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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