PLEASE NOTE:
*
CCNet 104/2001 - 1 October 2001
===============================
"It's a bit disappointing that [the NEO Centre] appears to
be a shop
window without any commitment, so far, to spending on the
necessary
research. The NEO centre that was envisaged in the report from
the
task force is not what is being offered. The task force saw it
being
solidly based in a research centre, with the provision of public
information
as an important but secondary function. A quarter of a million
pounds has
been thrown into a public-understanding-of-science exercise which
won't necessarily be linked to an authoritative voice."
--Jacqueline Mitton, The Times, 1 October 2001
"On the whole, the reaction of the Government to our
recommendations
is a move very much in the right direction. But it's clear that
the story
is not yet complete, so I await with interest further progress
over the
rest of this year."
--Harry Atkinson, Chairman of the UK Task Force on NEOs
"Archaeologists have found evidence that appears to support
the
theory that a catastrophic flood struck the Black Sea region more
than
7,000 years ago, turning the sea saline, submerging surrounding
plains and possibly inspiring the flood legends of Mesopotamia
and the
Bible. In their first scientific report, the expedition leaders
said that a
sonar survey in the sea off Sinop, a city on the northern coast
of Turkey,
conducted in the summer of 2000, revealed the first distinct
traces
of the preflood shoreline, now about 500 feet underwater. At one
site, the sonar detected more than 30 stone blocks on a gently
sloping but
otherwise featureless bottom. Further investigation with remote
controlled
cameras revealed pieces of wood and other objects, possibly
ceramics.
--John Noble Wilford, The New York Times, 1 October 2001
(1) ASTEROIDS? WHAT ASTEROIDS?
The Times, 1 October 2001
(2) SCHOLARS FIND FURTHER SIGNS OF BIG FLOOD EVOKING NOAH
The New York Times, 1 October 2001
(3) P/TR SCIENCE AND K/T FOLLOW-UP
Hermann Burchard <burchar@mail.math.okstate.edu>
(4) AN EXTRATERRESTRIAL IMPACT AT THE PERMIAN-TRIASSIC BOUNDARY?
Science, Volume 293, Number 5539, Issue of 28
Sep 2001, p. 2343.
(5) NASA PREPARING FOR BIGGEST METEOR STORM IN 35 YEARS
Florida Today, 29 September 2001
(6) BORRELLY, THE UNIVERSE & EVERYTHING
NearEarth.net, 28 September 2001
(7) OLDEST ASIAN TOOLS SHOW EARLY HUMAN TOLERANCE OF VARIABLE
CLIMATE
National Geographic News, 26 September 2001
(8) AND FINALLY: IF LIFE EXISTS ON MARS, OUR ROBOTIC PROBES MAY
HAVE BROUGHT
IT THERE
Space Daily, 1 October 2001
================
(1) ASTEROIDS? WHAT ASTEROIDS?
>From The Times, 1 October 2001
http://www.thetimes.co.uk/article/0,,74-2001340034,00.html
BY ANJANA AHUJA
A government plan to set up a body to monitor Near Earth Objects
is being
dismissed by experts in the field as a shop window with nothing
on the
shelves.
Scientists are chillingly clear about what would happen if a
sizeable
asteroid or comet hit Earth. "You are talking about
Hiroshima on a worldwide
scale," says Dr Duncan Steel, an astronomer at Salford
University who has
warned repeatedly of the apocalyptic consequences of ignoring
such a
scenario.
To address these concerns - and perhaps to assuage an anxious
public whose
fears had been stoked by such films as Deep Impact and Armageddon
- a task
force on Near Earth Objects (NEOs) was convened last year by the
Government.
There are currently 258 potentially hazardous objects, defined as
bodies at
least 150m long whose orbits bring them to within 7.5 million km
of the
Earth (20 times the distance between the Earth and the Moon).
Last month
Lord Sainsbury of Turville, the science minister, invited
organisations to
bid to host an information centre dedicated to NEOs.
Between Lord Sainsbury's announcement and today, which is the
deadline for
bids to be submitted to the British National Space Centre (BNSC)
in London,
a quiet dismay has sprung up in the research community. Academics
suspect
that, instead of being an authoritative body that will join the
international scientific effort to track asteroids and comets,
the NEO
Information Centre is little more than a glorified PR exercise
which will
perform the admirable but unscientific task of running a website
and
producing information packs.
"It's a bit disappointing that this (the centre) appears to
be a shop window
without any commitment, so far, to spending on the necessary
research," says
Dr Jacqueline Mitton, an astronomer. "The NEO centre that
was envisaged in
the report from the task force is not what is being offered. The
task force
saw it being solidly based in a research centre, with the
provision of
public information as an important but secondary function. A
quarter of a
million pounds has been thrown into a
public-understanding-of-science
exercise which won't necessarily be linked to an authoritative
voice."
Whoever succeeds in winning the £250,000 contract will have to
accept
restrictions on what it can say in public. The BNSC's website
says: "The
contractor will accept some limitations on its
freedom to promote views on UK space policy, and particularly on
the hazard
presented by NEOs." Mitton says that this "raises
suspicions" among
scientists, who cherish their right to discuss and publish
information
freely. She asks: "Is this centre going to be a truly
independent body that
people can trust, or just a mouthpiece for government policy?
Mitton says
that her views are personal, not those of the Royal Astronomical
Society,
for whom she is a press officer. However, it is likely that they
are shared
by a large proportion of scientists.
It is some consolation, she says, that the Particle Physics and
Astronomy
Research Council (PPARC) has commissioned a review of the UK's
international
telescope facilities. There are also ongoing negotiations with
international bodies
such as the European Space Agency and Nasa, so there is hope that
Britain may
yet join in the tracking effort.
A BNSC spokesman defended the centre, saying it was only one of a
four-point
package. He added that the PPARC review would address the issue
of research,
although no funds had yet been committed to it.
Steel says that there is a one-in-100,000 risk of an asteroid 1km
long
hitting Earth in any year. The effect would be a global
catastrophe, he
says, wiping out up to half the world's population. "It
wouldn't matter where it hit,"
he adds. "It would be the equivalent of unleashing 100,000
megatonnes of TNT,
more than a thousand times worse than any nuclear weapon that has
been
tested." Those within 100 miles of the impact would be
vaporised. An ocean
impact offers no salvation - the resulting tsunami would drown
millions.
Even if an asteroid or comet hit Antarctica, at least a quarter
of Britons
would perish in the resulting shroud of toxic gases.
Steel says that Britain is paying too little attention to
tracking NEOs: "We
find objects and lose them again. It's like finding a needle in a
haystack,
then tossing it back. The UK has a suite of astronomical
facilities around
the world that could make an invaluable contribution to the
international
monitoring effort."
Steel refuses to be drawn on whether the NEO information centre
is likely to
be a disappointment, but his dissatisfaction is evident. He says:
"I have
been unable to obtain funds to do research in this area. In
Europe the
leading countries in tracking NEOs are Italy, Germany, France and
Spain.
They view the posturing that's happening here as a farce."
By coincidence, today also sees the opening of the Spaceguard
Centre in
mid-Wales, a public information centre on NEOs set up by
Spaceguard UK, a
private group that has lobbied for NEO tracking. Jay Tate, the
director of the
centre, has been a vociferous critic of what he sees as a lax
British attitude to
the threat from NEOs. He has submitted a bid to run the NEO
Information Centre. Tate explains: "My concern is that the
centre would be a
very smart shop window, but there would be nothing on the
shelves. The only
way you can tackle it is by running the shop window."
The £250,000 on offer would not be enough to set up a research
programme, he
admits, but he says that if he is successful he would try to
influence the
BNSC to go further and instigate a proper research programme.
Tate is also bullish
about what he sees as a "gag clause" in the contract:
"They can't gag you on matters
of fact." He adds that, if he could not speak out, there
would be
plenty of agitators outside the BNSC who would step into his
shoes and
"rattle the cages".
Dr Harry Atkinson, who chaired the task force, was tactful when
asked
whether the NEO information centre fell short of expectations.
Atkinson, a
former chairman of the European Space Agency's council, said:
"On the whole,
the reaction of the Government to our recommendations is a move
very much in
the right direction. But it's clear that the story is not yet
complete, so I
await with interest further progress over the rest of this
year."
During which, an observer might note, 13 asteroids and comets are
expected
to make close approaches to Earth.
Copyright 2001, The Times
============
(2) SCHOLARS FIND FURTHER SIGNS OF BIG FLOOD EVOKING NOAH
>From The New York Times, 1 October 2001
http://www.nytimes.com/2001/10/01/science/social/01FLOO.html
By JOHN NOBLE WILFORD
Archaeologists have found evidence that appears to support the
theory that a
catastrophic flood struck the Black Sea region more than 7,000
years ago,
turning the sea saline, submerging surrounding plains and
possibly inspiring
the flood legends of Mesopotamia and the Bible.
In their first scientific report, the expedition leaders said
that a sonar
survey in the sea off Sinop, a city on the northern coast of
Turkey,
conducted in the summer of 2000, revealed the first distinct
traces of the
preflood shoreline, now about 500 feet underwater.
At one site, the sonar detected more than 30 stone blocks on a
gently
sloping but otherwise featureless bottom. Further investigation
with remote
controlled cameras revealed pieces of wood and other objects,
possibly
ceramics.
The site "appeared uniquely rectangular" in the sonar
image, and the stone
blocks did not appear to be part of a natural geological
formation,
expedition scientists reported in today's issue of The American
Journal of
Archaeology. Analysis of core samples yielded chemical evidence
that
archaeologists said were consistent with the interpretation that
the site
was once occupied by people.
"The expedition clearly has found a subaquatic landscape
with materials that
belong to the period before the inundation," said Dr. Bruce
Hitchner, an
archaeologist at the University of Dayton, Ohio, and editor of
the journal,
a publication of the Archaeological Institute of America.
"They have
confirmed an important element of the flood theory, quite
convincingly I
think."
The expedition was led by Dr. Robert D. Ballard, an oceanographer
and
president of the Institute for Exploration in Mystic, Conn., and
Dr. Fredrik
T. Hiebert, an archaeologist at the University of Pennsylvania.
The research
was supported in part by the National Geographic Society.
Among the expedition's most striking discoveries were four Roman
and
Byzantine shipwrecks, several of them surprisingly well preserved
because of
the oxygen-deficient waters at the bottom of the sea.
Copyright 2001, The New York Times
==============
(3) P/TR SCIENCE AND K/T FOLLOW-UP
>From Hermann Burchard <burchar@mail.math.okstate.edu>
Dear Benny,
Iain Gilmour in CCNet 2001/9/28 (11) LACK OF IMPACT-DERIVED
HELIUM-3 AT P/T
BOUNDARY CASTS DOUBT ON IMPACT THEORY refers to an item that is
actually a
joint article in three parts,
An Extraterrestrial Impact at the Permian-Triassic Boundary?
by K. A. Farley, S. Mukhopadhyay Yukio Isozaki, Luann Becker, and
Robert J.
Poreda, Science Sep 28 2001: 2343
http://www.sciencemag.org/cgi/content/full/293/5539/2343a
The initial report was by L. Becker, R. J. Poreda, A. G.
Hunt, T. E. Bunch,
M. Rampino, Science 291, 1530 (2001), of extraterrestrial
helium-3 trapped
in cosmogenic fullerene molecule cages found in the P/Tr boundary
strata of
Chinese and Japanese rocks. See earlier CCNet coverage
March 2 (Taylor,
Peiser), March 5 (Glikson, Gilmour) and March 13, 2001
(Grondine).
In the first part of the September 28 paper Farley and
Mukhopadhay report,
as emphasized by Iain Gilmour, that there is no helium-3 anomaly
exhibited
by their samples. In the second part, Isozaki objects to
the Japanese
strata as being in the wrong place, below the PTB. Both
objections are
refuted in the third part by Becker and Poreda.
That third part appears to be good science, answering criticisms
sure-footedly, quite detailed and reliable, at least to this
amateur.
Specifically, Becker-Poreda explain that the samples in the two
studies were
essentially extracted from different strata, or more precisely,
by different
treatments of subunits of Meishan Bed 25, with only their own
original
treatment doing justice to the extinction layer.
Hence, Gilmour's truism "if your experiment is not
reproducible then what
you are doing is not science" would seem to be malapropos.
By way of comparison, he also refers to the K/T boundary (KTB)
and to the
more perfect state of its science. This gives me an excuse to
remark on
unfinished business regarding K/T. Work by a University of Texas
team of
geologists implies that the Chicxulub impact (which is now tied
by almost
everybody to the KTB) penetrated the crust of the Earth and
affected the
mantle underneath the crater, Earth's rocky and fairly solid
interior shell.
Quoting in part from their press release:
"The impact was so enormous it changed the shape of the
earth's
crust -- 22 miles below the surface of the planet. The Chicxulub
crater
is the first location where deformation at the base of the crust
has been
found in a terrestrial impact crater. The scientific team
concluded
that the Chicxulub crater is about 125 miles in diameter, and
that 12,000
cubic miles of debris was blasted out of the earth by the impact.
The
impact carved out a cavity about 7.5 miles below sea
level..."
"Additional analysis of the OBS data revealed that a region
at the
center of the crater about 22 miles in diameter has been uplifted
by
about 11 miles as a result of the impact and removal of overlying
material." (December 15, 2000)
Contact: Mary Lenz, Office of Public Affairs latest news from UT
Office of
Public Affairs P O Box Z Austin, Texas 78713-7509 (512) 471-3151
FAX (512)
471-5812
http://www.utexas.edu/admin/opa/news/00newsreleases/nr_200012/nr_crater001215.html
Plate tectonic motion, in the intervening time, has shifted the
North
American crust toward the West relative to the mantle. The site
of the
impact in the crust is in the Yucatan, but where was that at the
KTB epoch?
Maps of the age of the seafloor indicate an age of about 65 Ma
near the Lesser Antilles, with older crust to the West, but it is
not easy
to draw any inferences from this. It would be interesting to
trace the
original mantle spot where the impact occurred to see what
happened along
the way! The Greater Antilles island chain conveniently
lines up along or
near a path that was taken by the Chicxulub crater as the plate
shifted
westward.
Shortly after the Chicxulub impact a resurgent caldera must have
begun to
exist, a type of volcano known from other examples. It
first extruded the
Yucatan basement, then after an interval Cuba, with the magma
volume
lessening as the island tapers from West to East, and then the
remaining
islands of the Greater Antilles chain, with ever weakening
eruptions. The
plate continued to move west during this time with the caldera
remaining
fixed in the mantle, as is usual (the implied gradation in age of
the island
basement rocks should be verifiable).
The youngest of the Greater Antilles would be the Eastern-most
one, Virgin
Gorda, a tiny 12 km island that may have broken through the crust
fairly
recently. Its distance from the Yucatan along the island
chain is about
right for an average rate of plate motion. Reportedly
Virgin Gorda is
limestone upon a volcanic basement, as are presumably all of the
Greater
Antilles.
Regards,
Hermann
===============
(4) AN EXTRATERRESTRIAL IMPACT AT THE PERMIAN-TRIASSIC BOUNDARY?
>From Science, Volume 293, Number 5539, Issue of 28 Sep 2001,
p. 2343.
An Extraterrestrial Impact at the Permian-Triassic Boundary?
Becker et al. (1) presented geochemical evidence
that suggests that
the largest mass extinction in Earth history, at the
Permian-Triassic
boundary (PTB) 250 million years ago (Ma), coincided
with an
extraterrestrial impact comparable in size to the
one that likely
caused the end-Cretaceous extinctions 65 Ma (2).
Although Becker et
al. analyzed material from sections in Hungary,
Japan, and China, the
Hungarian section yielded no extraterrestrial
signature, and their
identification of the PTB in the Japanese section is
questioned in the
accompanying comment by Isozaki (below). Thus, only
their analyses of
the Chinese section provide hitherto uncontested
evidence for an
impact at the boundary--in the form of data on the
abundance and
composition of fullerenes in the "boundary
clay," a volcanic ash layer
called Bed 25 at Meishan, China (3). Although
fullerenes may be purely
terrestrial [see, e.g., (4)], Becker et al. report
that the fullerenes
from the Meishan ash carry extraterrestrial noble
gases in the cage
structure, rich in 3He and with distinctive 3He/36Ar
and 40Ar/36Ar
ratios, and that this signature therefore derived
from a bolide
impact. Here, we report that we are able to detect
fullerene-hosted
extraterrestrial 3He neither in aliquots of the same
Meishan material
analyzed by Becker et al., nor any in samples of a
second Chinese PTB
section, and that we thus find no evidence for an
impact.
Becker et al. reported helium in bulk rock and in
fullerenes extracted
from Meishan Bed 25 following acid demineralization.
Their two
aliquots of bulk rock yielded 0.43 and 0.58 pcc/g
(10 - 12 cc g - 1 at
standard temperature and pressure) of 3He. From 40 g
of rock, Becker
et al. extracted 14 µg of fullerene that yielded
very high 3He
concentrations, implying that fullerene-hosted
helium accounted for at
least 0.052 pcc/g of the 3He in Bed 25; this number
could be higher,
because Becker et al. provided no indication of
fullerene extraction
efficiency.
We first analyzed 15 aliquots of bulk rock from Bed
25, provided by
S. Bowring to be representative of the material he
supplied to Becker
et al. Samples were initially dried in an oven for 2
hours at ~90 to
100 °C to drive off adsorbed water. Based on
stepped-heating results
on fullerenes (1), no 3He would have been lost
during sample drying.
We then gently powdered 150 g of rock by hand with a
mortar and pestle
and thoroughly homogenized the sample. Ten aliquots
(~350 mg each)
were drawn from this homogenized powder; the
remaining five aliquots
were taken from several different clumps of the
material to assess
spatial heterogeneity. Samples were fused under
vacuum at 1400°C
following procedures reported earlier (5), except
that the acetic acid
step, designed to remove CaCO3, was not used on
these carbonate-poor
rocks. None of these samples yielded a significant
amount of 3He (Fig.
1): The mean of the 15 runs was 0.005 pcc/g, and the
maximum for any
single aliquot was only 0.01 pcc/g. We obtained
similar results from
six samples of the stratigraphically equivalent bed
at Shangsi, China
(also provided by Bowring). Hence, we obtained 3He
concentrations from
bulk rock samples that were a factor of 45 to 150
lower than those
reported by Becker et al. To ensure that we were
quantitatively
extracting all the He at 1400°C, we outgassed a
single sample at
1800°C after fusion at 1400°C; no additional 3He
was released.
Fig. 1. He isotope data for Chinese PTB samples.
Filled symbols, Becker et al. (1); open symbols,
this study.
We then demineralized a 16 g aliquot of Meishan Bed
25, following the
same HF-BF3 digestion procedure (6) used by Becker
et al. This residue
contained only 0.003 pcc of 3He per gram of starting
material. Because
the demineralized residue does not contain
significant 3He,
fullerene-hosted 3He within this residue cannot be
significant either,
so we did not isolate fullerene for noble gas
analysis. This
experiment places an upper limit on the
fullerene-hosted 3He in Bed
25 that is a factor of 15 lower than the
concentration reported by
Becker et al. (1).
The helium we obtained from Bed 25 samples is
reasonable for a
250-million-year-old volcanic ash bed. Large
inter-aliquot variability
in 4He content and the survival of most 4He through
HF
demineralization (Fig. 1) suggest that accessory
zircons, known to
exist in Bed 25 (3), control the distribution of
this isotope. The 3He
concentration and 3He/4He ratio (average <0.003
RA) of Bed 25 are
lower than we obtained from several hundred deep-sea
carbonate
sediments [see, e.g., (5)] and are at the low end of
the range
expected for purely terrestrial radioactive decay
processes (7). The
dearth of 3He from interplanetary dust particles
(IDPs)--not to be
confused with a fullerene-hosted impact
signature--is not surprising,
because Bed 25 is a volcanic ash and was likely
deposited quickly.
We thus find no evidence for the impact-derived 3He
reported by Becker
et al. Our analytical technique for 3He is as
sensitive and precise
[see details in (5)] as that used by Becker et al.,
so the discrepancy
between our results and theirs is probably not
analytical in origin.
Sample heterogeneity is also an unlikely
explanation: Although Becker
et al. found substantial 3He in all three aliquots
they analyzed (a
total of 41 g of rock), we were unsuccessful in
detecting
extraterrestrial 3He in any of our 22 aliquots (150
g of homogenized
Bed 25 in 10 aliquots, 1.5 g of spatially
distributed spot samples in
five aliquots, and 16 g of demineralized rock in one
aliquot from
Meshian, as well as 2 g of rock in six aliquots from
three samples of
the Shangsi P-Tr boundary bed).
Without confirmation of fullerene-hosted 3He in Bed
25, both the
occurrence of an extraterrestrial impact and the
cause of the mass
extinction at the PTB must remain open questions.
K. A. Farley
S. Mukhopadhyay
Division of Geological and
Planetary Sciences
MS 170-25
California Institute of Technology
Pasadena, CA 91125, USA
E-mail: farley@gps.caltech.edu
REFERENCES
1. L. Becker, R. J. Poreda, A. G. Hunt, T. E. Bunch,
M. Rampino,
Science 291, 1530 (2001).
2. L. W. Alvarez, W. Alvarez, F. Asaro, H. V.
Michel, Science 208,
1095 (1980).
3. S. A. Bowring et al., Science 280, 1039 (1998).
4. D. Heymann et al., Geol. Soc. Am. Spec. Pap. 307,
453 (1996).
5. S. Mukhopadhyay, K. Farley, A. A. Montanari,
Geochim. Cosmochim.
Acta 65, 653 (2001).
6. T. L. Robl and B. H. Davis, Org. Geochem. 20, 249
(1993).
7. J. N. Andrews, Chem. Geol. 49, 339 (1985).
27 April 2001; accepted 17 August 2001
Becker et al. (1) reported an anomaly in 3He trapped
in fullerene from
PTB rocks from Japan and China, which in turn
suggested a possible
extraterrestrial impact as the cause of the PTB mass
extinction.
Although the approach of using the 3He signature
appears promising,
the stratigraphy of the Sasayama section in Japan
poses a major
problem that is fatal to their conclusion: The PTB
horizon is missing
in this section, and the "3He-enriched"
sample they analyzed has
actually come from at least 0.8 m (and possibly much
further) below
the PTB.
Owing to absence of good index fossils, the Sasayama
section is dated
by correlation with other sections. The PTB sections
of deep-sea chert
facies have been examined in more than ten sections
in Japan (2, 3);
all showed a constant lithostratigraphy that
comprised, from bottom to
top, (i) Late Permian bedded chert, (ii) latest
Permian siliceous
claystone or shale, (iii) boundary black organic
claystone, (iv) Early
Triassic siliceous claystone, and (v) late Early to
Middle Triassic
bedded chert. The lower chert and siliceous
claystone are
characterized by Chanhsingian (late Late Permian)
radiolarians such as
Neoalbaillella optima and Albaillella triangularis
(4), and the upper
siliceous claystone and chert contain distinct Early
Triassic forms.
The central black claystone, less than 5 m thick,
yields only
ill-preserved microfossils and thus is not dated
precisely.
Nevertheless, these data indicate that the PTB
horizon is somewhere
within the black claystone (2), not in the lower
siliceous claystone.
Thus the "3He-enriched" sample of Becker
et al. (1) was clearly
collected from the Late Permian interval at least
0.8 m below the PTB.
Making the situation worse, this section is cut in
the middle by a
fault, with gouge and chert breccia [described as
sheared black shale
in figure 2 of (1)] that has removed beds nearly 20
to 30 m thick
between the lower siliceous claystone and the upper
chert. Thus, not
only does the section lack the PTB horizon, but this
faulting has
removed an additional, undetermined interval of time
between the
claimed "3He-enriched" sample and the PTB.
In any case, the Permian
radiolarians and conodonts survived even above this
"3He-enriched"
horizon up to the top of the siliceous claystone.
This suggests that
the alleged impact event did not terminate such
cosmopolitan marine
biota that flourished throughout the Permian and
finally disappeared
at PTB.
At least for confirming the background absence of
3He in adjacent
horizons immediately above and below PTB, Becker et
al. should have
checked better PTB sections and used more samples
collected following
a double-blind protocol. Becker et al. also reported
a similar 3He
spike from Bed 25 (a volcanic tuff of terrestrial
origin) immediately
below PTB in the Meishan section in China. Because
the "3He-enriched"
sample from Sasayama is significantly older than
Meishan Bed 25, they
cannot have been from the same impact event.
Yukio Isozaki
Department of Earth Science and Astronomy
University of Tokyo
Komaba, Tokyo 153-8902, Japan
REFERENCES
1. L. Becker, R. J. Poreda, A. G. Hunt, T. E. Bunch,
M. Rampino,
Science 291, 1530 (2001).
2. Y. Isozaki, Science 276, 235 (1997).
3. Y. Kakuwa, Palaeogeogr. Palaeoclimatol.
Palaeoecol. 121, 35 (1996).
4. K. Kuwahara, S. Nakae, A. Yao, J. Geol. Soc.
Japan 97, 1005 (1991).
2 April 2001; accepted 17 August 2001
Response: In our study (1), we suggested that an
impact event occurred
at the 250-million-year-old PTB, triggering the most
severe mass
extinction in the history of life on Earth. By
exploiting the unique
ability of the fullerene molecule to trap noble
gases inside of its
caged structure, we were able to determine whether
the origin of the
fullerenes was extraterrestrial (ET) or terrestrial.
We have found
fullerenes with ET helium associated with extinction
events in five
locations at the 65-million-year-old
Cretaceous-Tertiary boundary
(KTB) and in two locations at the PTB (1, 2).
Although it has been
suggested that the fullerenes isolated from some KTB
sediments may
have been associated with terrestrial
causes--specifically, with
global wildfires triggered by the impact event--it
has now been
accepted that the KTB fullerenes are
extraterrestrial, delivered
exogenously to the Earth during the impact itself
(3, 4).
Farley and Mukhopadhyay, at Caltech, report that
they have measured
background levels of 3He across the PTB in sections
in Meishan and
Shangsi, China, and have concluded that there is no
evidence for the
delivery of ET material to the Earth by a bolide.
Rather, their
results are consistent with helium present in a
250-million-year-old
ash layer found at both boundary sections. We
observed significant
differences between the procedures we used and those
carried out
during their study, however, and we believe that
these differences
influenced the outcome of their experiments.
In our study, we obtained a ~75-g sample of Bed 25
from S. Bowring
that contained the base of this unit, which
represents the time
interval during which more than 90% of all marine
organisms, most of
the terrestrial vertebrates, and many plants were
brought to an abrupt
extinction (1, 5, 6). Because we were interested in
focusing on this
discrete event rather than looking at the continuous
flux of 3He
throughout Bed 25, we separated out the carbon-rich
basal material,
characterized by an interstratified reddish-gray
montmorillonite-illite clay layer. This reduced our
bulk sample to the
~40 g of material that was demineralized using the
procedures outlined
in (1). The acid residue (442 mg) that represented
about 1% of the
original material was extracted with solvents to
isolate the fullerene
component (14 µg). In contrast, the Bed 25 ash,
provided to us by the
Caltech group, contained less than 0.1% (or 6 mg in
7 g of ash)
acid-resistant residue, and that fraction appeared
to be mostly
resistant silicates such as zircon. Thus, our
contention is that the
Caltech sample contained neither the organic carbon
carrier for the
3He-rich fullerene component nor the carrier
(whatever it may be) for
the bulk 3He or background flux. Our bulk 3He
concentrations in two
aliquots of the PTB sample yielded values of 0.43
and 0.58 pcc/g,
while several samples above and below the boundary
had 3He
concentrations about 10 times lower ( <=
0.02 to 0.2 pcc/g) (7).
To further assess the variability in bulk 3He
measured for the Meishan
samples collected at the boundary (Bed 25) and in
samples directly
above and below this interval, we also obtained a
separate suite of
Meishan samples from S. D'Hondt. The samples
collected by D'Hondt were
evaluated for delta 13C and compared to replicate
samples measured in
(5). This material also represented the changes in
lithology at the
base of Bed 25 and in the sediments above and below.
These samples had
even more 4He (3 to 10 µcc/g) than the samples
measured in either our
study (1) or that of Farley and Mukhopadhyay. In our
case, the high
4He concentrations made it impossible to evaluate
the 3He
concentrations because the 3He/4He ratio was at the
abundance
sensitivity limit. Unfortunately, our samples were
not available for
reassessment of the bulk 3He upon submission of the
comment by Farley
and Mukhopadhyay. We have since reproduced our own
results with four
replicate analyses of the boundary layer. The 3He
concentrations at
the Meishan boundary range from 0.15 to 0.5 pcc/g.
We will also
provide our samples to two separate labs for
independent measurements
of the bulk 3He. We are confident that these labs
will reproduce our
results (1) and will further demonstrate the
differences in the
samples provided by S. Bowring to Caltech and us.
The differences in bulk 3He and 3He fullerene
concentrations appear to
be directly attributable to sample selection and
preparation. By
homogenizing a 150-g sample of volcanic ash, Farley
and Mukhopadhyay
may reduce the variability and noise in the 3He
signature, an
important consideration when examining long-term IDP
flux signals. We
concur with their conclusion that the volcanic ash
would have been
deposited very rapidly and would not preserve the
extraterrestrial
signature attributed to IDPs. However, when
examining "event markers"
such as fallout from a bolide impact, the
homogenization strategy
would severely dilute the already weak 3He signal
present in the bulk
ash. Variations in the carbon content and 3He
concentrations in the
Bed 25 samples clearly point to the fact that the
two groups examined
very different samples. The change in lithology at
the base of Bed
25 apparently makes a significant difference in the
identification of
the bolide event marker, and care must be taken to
identify and
quantify the helium carriers present in the
boundary.
In a separate comment, Isozaki suggests that the
fullerenes we
detected in the siliceous claystone at Sasayama did
not come from the
PTB. Instead, using lithostratigraphy, he places the
true boundary
somewhere within the carbonaceous claystone above
this interval.
However, as pointed out both by Kakuwa (8) and in
Isozaki's comment,
the PTB cannot be precisely defined in any of the
Japanese sections
because of poor stratigraphic control. Moreover,
neither the siliceous
claystone nor the carbonaceous claystone have
age-diagnostic fossils
to properly date the boundary at Sasayama or in any
of the Japanese
sections (8), as the comment by Isozaki
acknowledges.
The principal difference underlying our placement of
the boundary
compared with that of Isozaki rests on the mechanism
that led to the
PTB mass extinction. Isozaki favors a model
involving overturn of
CO2-saturated deep anoxic water, coupled with a
hypothesized
"hypercapnia" that apparently lasted some
20 million years (9). As
pointed out by Gin et al. (5), however, the mass
extinction that
occurred at the PTB was abrupt, lasting only a few
100,000 years. Our
boundary sample, provided by M. Rampino, was
selected based upon
evidence for an extraterrestrial cause (10, 11). So
far, we have only
found fullerene at the boundary, and not in
significant concentrations
above and below (1, 2). Thus, in the absence of any
biostratigraphy
and poor stratigraphic control (8), we feel that the
best
interpretation for the boundary at Sasayama is in
the siliceous
claystone, where fullerene and other
extraterrestrial signatures have
been identified (1, 10, 11).
Perhaps the most significant drawback to our
investigation of the PTB
to date is the lack of geographic spread and the
inability to
demonstrate that other extraterrestrial signatures,
like those
reported in some KTB sites (1), are also present in
the PTB. New
results on sediments collected from the Meishan PTB
show that Fe-Si-Ni
grains are concentrated in the top 2 cm of Bed 24e
and in the
overlying basal portion of Bed 25 (12). These
Fe-Si-Ni grains are
produced at very high temperatures (Fe, 2890oC; Ni,
2863oC; Si,
2227 oC), and are thus inconsistent with a volcanic
origin but
consistent with impact-metamorphosed grains found in
some impact
craters and in sediments associated with the KTB
(12, 13).
Interestingly, some Fe-rich nuggets have also been
reported in the
siliceous claystone at Sasayama (14). Based on these
new results, it
would appear that an impact event of global
proportions remains the
best explanation for the most severe biotic crisis
in the history of
life on Earth.
Luann Becker
Department of Geological Sciences
Institute of Crustal Studies
University of California at Santa Barbara
Santa Barbara, CA 93106, USA
E-mail: lbecker@crustal.ucsb.edu
Robert J. Poreda
Department of Earth and
Environmental Sciences
University of Rochester
Rochester, NY 14627, USA
REFERENCES AND NOTES
1. L. Becker, R. J. Poreda. A. G. Hunt, T. E. Bunch,
M. Rampino,
Science 291, 1530 (2001).
2. L. Becker, R. J. Poreda, T. E. Bunch, Proc. Natl.
Acad. Sci. U.S.A.
97, 2979 (2000).
3. D. Heymann, L. P. F. Chibante, R. R. Brooks, W.
S. Wolbach, R. S.
Smalley, Science 256, 545 (1994).
4. P. J. F. Harris, R. D. Vis, D. Heymann, Earth
Planet. Sci. Lett.
183, 355 (2000).
5. Y. G. Gin, et al., Science 289, 432 (2000).
6. The boundary layer (Bed 25) provided by S.
Bowring was from a
collecting trip in 1996 and is the same material
that preserved the
carbonate isotopic excursion reported in (5). Our
sample contained a
thin layer of carbon-rich material in the basal
portion of Bed 25 (15)
and is consistent with our finding of fullerene (a
pure carbon
molecule). In contrast, the samples provided to
Farley and Mukhopadyay
were from a different collecting trip (1999) and
apparently did not
contain the carbonaceous layer found in samples
collected in 1996 (see
discussion in text).
7. These values should have been reported as
upper-limit
concentrations in our paper (1), because the VG5400
mass spectrometer
has an abundance sensitivity of 108 for helium. A
significant fraction
of the 3He signal for nonboundary samples at Meishan
is from the
low-energy tail of the 4He (the MAP 215-50 mass
spectrometer used by
Caltech does not have this limitation).
8. Y. Kakuwa, Palaeogeogr. Palaeoclimatol.
Palaeoecol. 121, 35 (1996).
9. A. H. Knoll, et al., Science 273, 452 (1996).
10. S. Miono, et al., Nucl. Instrum. Methods Phys.
Res. B109, 612
(1996).
11. S. Miono et al., Lunar Planet Sci. XXIX (1998)
(CD-ROM).
12. K. Kaiho, et al., Geology 29, 815 (2001).
13. Y. Miura, et al., Adv. Space Res. 25, 285
(2000).
14. S, Miono, Y. Nakayama and K. Hanamoto, Nucl.
Instrum. Methods
Phys. Res. B150, 516 (1999).
15. S. Bowring, D.H. Erwin, personal communication.
20 July 2001; accepted 12 September 2001
Volume 293, Number 5539, Issue of 28 Sep 2001, p.
2343.
Copyright © 2001 by The American Association for
the Advancement of
Science.
==============
(5) NASA PREPARING FOR BIGGEST METEOR STORM IN 35 YEARS
>From Florida Today, 29 September 2001
http://www.floridatoday.com/news/space/stories/2001b/sep/spa092901a.htm
By Kelly Young
FLORIDA TODAY
CAPE CANAVERAL - If satellites could duck and cover, Nov. 18
might be the
time to do it. That's when the worst meteor storm in 35 years is
expected to
hit. But from the ground, the storm will appear as beautiful
streaks of
light in the night sky, perhaps as many as 2,000 per hour.
Under dark skies on a normal night, it is possible to see four to
five
meteors an hour, said Bryan Craven, an officer at the Brevard
Astronomical
Society.
This year's Leonid meteor storm could be a treat for skywatchers,
but
there's a 1-in-1,000 chance that they could strike a satellite.
The tiny meteors, the size of dust or grains of sand, are left
over from the
tail of comet Tempel-Tuttle, which swings through the inner solar
system
every 33 years.
When the dust burns up in the atmosphere, it leaves a light
streak, or a
shooting star. In the early morning of Nov. 18, North American
skywatchers
may see dust left over from when the comet swung by Earth in the
18th
century.
The riskiest aspect of the meteors isn't their size, but their
potential for
shorting out a satellite, said Bill Cooke at NASA's Marshall
Space Flight
Center.
When a meteor zipping along at 40 miles per second hits an
object, it
creates a tiny cloud of ions, or charged particles. That charged
cloud could
interfere with a satellite's electronics, Cooke said.
This was the case in 1993 during the Perseid meteor shower when
the European
Space Agency's Olympus communications satellite lost control.
But many satellites probably will do nothing different. Turning a
camera or
other instruments off may do more harm than good.
"It's always risky doing things with satellites," said
Cooke, who analyzes
the threat meteors pose to satellites. "Once it's up there,
people like
leaving them up there and doing their thing."
Two of NASA's largest space assets, the Hubble Space Telescope
and Chandra
X-ray Observatory, will try to minimize damage by turning their
rear ends
into the incoming storm.
NASA never launches a shuttle during a meteor storm. But since
the Leonids
only will last a day or two, it probably won't affect the
scheduled Nov. 29
launch of space shuttle Endeavour. And the International Space
Station
should be safe because of its shielding, Cooke said.
The Leonids, called so because the meteors appear to come out of
the
constellation Leo the Lion, produce a meteor shower every year. A
meteor
shower typically means one meteor every minute or so. But a
meteor storm can
mean thousands of meteors an hour.
"It should be a pretty good show," said Bob Lunsford,
visual coordinator for
the American Meteor Society.
Copyright 2001, Florida Today
============
(6) BORRELLY, THE UNIVERSE & EVERYTHING
>From NearEarth.net, 28 September 2001
http://www.nearearth.net
from Joshua, NearEarth.net staff
As long as humans have been alive, breathing, and looking up at
the stars,
comets have been enigmas. Historically they have actually been
cast in a
negative light, most recently by being associated with the mass
suicide of
1997.
There are ancient records of comets, including sophisticated
charts
detailing cometary anatomy from China thousands of years ago. But
until
fairly recently, the western view of comets submitted to
Aristotle's
naturalistic philosophies, with no real, provable explanation of
what these
strangers in the sky were. Comets baffled our ancestors for
thousands of
years. In fact, the very word 'comet' ("hairy star")
implies a shroud, a
comatose kind of state, something mysterious which cannot be
penetrated or
fully understood.
Comets are really the only objects in the sky which are visible
from Earth
and don't follow a set path like the stars and planets. We can
begin to
imagine what it was like for our predecessors to walk out one
evening and
suddenly notice something in the sky that
just...shouldn't...be...there!
Little wonder that these ghostly objects -who appeared for no
reason and
vanished just as inexplicably- were feared by so many, for so
long.
The mind who provided the first great breakthrough in humankind's
understanding of comets, was, of course, Sir Edmund Halley's. His
incredible
achievements are beyond the scope of this article. But suffice it
to say
that Halley brought the comets to within our understanding by
working them
into the new layout being pioneered by his contemporary -and
friend- Isaac
Newton.
Arguably cometary science's second big breakthrough occurred
again during an
apparition of Halley's comet, this time in 1986. Comet Halley was
joined by
a small fleet of spacecraft, the most daring of which was Giotto,
launched
by the European Space Agency. Giotto captured a timeless image of
the
nucleus of Halley's Comet. It was, no doubt, a great milestone in
our
understanding of comets.
The images were not sharp, and not of high resolution. But they
clearly
revealed the dynamic nucleus with its active jets, and perhaps
they also
perpetuated the popular image of the comet as a rigid iceberg,
floating in
space.
Finally, on Saturday, September 22, the Deep Space One probe, a
collection
of some of the most advanced technologies to ever fly, defied all
odds and
captured stunning portraits of Comet Borrelly's tiny nucleus. The
engineering which enabled this feat is, again, beyond my scope,
but is well
worth investigation.
As DS1 and Borrelly raced past one another, DS1 took a series of
about 30
historic images. The most spectacular of these is a gorgeous
portrait of
Borrelly's sunlit side. Here we behold the very face of that
which so many
great ones have pursued. And it is more complex than most of us
expected. We
see areas that are black as chimney soot, lighter areas that
indeed resemble
ice, and chaotic interactions of all shades in between. There are
ridges and
hills, fault lines and valleys. The jets shoot out like geysers
from the
lightest areas on the object, which may show evidence of a
sediment of some
sort.
All in all, the comet is like nothing we have ever seen before! A
treasure
trove to the organic chemist, virgin territory to the explorer,
and maybe
the cosmic seed which led to each of us and all life on Earth.
After the images came in, Charles Morris of NASA's Comet
Observation Home
Page called it "really something special". Others
called it "remarkable",
and said this effectively doubles our knowledge of comets. Still
other have
called it "mind-boggling, and stupendous."
Personally, this is the one of the biggest events of my life.
This may be
hard to understand, but when you have been fascinated by these
objects all
your life, this is like opening King Tut's Tomb. Or better.
The only thing I can think to compare DS1 to -in terms of raw
significance-
happened within a fortnight of the flyby. I refer of course to
September 11,
2001.
It would be impossible to write an article about DS1 without
associating it
with September 11, 2001. That event also changed this world in an
instant..
Jeff Greenfield of CNN said that it will "take us some time
to find our legs
in this whole new world."
Deep Space 1 would certainly have received more publicity if not
for the
"epoch-making" events of September 11, 2001. One reason
I feel it is
important for people to appreciate DS1 is that the reconnaissance
we now
have of the structure of potentially hazardous comets may help us
tremendously at a future time, should the unthinkable occur. It
may seem
inconceivable, but the potential damage that a hazardous comet or
asteroid
promises would dwarf what happened in New York or
Washington.
The flyby was also the first world-class achievement on the part
of the
United States in the days following the events of September 11,
2001. The
United States is a nation for whom such great discoveries are the
norm, but
it was still terrific to have this accomplishment when we
did.
Perhaps Deep Space One should have been named
"Phoenix".
==========
(7) OLDEST ASIAN TOOLS SHOW EARLY HUMAN TOLERANCE OF VARIABLE
CLIMATE
>From National Geographic News, 26 September 2001
http://news.nationalgeographic.com/news/2001/09/0926_asiantools.html
by John Roach
When it's cold outside, modern humans don a sweater to ward off
the chill.
But how and when early humans began to develop an ability to cope
with
different climates has been a great puzzle in the study of human
evolution.The answer is important because it suggests when early
humans were
able to migrate out of tropical Africa and settle all corners of
the globe.
Now, researchers have determined that stone tools found in a
region of
northern China are 1.36 million years old, which provides direct
evidence of
the earliest human occupation of eastern Asia as far as 40
degrees north.
The stone tools were found in China's Nihewan Basin. During the
period when
they were used, 1.36 million years ago, much of the area was
covered by a
large lake that was ringed with forests of birch and elm trees.
Mammals such
as hippopotamuses, hyenas, rhinoceroses, and horses roamed the
area.
While the climate was probably humid and warm most of the time,
the area is
thought to have experienced bouts of cold and dry weather. To
settle in the
region, early humans would have had to adapt to this climate
fluctuation.
The stone tools are an indication of that early ability to thrive
in a
variable climate. They show that "early humans could live in
a wide range of
climate conditions," said one of the researchers, Rixiang
Zhu of the
Institute of Geology and Physics at the Chinese Academy of
Science in
Beijing. He and his collaborators published a report on their
findings in
the September 27 issue of Nature.
Magnetic Dating
The stone tools from the Nihewan Basin were found more than 20
years ago,
but until now their age was unknown. Anthropologists routinely
determine the
age of materials through a process known as isotopic dating, a
technique
based on knowledge about the rate of decay for certain
radioactive elements.
Dating the stone tools from the Nihewan Basin was a challenge
because they
lacked suitable material for isotopic analysis. Zhu and his
colleagues
overcame the hurdle by correlating the magnetic polarity of the
sediments in
which the tools were found with a known timeline of when Earth's
magnetic
field shifts its polarity, or attraction toward a specific
direction.
"We know that Earth's magnetic field flips polarity from
time to time, and
for the last several polarity reversals, the ages are rather
precisely
known," said Kenneth Hoffman, a paleomagnetist at California
Polytechnic
State University in San Luis Obispo and a co-author of the paper
in Nature.
"Sediments record the magnetic polarity of the field more or
less as they
are deposited," he explained.
The stone tools were found in a section of sediment that
correlates with a
known era of reverse polarity-when the needle in a compass would
have
pointed south instead of north-that lasted from 1.77 million
years ago to
1.07 million years ago.
Working under the assumption that the sediment was deposited at a
constant
rate, the researchers calculated that soils in which the stone
tools were
found were deposited 1.36 million years ago. Consequently, the
stone tools
must be 1.36 million years old.
"Any uncertainty to the result would come from the
assumption of a constant
rate of sedimentation during the reverse polarity period, yet
this
uncertainty is likely to be small," said Hoffman.
Evidence of Adaptability
The researchers do not know exactly how the early tools were
used. They
consist of several kinds of scrapers and sharp-edged tools, which
almost
certainly would have been used to cut meat off the bones of
mammals that
inhabited the region.
"That far north, we are dealing with changes in
daylight," said Richard
Potts, director of the Human Origins Program at the Smithsonian
Institution's National Museum of Natural History in Washington,
D.C., and
co-author of the scientific paper. "There would have been a
good growing
season and a season of relative dearth. Reliance on animal food
during
certain parts of the year may have been pretty important."
As corroborating evidence that early humans were able to thrive
in varied
climatic conditions over a million years ago, the researchers
point to
Lantian, an archaeological site on the Yellow River about 560
miles (900
kilometers) southwest of the Nihewan Basin. It was there that the
remains of
a 1.1 million year old Homo erectus were excavated in 1963.
Paleoclimatic evidence suggests that Lantian was a relatively
cold and windy
place 1.1 million years ago, said Potts.
"These two localities suggest that populations were able to
occupy or shift
their range over a considerable area, from Nihewan to the
southern margin of
the Loess Plateau, during a time of enhanced global and regional
climatic
variability that included intermittent aridification of north
China," the
researchers conclude in Nature.
Copyright 2001, National Geographic
===========
(8) AND FINALLY: IF LIFE EXISTS ON MARS, OUR ROBOTIC PROBES MAY
HAVE BROUGHT
IT THERE
>From Space Daily, 1 October 2001
http://www.spacedaily.com/news/life-01zg1.html
by Laura Woodmansee
Pasadena - Oct 1, 2001
The results of NASA's 1976 Viking lander missions were largely
inconclusive.
But, what if our spacecraft brought tiny forms of Earth life to
Mars? Could
it have survived there? If so, what does this mean for the future
exploration of Mars?
And there is Europa, probably the most likely source of
extra-terrestrial
life in our solar system. NASA has plans to send an orbiter and
then a
lander to search for signs of life in Europa's planet-wide ocean.
What is
being done to protect Europan life?
How can we seek out life in the solar system without harming it?
Can robotic
probes built on Earth be made clean enough to search for life on
other
planets without contaminating it? If we bring samples of alien
life back to
Earth, how do we prevent them from contaminating Earth's
biosphere?
"Planetary protection" is the prevention of "cross
contamination." That is,
preventing life from getting from one planet to another and
causing harm.
It's an important factor in space exploration that the public is
barely
aware of, but one that NASA spends a lot of time working on.
Dr. Karen Buxbaum, a supervisor of the Jet Propulsion Lab's (JPL)
Planetary
Protection Technologies Group says, "There's a certain
amount of
responsibility that we have as an agency that's doing exploration
to not be
sort of reckless in dumping stuff in other parts of the solar
system."
NASA divides planetary protection concerns into two categories;
forward and
backward contamination.
Backward contamination is the type of thing that books and movies
like H.G.
Wells' "War of the Worlds" and Michael Crichton's
"The Andromeda Strain"
have made popular. It is the contamination of Earth life by alien
spores,
microbes or organisms.
Science fiction has put the fear of contamination by alien life
in our
minds. But, what about the reverse? Could our space probes be
"infecting"
other worlds with Earth life?
It turns out that NASA is working to protect life on other worlds
from Earth
life, what the space agency calls forward contamination. Buxbaum
defines it
this way; "Forward contamination refers to contamination of
other solar
system bodies with biological material from the Earth." But,
this concern
for alien life remains largely unknown to the American public.
Should we care if we spread Earth life to other planets in our
solar system,
or anywhere else? NASA cares and that's why the agency has spent
over 30
(1967-2001) years and countless dollars trying to prevent cross
contamination.
Protecting life on other planets is important business for NASA.
It is
crucial to the exploration of the solar system. So much so that
NASA has
created an entire Planetary Protection branch. Dr. John Rummel,
NASA's
Planetary Protection Officer, works to protect life on Earth and
life
elsewhere based on NASA's planetary protection policy.
"The policy is actually based on the desire to preserve
extraterrestrial
environments for the science opportunities that are there,"
says Rummel.
In other words, if we bring Earth life with us to another planet,
there is
the chance that we may kill or harm indigenous life. Or, we may
make it
harder to determine if life ever existed there. We may mistake
Earth life
for alien life.
"It's in nobody's best interest to obscure that by
contamination with Earth
organisms," says Rummel. "Nor would you want to
discover a wonderful new
life form and know that you've killed it ... Essentially we can
meet ethical
considerations by the desire to preserve science."
Rummel must approve every NASA space probe before launch. "I
often imagine
myself strapped to a booster somewhere," Rummel says in a
comic voice,"
'Now, you won't launch this unless you get my signature.'"
The search for life beyond the Earth has lead to the new science
of
Astrobiology. Through a combination of many physical and life
sciences,
astrobiologists seek out life elsewhere in the solar system and
the
universe. It's important to know where life might be in order to
understand
where it must be protected. Scientists are only now starting to
understand
the so-called "habitable zone," the range of
environments where life can
exist.
Rummel ties astrobiology to planetary protection saying,
"The idea of
astrobiology ... [is] to study the origin, evolution, and
distribution of
life in the universe. And its extremely complementary on one
level with
planetary protection, in that by preserving the environments in
outer space,
you give yourself the potential to be able to discover more about
them."
On Earth, where there is water, there is life. But life doesn't
need water
to survive. In the past decade, scientists have discovered
"extremophiles",
organisms that live in the limits of the Earth's environment.
Scientists
have found life near hydrothermal vents at the bottom of the
ocean, deep
inside solid rock, and even at the core of nuclear reactors.
"One of the things that's changed in biology," Rummel
says, "Is we've found
life in extreme environments on Earth, that are completely
different from
anything you or I would be comfortable living in. Nevertheless,
there would
be ample opportunity to have life there. I don't want to live in
a boiling
pool in the middle of Yellowstone Park, but there are microbes
that just
love it."
Astronomers have found all the necessary ingredients for life
(water,
carbon, hydrogen, oxygen and nitrogen) inside clouds of gas and
dust
floating in deep space. At last count, our solar system has one
star, the
Sun, 9 planets with 68 moons, and thousands of comets and
asteroids. It's
quite possible that life arose in at least one of these places.
Detecting life is difficult, and scientists must be careful not
to confuse
Earth life with alien life. This would risk ruining future life
detection
experiments. Karen Buxbaum says, "Confusing the scientific
results is a
threat to the program."
In the near future, NASA plans to use astrobiology to search for
life on
Mars again. JPL scientist Dr. Roger Kern is planning for such a
mission.
"What we anticipate will happen with the first landers on
Mars is there will
be life detection experiments done in-situ, at the site,"
says Kern. "And
those experiments are probably not going to be looking for life,
per se, but
will be looking for molecules associated with life. So we want to
remove as
much [Earth life] as possible."
Kern continues, "Where as once NASA was only concerned with
sterilizing
spacecraft and making sure that the spacecraft couldn't shed a
live
organism, now we have an interest in seeing to it that it doesn't
shed a
dead organism as well ... it kind of takes you into a new
definition of
clean."
Even with super clean spacecraft, some microbes will always get
by. Dr.
Rummel says that the current planetary protection plan includes,
"An
inventory of organic constituents that might be delivered to
another body.
So that if you happen to go back there and find these things you
know that
you brought them."
In preparing a spacecraft for launch, technicians take samples of
any
microbes, spores, or cells on the spacecraft's surfaces. They
work to reduce
the number of contaminants to as low as possible, cleaning
several times if
needed.
Copyright 2001, SpaceDaily
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