the trip.

     The belt contains a significant concentration of asteroids. 
Nonetheless, the area is not considered a hazard to spacecraft. 
Engineers did not make any adjustments to Cassini as it passed
through the region, except the spacecraft's cosmic dust analyzer
was reoriented whenever possible to better study the environment. 
A cover over Cassini's main engines has been in place at all
times since launch except when main engine firings were
performed.  The cover protects the engines from any possible
impacts.

     "I'm glad we've passed through it, but it's pretty routine. 
There's a lot of material in the belt, but there's also an awful
lot of space out there," said Cassini Project Manager Bob
Mitchell at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

     The spacecraft entered the belt in mid-December and while it
was in the area, Cassini's camera imaged the asteroid 2685
Masursky.  Data gathered provided scientists with the first size
estimates on the asteroid and preliminary evidence that it may
have different material properties than previously believed.
    
     Cassini remains in excellent health as it continues its
seven-year-long journey to Saturn. Launched October 15, 1997,
Cassini has already flown by Venus and Earth before heading
toward a flyby of Jupiter on December 30, 2000.  The giant
planet's gravity will bend Cassini's flight path to put it on
course for arrival into orbit around Saturn on July 1, 2004. 

     Cassini's mission is to study Saturn, its moons, its rings,
and its magnetic and radiation environment for four years. 
Cassini will also deliver the European Space Agency's Huygens
probe to parachute to the surface of Saturn's moon Titan on
November 30, 2004.  Titan is of special interest partly because
of its many Earth-like characteristics, including a mostly
nitrogen atmosphere and the presence of organic molecules in the
atmosphere and on its surface.  Lakes or seas of ethane and
methane may exist on its surface.

     The mission is a joint endeavor of NASA, the European Space
Agency and the Italian Space Agency.  The Cassini orbiter, built
by NASA, and the Huygens probe, provided by the European Space
Agency (ESA), were mated together and launched as a single
package from Cape Canaveral, Fla. Cassini's dish-shaped high-gain
antenna was provided for the mission by the Italian Space Agency.

     The mission is managed by JPL, a division of the California
Institute of Technology.  More information about the Cassini
mission is available at http://www.jpl.nasa.gov/cassini .

==============
(2) TAKE LIFE ON MARS WITH A PINCH OF SALT

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

[http://helix.nature.com/nsu/000420/000420-2.html]

From NATURE, 14 April 2000

By PHILIP BALL

When William Blake said that one could see the world in a grain of
sand, he was describing what 'meteoriticists' -- those who study
meteorites -- do for a living. Often that 'grain of sand', even if it
is fist-sized, is all they have to go on.

Now John Bridges and Monica Grady from the Natural History Museum in
London have used chunks of martian rock that fell to Earth nearly 90
years ago to reconstruct a history of the Red Planet over 1.3 billion
years ago -- one that includes water-covered flood plains.

Some of these rocks come from a meteorite that broke up in the
atmosphere over Nakhla in Egypt in 1911. About forty stones fell in
the Nakhla shower, one of them reportedly hitting and killing a dog.
H. G. Wells notwithstanding, this seems to be the only known fatality
of martian origin -- for the Nakhla meteorite is thought to be a lump
of martian rock.

This kind of trans-planetary transfer is believed to result from the
impact of asteroids or comets on a planet, which throws out material
fast enough to escape the planet's gravitational field. Ejected
material can then be captured by the gravitational tug of another
planet.

The dozen or so known meteorites thought to have originated on Mars
are a priceless resource for scientists trying to decode its history.
Two other meteorites -- Governador Valares, found in Brazil in 1958,
and Lafayette, found in the geological collection at Purdue
University in the USA in 1931 -- seem to be very similar to the
Nakhla stones, and they probably all came from the same lump of Mars.

By analysing the chemical and radioisotope composition of this group,
called the nakhlites, researchers have deduced that they are made of
rocks that crystallized from a lava flow on Mars 1.3 billion years
ago, and that they were ejected from the planet 11 million years ago.

So the nakhlites reflect what the martian environment was like over a
billion years ago. Some of the minerals in the nakhlites appear to
have been formed by the action of water. These minerals consist of,
or are derived from, water-soluble salts such as carbonates,
phosphates, sulphates and sodium chloride (halite). On Earth, such
salts can be precipitated when bodies of briny water evaporate and
form deposits called evaporites.

But whether evaporites exist on Mars is unclear [see 'White
Elephant', Nature Science Update 10 April 2000]. If they do, this
would imply that Mars once had lakes, if not entire oceans on its
surface -- wherein primitive life might have arisen. There are
several other reasons to believe that, a billion years ago or more,
Mars might have supported liquid water under a thicker atmosphere that
staved off freezing. The dry surface today is, for example, laced
with channels that look like dried-up river beds.

But no one knows whether Mars knew warm, wet days only very early in
its 4.6-billion-year history, or whether (if they occurred at all)
they persisted until more recently. The longer Mars was wet, the
greater are the chances that life existed on the planet.

Last year Bridges and Grady proposed that the salts in the nakhlites
might be the signature of an interaction between the rock-forming
lava and pre-existing evaporite deposits, implying that there need
not have been any water around on Mars when the rock solidified 1.3
billion years ago.

Now they suggest instead that the nakhlite salts were formed at low
temperatures, by the evaporation of salty water above the cooling
igneous rock. This would require that Mars was still warm and wet 1.3
billion years ago, even if only transiently.

"Primitive life may have existed on evaporite deposits [on Mars] as
they have experienced the past presence of liquid water," Bridges and
Grady say in the journal Earth and Planetary Science Letters[1]. Some
bacteria can survive conditions this salty on Earth. In fact it has
been claimed, controversially, that the Nakhla meteorite also
contains features that look like bacterial remains. Bridges and
Grady's work implies at least that the meteorite may have come from a
location wet enough to make this feasible.

[1] Bridges, J. C. & Grady, M. M. Evaporite mineral assemblages in
the nakhlite (martian) meteorites. Earth Planet. Sci. Lett. 176,
267-279 (2000)

Macmillan Magazines Ltd 2000 - NATURE NEWS SERVICE

============
(3) SEARCH FOR LIFE ON MARS WON'T BE CHEAP

From SpaceDaily, 17 April 2000
http://www.spacedaily.com/news/life-00t1.html

Cameron Park - April 17, 2000 - Mars exploration has turned out to be
much more difficult than NASA had optimistically hoped in the wake of
Pathfinder's stunning success in 1997. With some questioning whether
the search for life has skewed the program towards a sample return
timetable impossible to meet.

FULL STORY at
http://www.spacedaily.com/news/life-00t1.html

=========
TALKING PLANETS: IN THE REALM OF GIANTS

From SpaceDaily, 17 April 2000
http://www.spacedaily.com/news/lunarplanet-2000-00d1.html

Cameron Park - April 17, 2000 - In the inner solar system is
undoubtedly home to life. But whether the outer solar system also
harbors life is firmly in dispute as Galileo offers tantalizing clues
as to what might be out Jupiter way.

FULL STORY at
http://www.spacedaily.com/news/lunarplanet-2000-00d1.html

================
(4) QUALITY OF THE FOSSIL RECORD THROUGH TIME

M.J. Benton*), M.A. Wills, R. Hitchin: Quality of the fossil record
through time. NATURE, 2000, Vol.403, No.6769, pp.534-537

*) UNIVERSITY OF BRISTOL,DEPT EARTH SCI,WILLS MEM BLDG,BRISTOL BS8
   1RJ,AVON,ENGLAND

Does the fossil record present a true picture of the history of life,
or should it be viewed with caution? Raup argued that plots of the
diversification of life were an illustration of bias: the older the
rocks, the less we know. The debate was partially resolved by the
observation that different data sets gave similar patterns of rising
diversity through time. Here we show that new assessment methods, in
which the order of fossils in the rocks (stratigraphy) is compared with
the order inherent in evolutionary trees (phylogeny), provide a more
convincing analytical tool: stratigraphy and phylogeny offer
independent data on history. Assessments of congruence between
stratigraphy and phylogeny for a sample of 1,000 published phylogenies
show no evidence of diminution of quality backwards in time. Ancient
rocks clearly preserve less information, on average, than more recent
rocks. However, if scaled to the stratigraphic level of the stage and
the taxonomic level of the family, the past 540 million years of the
fossil record provide uniformly good documentation of the life of the
past. Copyright 2000, Institute for Scientific Information Inc.

=========
(5) TIMING THE END-TRIASSIC MASS EXTINCTION

J. Palfy*), J.K. Mortensen, E.S. Carter, P.L. Smith, R.M. Friedman,
H.W. Tipper: Timing the end-Triassic mass extinction: First on land,
then in the sea? GEOLOGY, 2000, Vol.28, No.1, pp.39-42

*) HUNGARIAN NATURAL HISTORY MUSEUM,POB 137,H-1431 BUDAPEST,HUNGARY

The end-Triassic marks one of the five biggest mass extinctions, but
current geologic time scales are inadequate for understanding its
dynamics. A tuff layer in marine sedimentary rocks encompassing the
Triassic-Jurassic transition yielded a U-Pb zircon age of 199.6 +/- 0.3
Ma. The dated level is immediately below a prominent change in
radiolarian faunas and the last occurrence of conodonts. Additional
recently obtained U-Pb ages integrated with ammonoid biochronology
confirm that the Triassic Period ended ca. 200 Ma, several million
years later than suggested by previous time scales. Published dating of
continental sections suggests that the extinction peak of terrestrial
plants and vertebrates occurred before 200.6 Ma. The end-Triassic
biotic crisis on land therefore appears to have preceded that in the
sea by at least several hundred thousand years. Copyright 2000,
Institute for Scientific Information Inc.

=========
(6) DELAYED BIOLOGICAL RECOVERY FROM MASS EXTINCTIONS

J.W. Kirchner*) & A. Well: Delayed biological recovery from extinctions
throughout the fossil record. NATURE, 2000, Vol.404, No.6774,
pp.177-180

*) UNIVERSITY OF CALIF BERKELEY,DEPT GEOL & GEOPHYS,BERKELEY,CA,94720

How quickly does biodiversity rebound after extinctions?
Palaeobiologists have examined the temporal, taxonomic and geographic
patterns of recovery following individual mass extinctions in
detail(1-5), but have not analysed recoveries from extinctions
throughout the fossil record as a whole. Here, we measure how fast
biodiversity rebounds after extinctions in general, rather than after
individual mass extinctions, by calculating the cross-correlation
between extinction and origination rates across the entire Phanerozoic
marine fossil record. Our results show that extinction rates are not
significantly correlated with contemporaneous origination rates, but
instead are correlated with origination rates roughly 10 million years
later. This lagged correlation persists when we remove the 'Big Five'
major mass extinctions, indicating that recovery times following mass
extinctions and background extinctions are similar. Our results suggest
that there are intrinsic limits to how quickly global biodiversity
can recover after extinction events, regardless of their magnitude.
They also imply that today's anthropogenic extinctions will diminish
biodiversity for millions of years to come. Copyright 2000, Institute
for Scientific Information Inc.

=============================
* LETTERS TO THE MODERATOR *
=============================

(7) SOUTH EAST ASIA IMPACT 800,000 YEARS AGO

From Michael Paine <mpaine@tpgi.com.au>

Dear Benny,

I am looking for more information about an item posted on CCNet on
6 March 2000 - an major impact in South East Asia 800,000 years ago.
Andrew Glikson has given me some leads. I have also found a 1994
article by Jack Hartung that suggests the Cambodian lake Tonle Sap
could be the impact site. This seems to be dismissed by a NASA
researcher - Charles Schnetzer in a 1999 article.

In any case, according to Hartung, the tektite field (from China to
Australia) suggests a crater at least 40km in diameter. If so, this
would have produced severe regional devastation (as raised by Dr Rick
Potts who argues that the disruption may have fostered innovation in
China, including advanced stone tool making). Global climate
disruption appears likely  since the impactor would have been in the
2km+ range. I would be interested in hearing from any researchers who
have more information about the impact, particularly the
environmental effects. This could have been a very close call for the
human species!

regards
Michael Paine

=============
(8) COW FARTS: AN INTERESTING WAY TO DETECT LIFE

From Larry Klaes <lklaes@bbn.com>

Re: REDUCED FARTING COULD SAVE WORLD, SCOTTISH SCIENTISTS CLAIM
http://dailynews.yahoo.com/h/nm/20000412/sc/science_warming_2.html

This is actually one way that any ETI examining Earth with a
spectroscope could find indications of life on our planet, as methane
is produced by living beings.

So the question is, should we stop cow farts to keep our planet from
overheating, or do we let them continue in the hope that it will
attract the attention of ETI who want to send beacons to make the
initial contact with humanity?

- Larry

==============
(9) AND FINALLY: ANOTHER ECO SCARE BITES THE DUST -
    EUROPE FACES MASSIVE POPULATION DECLINE

From British Medical Journal 320:891, April 2000
http://www.bmj.com/cgi/content/full/320/7239/891

Spain faces massive decline in population

By Xavier Bosch, Barcelona

The Spanish population will decrease by 9.4 million in the next 50
years, according to a report released last month by the United Nations'
population division. This represents a 24% net loss in its current
population.

The reason is the low birth rate of the country, which at 1.2 children
per woman is one of the lowest in the world.

Joseph Chamie, director of the UN population division, said: "In 2050,
Spain will be the country with the highest percentage of old people in
the world." Currently, the over 65 age group makes up 17% of the
Spanish population. If current trends continue, this will rise to 37%
by 2050, which represents a total increase of 117% of this age group by
that year.

Although Spain's situation is the most extreme, it is mirrored by
developments elsewhere in Europe. The number of people aged over 65 is
going to increase, in the same period, by 104% in Switzerland, 92% in
Italy, 73% in Germany, and 56% in the United Kingdom.

To maintain a constant population size, Spain should accept an average
of 170,000 immigrants a year during the next 50 years. However, to
maintain a constant working age population (15-64 years), an average of
260,000 immigrants a year would be needed.

Moreover, to maintain the current potential support ratio (the number
of people of working age per older person), Spain should accept an
annual average of 1.58 million immigrants until 2050. This figure is
totally "unattainable," said Mr Chamie. "Clearly, it is impossible
(sic!) to sort out the problem of the progressive ageing of the Spanish
population by means of immigration. Other European countries such as
Italy and Germany will cope with a similar handicap," he said.

The UN report, Replacement Migration: Is it a Solution to Declining and
Ageing Populations?, examines the situation of low fertility countries
(those with fewer than 2.1 children per woman) and tries to find out
whether replacement migration (international migration needed by a
country to prevent population decline and ageing resulting from low
fertility and mortality rates) may be a solution.

According to the report, the populations of most developed countries
are projected to become smaller and older as a result of low fertility 
and increased longevity. Italy is projected to register one of the
largest population declines in relative terms, losing 28% of its
population between 1995 and 2005. By 2050, 35% of Italians will be aged
over 65, compared with 18% today.

Thus, by that date, Spain and Italy will be the countries with the
highest proportions of elderly people in the world (37% and 35%
respectively). To maintain the size of its working age population,
Italy would require 6500 immigrants per million inhabitants annually;
Germany would need 6000 per million inhabitants.

The report indicates that population decline is inevitable in Europe in
the absence of replacement migration. Although fertility may increase
again in the coming decades, "few believe that it will recover
sufficiently in most countries to reach replacement level in the
foreseeable future."

The report says, however, that maintaining potential support ratios at
current levels through replacement migration alone seems out of reach
"because of the extraordinarily large numbers of immigrants that would
be required."

Hence, said Mr Chamie, "if we rule out massive immigration, the only
solution to maintain the potential support ratios at current levels in
most European countries would be to increase the upper limit of the
working age population to roughly 75 years of age."

Replacement Migration: Is it a Solution to Declining and Ageing
Populationsis available at www.un.org/esa/population/migration.htm.


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