PLEASE NOTE:
*
CCNet DIGEST, 25 August 1998
----------------------------
(1) DRAFT AO FOR NEAR EARTH ASTEROID RENDEZVOUS
Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
(2) ASTEROID NAMED FOR CAROLYN PORCO
Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
(3) GRADUALISTS STILL UNCONVINCED: 'COSMIC CATASTROPHES INCAPABLE
OF
PRODUCING GLOBAL MASS EXTINCTION'
W.J. Zinsmeister, PURDUE UNIVERSITY
(4) "END-PERMIAN MASS EXTINCTION LASTED LESS THAN 1 MILLION
YEARS"
S.A. Bowring et al., MIT
(5) "END-PERMIAN MASS EXTINCTION LASTED LESS THAN 30,000
YEARS"
M.R. Rampino & A.C. Adler, NASA, GODDARD
INSTITUTE
(6) IMPACT CATASTROPHE AT THE T/J BOUNDARY CANNOT BE RULED OUT
D.J. Mossman et al., MT ALLISON UNIVERSITY
(7) TO BE OR NOT TO BE: THE PHILOSOPHY OF EXTINCTION
G.M. Aitken, UNIVERSITY OF LANCASTER
=================
(1) DRAFT AO FOR NEAR EARTH ASTEROID RENDEZVOUS
From Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
Near Earth Asteroid Rendezvous (NEAR) - DRAFT AO
AO 98-OSS-XX
Release Date: August 20, 1998
Comment Due Date: September 4, 1998
The National Aeronautics and Space Administration (NASA), Office
of
Space Science is releasing a DRAFT Announcement of Opportunity
(AO
98-OSS-XX) for community comment (final release is anticipated in
October 1998) entitled Near Earth Asteroid Rendezvous
(NEAR). This
AO solicits proposals for Participating Scientists on the NEAR
mission whose expertise is sought for reducing and validating
scientific data from the mission; preparing raw and reduced data
for
archiving in NASA=92s Planetary Data System; and analyzing,
interpreting, and publishing scientific results. Participation is
open to all categories of organizations, foreign and domestic,
including educational institutions, profit and nonprofit
organizations, NASA Centers, and other Government agencies. NASA
welcomes comments on the DRAFT AO, which will be available from
August 20, 1998, through September 4, 1998, via the World Wide
Web
site:
http://www.hq.nasa.gov/office/oss/research/open.htm.
For those not having access to the Internet, a printed copy may
be
requested from the program scientist, Thomas H. Morgan, Research
Program Management Division, Code SR, Office of Space Science,
NASA
Headquarters, Washington, DC 20546-0001;
TEL: (202) 358-0828; E-mail: tmorgan@hq.nasa.gov.
Comments may be sent by either postal mail or E-mail to the
program
scientist as listed above; the deadline for receiving comments is
COB
September 4, 1998.
===================
(2) ASTEROID NAMED FOR CAROLYN PORCO
From Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>
University of Arizona
21-Aug-98
ASTEROID NAMED FOR UA SCIENTIST
A Lowell Observatory astronomer has named an asteroid for
planetary
scientist Carolyn C. Porco of The University of Arizona in
Tucson.
Porco designed and produced the Eugene M. Shoemaker Tribute that
flew
on the Lunar Prospector mission to the moon in January.
Ted Bowell of the Lowell Observatory in Flagstaff discovered the
15-mile diameter asteroid in October 1985. Discoverers of
asteroids
get the privilege of naming them, with approval of the Small
Bodies
Names Committee, which is under the authority of the
International
Astronomical Union.
The description for Asteroid 7231 Porco reads:
"Named in honor of Carolyn C. Porco (b. 1953), planetary
scientist at
The University of Arizona. A pioneer in the study of planetary
ring
systems, Porco has made important contributions to our knowledge
of
spokes in Saturn's rings, eccentric ring features in the systems
of
Saturn and Uranus and the azimuthal structure in the rings of
Neptune. Through her contributions to the Voyager project and as
the
team leader for the Cassini imaging system, Porco has been a
leader
in spacecraft exploration of the outer solar system. In 1997, she
originated the idea of sending a capsule containing ashes of E.M.
Shoemaker to the moon aboard the Lunar Prospector spacecraft.
Name
endorsed by the Shoemaker family."
Shoemaker, long a distinguished scientist with the U.S.
Geological
Survey at Flagstaff, was best known for his work on
extraterrestrial
impacts and for his later collaboration with his wife, Carolyn,
in
the study and discovery of comets. He was killed July 18, 1997,
in a
car accident in Alice Springs, Australia, during field research
on
impact crater geology. Carolyn Shoemaker, injured in the
accident,
endorsed the asteroid name.
Porco, quick to note that many planetary scientists have had
asteroids named in their honor, said, "Needless to say, I am
'over
the moon' about this."
======================
(3) GRADUALISTS STILL UNCONVINCED: 'COSMIC CATASTROPHES INCAPABLE
OF
PRODUCING GLOBAL MASS EXTINCTION'
W.J. Zinsmeister: Discovery of fish mortality horizon at the K-T
boundary on Seymour Island: Re-evaluation of events at the end of
the
Cretaceous. JOURNAL OF PALEONTOLOGY, 1998, Vol.72, No.3,
pp.556-571
PURDUE UNIVERSITY, DEPT EARTH & ATMOSPHER SCI, W LAFAYETTE,
IN, 47907
The discovery of a fish bone layer immediately overlying the K-T
iridium anomaly on Seymour Island, Antarctic Peninsula, which may
represent the first documented mass kill associated with the
impact
event, together with new faunal data across the boundary has
provided
new insight into events at the end of the Cretaceous. The
utilization
of a geographical approach and a new graphical representation of
range data has revealed that events at the end of the Cretaceous
were
not instantaneous, but occurred over a finite period of time.
Although the fish bone layer may contain victims of the impact
event,
the absence of ammonites in either the iridium-bearing layer or
the
overlying fish layer suggests that the extinction event at the
end of
the Cretaceous was the culmination of several processes beginning
in
the late Campanian. The impact was the proverbial 'straw that
broke
the camel's back,' leading to the extinction of many others forms
of
life that might have survived the period of global biotic stress
during the waning stages of the Mesozoic if there had not been an
impact. The absence of mass extinction following catastrophic
geologic events in a biotic robust world, such as the Middle
Ordovician Millbrig-Big Bentonite volcanic event suggests that
the
biosphere is remarkably resilient to major geologic catastrophes
with
mass extinction events occurring only when there is a conjunction
of
geologic events none of which might be capable of producing a
global
mass extinction by itself. Copyright 1998, Institute for
Scientific
Information Inc.
=================
(4) "END-PERMIAN MASS EXTINCTION LASTED LESS THAN 1 MILLION
YEARS"
S.A. Bowring*), D.H. Erwin, Y.G. Jin, M.W. Martin, K. Davidek, W.
Wang: U/Pb zircon geochronology and tempo of the end-Permian mass
extinction. SCIENCE, 1998, Vol.280, No.5366, pp.1039-1045
*) MIT, DEPT EARTH ATMOSPHER & PLANETARY SCI, CAMBRIDGE, MA,
02319
The mass extinction at the end of the Permian was the most
profound
in the history of life. Fundamental to understanding its cause is
determining the tempo and duration of the extinction.
Uranium/lead
zircon data from Late Permian and Early Triassic rocks from south
China place the Permian-Triassic boundary at 251.4 +/- 0.3
million
years ago. Biostratigraphic controls from strata intercalated
with
ash beds below the boundary indicate that the Changhsingian pulse
of
the end-Permian extinction, corresponding to the disappearance of
about 85 percent of marine species, lasted less than 1 million
years.
At Meishan, a negative excursion in delta(13)C at the boundary
had a
duration of 165,000 years or less, suggesting a catastrophic
addition
of light carbon. Copyright 1998, Institute for Scientific
Information
Inc.
=====================
(5) "END-PERMIAN MASS EXTINCTION LASTED LESS THAN 30,000
YEARS"
M.R. Rampino*) & A.C. Adler: Evidence for abrupt latest
Permian mass
extinction of foraminifera: Results of tests for the Signor-Lipps
effect. GEOLOGY, 1998, Vol.26, No.5, pp.415-418
*) NASA, GODDARD INST SPACE STUDIES, NEW YORK, NY, 10025
We used published biostratigraphic data on ranges of fusulinids
and
other foraminifera from Permian-Triassic boundary sections in the
southern Alps, Italy, to test the effects of sampling and species
abundance on the record of the timing of the latest Permian
extinction. The number of last occurrences of taxa reaches a
maximum
close to the local base of the Tesero horizon of the Werfen
Formation. Taxa that have less than or equal to 15 %
stratigraphic
abundance (percent of sample intervals in which a taxon occurs)
show
last occurrences well before that level, whereas taxa with more
complete records tend to disappear at or close to that level.
These
results are in agreement with simulations for abrupt extinctions,
as
opposed to gradual or steplike extinction scenarios, and support
predictions of the Signor-Lipps effect, that errors in the end
points
of biostratigraphic ranges can produce range truncations and
apparent
gradual decline preceding a sudden extinction boundary. On the
basis
of estimated sedimentation rates for the Italian sections, the
end-Permian extinctions could have been very sudden (less than or
equal to 30 k.y.), and the disappearance of most latest Permian
foraminifers was most likely coincident with a world wide
ecological
stress event, identified by a global negative delta(13)C anomaly
that
occurs in Italy near the base or within the time-transgressive
Tesero
horizon. Copyright 1998, Institute for Scientific Information
Inc.
==============
(6) IMPACT CATASTROPHE AT THE T/J BOUNDARY CANNOT BE RULED OUT
D.J. Mossman*), R.G. Grantham, F. Langenhorst: A search for
shocked
quarts at the Triassic-Jurassic boundary in the Fundy and Newark
basins of the Newark supergroup. CANADIAN JOURNAL OF EARTH
SCIENCES,
1998, Vol.35, No.2, pp.101-109
*) MT ALLISON UNIVERSITY, DEPT PHYS ENGN & GEOSCI, 67 YORK
ST,
SACKVILLE, NB E4L 1E6, CANADA
Triassic-Jurassic rift basins associated with the breakup of
Pangea
preserve key geological elements of a defining interval in Earth
history. In eastern North America, the Fundy basin is the largest
and
deepest of nine major early Mesozoic basins of the Newark
Supergroup.
Overall, the stratigraphic succession is that of continental
sediments, primarily fluvial, eolian, and playa lacustrine
facies. In
the Fundy basin, the Triassic-Jurassic boundary, as
palynologically
defined, is located within a few metres of the base of the North
Mountain Basalt. In the Jacksonwald Syncline of the Newark basin,
the
boundary is precisely correlated to a ''fern spike'' coincident
with
geologically rapid Late Triassic extinctions. If meteorite impact
is
held to account for extinctions at the Triassic-Jurassic
boundary,
then shocked quartz, the most important and unequivocal evidence
of
terrestrial impact, should be preserved in strata of the
appropriate
time interval. Quartz-bearing rocks below the North Mountain
Basalt
display in thin section up to five different sets of subparallel,
subplanar features, which contain numerous tiny voids causing the
optical contrast. Within error limits, universal-stage
measurements
reveal that the features seem to be oriented parallel to
rhombohedral
planes, which would favour their shock origin. Transmitted
electron
microscopic observations of the same grains show, however, that
the
optically visible features are subgrain boundaries. Many perfect
dislocations present in the quartz grains clearly indicate
tectonic
origin. This microstructure is distinctly different from that of
shocked quartz, which is free of dislocations and contains
amorphous
silica lamellae, the so-called planar deformation features. A
catastrophic impact event at the Triassic-Jurassic boundary,
however,
cannot be excluded, because this boundary has not yet been
comprehensively investigated. Copyright 1998, Institute for
Scientific Information Inc.
=================
(7) TO BE OR NOT TO BE: THE PHILOSOPHY OF EXTINCTION
G.M. Aitken: Extinction. BIOLOGY & PHILOSOPHY, 1998, Vol.13,
No.3,
pp.393-411
UNIVERSITY OF LANCASTER, DEPT PHILOSOPHY, LANCASTER LA1 4YW,
ENGLAND
A significant proportion of conservationists' work is directed
towards efforts to save disappearing species. This relies upon
the
belief that species extinction is undesirable. When
justifications
are offered for this belief, they very often rest upon the
assumption
that extinction brought about by humans is different in kind from
other forms of extinction. This paper examines this assumption
and
reveals that there is indeed good reason to suppose current
anthropogenic extinctions to be different in kind from
extinctions
brought about at other times or by other factors. Having
considered -
and rejected - quantity and rate of extinction as useful
distinguishing factors, four alternative arguments are offered,
each
identifying a way in which anthropogenic extinction is
significantly
different from other forms of extinction, even mass extinction:
(1)
Humans are a different kind of natural cause from other causes of
extinction; (2) Extinctions brought about by humans are uniquely
persistent; (3) Anthropogenic extinctions are effectively random
whereas past mass extinctions are rule-bound; (4) The impact of
the
current anthropogenic extinction event differs from the impact of
other extinction events of the past, such that future recovery
may
not follow past patterns. Together, these four arguments suggest
that
the present-day extinction event brought about by humans may be
unprecedented and that we cannot clearly extrapolate from past to
present recovery from extinctions. Although insufficient as
justification for the claim that present-day extinctions are
undesirable, the arguments provide some ammunition for
conservationists' conviction that species extinction - in which
humans play an accelerating role - ought to be prevented.
Copyright
1998, Institute for Scientific Information Inc.
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