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 g 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 1400C
   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 1400C, we outgassed a single sample at
   1800C after fusion at 1400C; 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 g). 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 cc/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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