PLEASE NOTE:
*
CCNet DIGEST, 23 March 1999
---------------------------
(1) SCIENTISTS DISCOVER NEW LIFE FORMS
Andrew Yee <ayee@nova.astro.utoronto.ca>
wrote:
(2) UPDATING IGNATIUS DONNELLY'S FANCIFUL CATASTROPHISM
Richard Meehan <meehan@stanford.edu>
(3) DYNAMICS OF EARTH-CROSSING ASTEROIDS: THE PROTECTED TORO
ORBITS
A. Milani*) & S. Baccili, UNIVERSITY OF
PISA
(4) ASTEROID MEAN ELEMENTS
A. Milani*) & Z. Knezevic, UNIVERSITY OF
PISA
(5) THE 1996 LEONID SHOWER AS STUDIED WITH A POTASSIUM LIDAR
J. Hoffner et al., LEIBNIZ INSTITUTE FOR
ATMOSPHERIC PHYSICS
(6) NEW RESEARCH ON THE PERMIAN-TRIASSIC BOUNDAY
S. Kershaw et al., BRUNEL UNIVERSITY
=========
(1) SCIENTISTS DISCOVER NEW LIFE FORMS
From Andrew Yee <ayee@nova.astro.utoronto.ca>
wrote:
University of Queensland
Brisbane, Australia
News release: 20 March 1999
UQ scientists discover new, tiny organisms
University of Queensland researchers have discovered novel
miniature
organisms which call into question the minimum size for life as
we know
it on Earth.
At 20 to 150 nanometres (billionths of a metre) in length, the
organisms, which they call nanobes, are much smaller than the
smallest
certified terrestrial bacteria ever found on the planet.
Researchers discovered the living colonies of organisms in
ancient
sandstones retrieved from an oil drilling site 3-5 km below the
Australian seabed. The finding has been reported in a recent
issue of
American Mineralogist.
The researchers behind the investigation are senior research
fellow Dr
Philippa Uwins and senior research officer Richard Webb of the
University's Centre for Microscopy and Microanalysis (CMM), and
PhD
student Anthony Taylor of the CMM and Microbiology and
Parasitology
Department.
They believe they may be the only research group in the world
with
actively growing nano-organisms.
While studying sandstone samples from exploration wells several
years
ago, Dr Uwins discovered strange filaments on the rocks.
"They were very small -- in the nano range, but we didn't
know what
they were," Dr Uwins said.
In unfunded research, and exercising their scientific curiosity,
they
performed numerous tests using state-of-the art ultra
high-resolution
scanning electron microscopy, transmission electron microscopy,
X-ray
spectroscopy and DNA staining.
The Lilliputian organisms were in the same size range but
distinctly
different from controversial fossil nanobacteria reported by NASA
scientists in a Martian meteorite in 1996 and by other scientists
in
various rock types on Earth.
Testing by the three Australian researchers has shown that the
nanobes
fulfil many criteria to qualify as biological life.
Their colonies grew spontaneously, they contained genetic
material
(DNA) and their chemical and biological structures were
consistent with
life. For example, they were composed of biological materials
such as
carbon, oxygen and nitrogen, and they were membrane-bound
structures
surrounding a possible cytoplasm and nuclear area.
In true scientific fashion, the scientists tried to disprove
themselves
by seeing if there could be another, plausible and non-biological
explanation for the nanobes.
They discounted many non-biological materials such as crystalline
minerals, carbonates, fullerenes, carbon nano-tubes and
non-living
polymers and concluded it was difficult to propose any known
non-biological materials which could account for the observed
structures.
Funding -- if only at a shoestring level -- was required to
advance the
project to the next level of investigation.
In December, the project received $19,000 Australian Research
Council
small grant support for further molecular and structural analyses
to
determine whether the organisms were related to bacteria or
fungi, or
belonged to a different evolutionary tree altogether.
"We will be the first group to perform DNA sequencing on a
new life
form with important and significant implications in many areas of
research including molecular and cell biology, earth planetary
sciences, environmental microbiology, medical microbiology,
biotechnology, chemical engineering and many others," Dr
Uwins said.
"If it is proven beyond doubt scientifically that such small
organisms
exist, it will be a major contribution to the controversial
debate
concerning extra-terrestrial life and the origin of life on Earth
and
other planets."
The debate was triggered in 1996 when NASA scientists in Houston
reported the existence of fossil nano-organisms in a 4.5
billion-year-old, potato-sized Martian meteorite which crashed to
Earth
in Antarctica about 13,000 years ago.
They suggested that the meteorite, known as ALH84001, showed
evidence
of extra-terrestrial ancient life on Mars. The egg-shaped
fossilised
objects observed in the Mars meteorite were 20 to 100 nanometres
long.
The announcement caused U.S. Vice-President Albert Gore and then
House
Speaker Newt Gingrich to agree on the need for more government
spending
and put Mars exploration on the front burner. One of the goals of
the
Mars exploration program now is to determine whether life started
on
Mars early in its history.
Critics of the NASA discovery argued that such nano life forms
were too
small to exist, because they had insufficient volume to contain
the
enzymatic and genetic material essential for life. They argued
that the
small size would not allow the supposed nanobacteria to contain
RNA and
a cell wall.
The same criticisms were levelled at a number of scientists,
including
geologist Dr Robert Folk of the University of Texas who in 1993
reported that they could see the fossilised forms of ultrasmall
microbes in many rocks and minerals found on Earth.
Dr Folk argued that nanobacteria may have escaped biologists'
notice
because they eluded the conventional tools used to study
bacteria.
He said that 200 nanometres was both the smallest size visible
with an
optical microscope, and the mesh size of the filters commonly
used by
microbiologists to strain out bacteria from liquids.
It became standard microbiological thought, he said, that because
no
bacteria smaller than 200 nanometres were seen, that none
existed. The
smallest known bacteria to date are mycoplasma, minute bacteria
which
cause a common form of pneumonia, and which can be as small as
200
nanometres.
Since their announcement, NASA scientists have searched for
living
nanobacteria on Earth.
Dr Uwins said until now, there have been no living
representatives for
the Martian nano-organisms or other fossil nanobacteria described
on
Earth in various rock types.
"Therefore it has been hard to convince the scientific
community that
the fossil Martian nanostructures could be remnant life
forms," she
said.
Dr Uwins said factors that had made a big difference to the
University
of Queensland investigations had been the multi-disciplinary
nature of
the Centre for Microscopy and Microanalysis, and access to the
$750,000
ultra high resolution Jeol 890 scanning electron microscope. The
instrument is capable of one million times resolution, and is one
of
only a handful of such microscopes in the world.
She said while the researchers did not yet have conclusive
evidence for
reproduction and metabolism in nanobes, and while they had not
determined their evolutionary development, their evidence
strongly
suggested the existence of nanobes as biological organisms.
Media:
For further information, contact Dr Uwins, telephone work 07 3365
4694
email: p.uwins@mailbox.uq.edu.au
[Image caption: http://www.uq.edu.au/uni-news-media/Uwins.jpg]
=================
(2) UPDATING IGNATIUS DONNELLY'S FANCIFUL CATASTROPHISM
From Richard Meehan <meehan@stanford.edu>
Hi Benny:
I've been working on a major rewrite of my "Ignatius
Donnelly" web
project which is meant to present the idea of mid-holocene
catastrophism in an entertaining but also scientifically
responsible
way. The site of the main table of contents is:
http://www.stanford.edu/~meehan/donnellyr/contents.html
In case this is a little too fanciful for some readers, a summary
of
the the appropriately referenced material is given on:
http://www.stanford.edu/~meehan/donnellyr/summary.html
Dick Meehan
============
(3) DYNAMICS OF EARTH-CROSSING ASTEROIDS: THE PROTECTED TORO
ORBITS
A. Milani*) & S. Baccili: Dynamics of earth-crossing
asteroids: The
protected Toro orbits. CELESTIAL MECHANICS & DYNAMICAL
ASTRONOMY,
1998, Vol.71, No.1, pp.35-53
*) UNIVERSITY OF PISA,DEPT MATH,VIA BUONARROTI 2,I-56127
PISA,ITALY
Some asteroids in Earth-crossing orbits avoid close approaches by
entering in a mean motion resonance whenever the distance between
the
two orbits is small. These orbits are 'Toro class' according to
the
classification of (Milani et al., 1989). This protection
mechanism
can be understood by a semi-averaged model, in which the fast
variables are removed and the dynamical variables are the
critical
argument and the semimajor axis, with dependence upon a slow
parameter. The adiabatic invariant theory can be applied to this
model and accounts for all the qualitative features of the orbits
in
this class, including the onset of the libration when the orbit
distance is small. Because of the neglected perturbations by the
other planets, this theory is approximate and the adiabatic
invariant
is conserved only with low accuracy; moreover, the Toro state can
be
terminated by a close approach to another planet (typically
Venus).
'Would you tell me, please, which way I ought to go from here?'
'That
depends a good deal on where you want to get to,' said the Cat.
(Alice in Wonderland, L. Carroll). Copyright 1999, Institute for
Scientific Information Inc.
=================
(4) ASTEROID MEAN ELEMENTS
A. Milani*) & Z. Knezevic: Asteroid mean elements: Higher
order and
iterative theories. CELESTIAL MECHANICS & DYNAMICAL
ASTRONOMY, 1998,
Vol.71, No.1, pp.55-78
*) UNIVERSITY OF PISA,DIPARTIMENTO MATEMAT,SPACE MECH GRP,VIA
BUONARROTI 2,I-56127 PISA,ITALY
Mean orbital elements are obtained from osculating ones by
removing
the short periodic perturbations. Large catalogues of asteroid
mean
elements need to be computed, as a first step in the computation
of
proper elements, used to study asteroid families. The algorithms
for
this purpose available so far are only accurate to first order in
the
masses of the perturbing planets; the mean elements have
satisfactory
accuracy for most of the asteroid belt, but degraded accuracy in
the
neighbourhoods of the main mean motion resonances, especially the
2:1. We investigate a number of algorithms capable of improving
this
approximation; they belong to the two classes of Breiter-type
methods
and iterative methods. The former are obtained by applying some
higher order numerical integration scheme, such as Runge-Kutta,
to
the differential equation whose solution is a transformation
removing
the fast angular variables from the equations; they can be used
to
compute a full second order theory, however, only if the full
second
order determining function is explicitly computed, and this is
computationally too cumbersome for a complicated problem such as
the
N-body. The latter are fixed point iterative schemes, with the
first
order theory as an iteration step, used to compute the inverse
map
from mean to osculating elements; formally the method is first
order,
but because they implement a fixed frequency perturbation theory,
they are more accurate than conventional single iteration
methods; a
similar method is already in use in our computation of proper
from
mean elements. Many of these methods are tested on a sample of
asteroid orbits taken from the Themis family, up to the edge of
the
2:1 resonance, and the dispersion of the values of the computed
mean
semimajor axis over 100 000 years is used as quality control. The
results of these tests indicate that the iterative methods are
superior, in this specific application, to the Breiter methods,
in
accuracy and reliability This is understood as the result of the
cancellations occurring between second order perturbation terms:
the
incomplete second order theory, resulting from the use of a
Breiter
method with the first order determining function only, can be
less
accurate than complete, fixed frequency theories of the first
order.
We have therefore computed new catalogues of asteroid mean and
proper
elements, incorporating an iterative algorithm in both steps
(osculating to mean and mean to proper elements). This new data
set,
significantly more reliable even in the previously degraded
regions
of Themis acid Cybele, is in the public domain. Copyright 1999,
Institute for Scientific Information Inc.
==================
(5) THE 1996 LEONID SHOWER AS STUDIED WITH A POTASSIUM LIDAR
J. Hoffner*), U. von Zahn, W.J. McNeil, E. Murad: The 1996 Leonid
shower as studied with a potassium lidar: Observations and
inferred
meteoroid sizes. JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS,
1999,
Vol.104, No.A2, pp.2633-2643
*) LEIBNIZ INSTITUTE FOR ATMOSPHERIC PHYSICS,D-18225
KUHLUNGSBORN, GERMANY
We report on the observation and analysis of meteor trails that
are
detected by ground-based lidar tuned to the D-1 fine structure
line of
K. The lidar is located at Kuhlungsborn, Germany. The echo
profiles are
analyzed with a temporal resolution of about 1 s and altitude
resolution of 200 m. Identification of meteor trails in the large
archive of raw data is performed with help of an automated
computer
search code. During the peak of the Leonid meteor shower on the
morning
of November 17, 1996, we observed seven meteor trails between
0245 and
0445 UT. Their mean altitude was 89.0 km. The duration of
observation
of individual trails ranges from 3 s to similar to 30 min. We
model the
probability of observing a meteor trail by ground-based lidar as
a
function of both altitude distribution and duration of the
trails.
These distributions depend on the mass distribution, entry
velocity,
and entry angle of the meteoroids, on the altitude-dependent
chemical
and dynamical lifetimes of the released K atom, and on the
absolute
detection sensitivity of our lidar experiment. From the modeling,
we
derive the statistical likelihood of detection of trails from
meteoroids of a particular size. These bracket quite well the
observed
trails. The model also gives estimates of the probable size of
the
meteoroids based on characteristics of individual trails.
Copyright
1999, Institute for Scientific Information Inc.
==================
(6) NEW RESEARCH ON THE PERMIAN-TRIASSIC BOUNDAY
S. Kershaw*), T.S. Zhang, G.Z. Lan: A microbialite carbonate
crust at
the Permian-Triassic boundary in South China, and its
palaeoenvironmental significance. PALAEOGEOGRAPHY
PALAEOCLIMATOLOGY
PALAEOECOLOGY, 1999, Vol.146, No.1-4, pp.1-18
*) BRUNEL UNIVERSITY,DEPT GEOG & EARTH SCI, UXBRIDGE
UB8 3PH,MIDDX,ENGLAND
A 1 m thick carbonate crust, layered and commonly domal, caps
crinoidal
limestones on reef complexes of the top Permian Changxing
Formation in
the Huaying Mountains, eastern Sichuan, China. The crust's
stratigraphic level lies at a sharp change in facies, and is
overlain
by poorly fossiliferous laminated micrites and shales of the
Lower
Triassic Feixianguan Formation. The crust therefore appears to
coincide
with the end-Permian extinction event, although the dating of the
strata is currently imprecise. The crust is composed mostly of
digitate
carbonate, locally thrombolitic, with remnant lobate fabric, and
resembles microbialites, but is mostly recrystallised and a
microbial
origin is unconfirmed. It is enclosed in micrite with pyrite
crystals,
ostracode and other shell debris. The crust is absent from
interreef
areas. Previous interpretations of karstification and calcrete
formation are not upheld, and the facies were deposited under
water.
Overlying sediments are low energy, with abundant ferroan calcite
and
pyrite, reflecting anoxia associated with rising sea level.
Various
interpretations of the crust are possible: (1) it was organic,
and
microbia grew preferentially on topographic highs of reef tops;
(2)
microbia were a disaster biota in the absence of grazers, (3)
microbia
took advantage of favourable conditions for calcification,
associated
with a rapidly rising environmental-CO2 content during the Late
Permian; (4) the crust was an inorganic precipitate associated
with
CO2-rich water. Microbial crusts are rare after the Cambrian, but
whether this crust is organic or not, its presence in these
strata
reinforces the view that oceanic-atmospheric conditions in the
Permian-Triassic boundary interval were unusual. (C) 1999
Elsevier
Science B.V. All rights reserved.
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