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(meteorobs) Excerpts from "CCNet 27/2001 - 16 February 2001"
Extensive set of meteor-related excerpts today! And one item selected
for what I admit are purely editorial reasons: I hope our readers will
forgive this isolated slip in my usual meteors-only policy.
Note also the excellent research result on the presence of larger icy
meteoroids (near and dear to fireball lovers) in common streams. This
comes from our own Digest reader, Martin Beech, and his colleague!
Clear skies,
Lew Gramer <owner-meteorobs@jovian.com>
------- Forwarded Message
From: Benny Peiser <B.J.Peiser@livjm.acdot uk>
To: cambridge-conference <cambridge-conference@livjm.acdot uk>
Subject: CCNet, 16 February 2001
Date: Fri, 16 Feb 2001 11:00:05 -0000
CCNet 27/2001 - 16 February 2001
--------------------------------
"The core system by which the scientific community allots prestige
(in terms of oral presentations at major meetings and publication in
major journals) and funding is a non-validated charade whose processes
generate results little better than does chance. Given the fact that most
reviewers are likely to be mainstream and broadly supportive of the
existing organization of the scientific enterprise, it would not be
surprising if the likelihood of support for truly innovative research
was considerably less than that provided by chance."
--David F. Horrobin, BioMedNet, 2 February 2001
(1) FLAMING METEOR OBSERVED OVER NORTHERN IRELAND
Ron Baalke <baalke@jpl.nasadot gov>
[...]
(3) ASTEROID MISSION EXTENDED
BBC, 15 February 2001
[...]
(5) SOMETHING ROTTEN AT THE CORE OF SCIENCE?
BioMedNet, 2 February 2001
[...]
(8) IRIDIUM IN COMETS
Jeremy Tatum <UNIVERSE@uvvm.UVicdot ca>
[...]
(11) HOW MANY RUBBLE PILES ARE IN THE ASTEROID BELT?
Bagatin AC, Petit JM, Farinella P
[...]
(13) BASIC TARGETING STATEGIES FOR RENDEZVOUS AND FLYBY MISSIONS
TO NEAR-EARTH ASTEROIDS
Perozzi E, Rossi A, Valsecchi GB
[...]
(15) ENDURANCE LIFETIME OF ICE FRAGMENTS IN COMETARY STREAMS
Beech M, Nikolova S
(16) NUMERICAL EVALUATION OF THE YARKOVSKY EFFECT
Spitale J, Greenberg R
[...]
==============
(1) FLAMING METEOR OBSERVED OVER NORTHERN IRELAND
>From Ron Baalke <baalke@jpl.nasadot gov>
http://www.ic24dot net/mgn/THE_MIRROR/NEWS/P11S6.html
Fireball Riddle
'Flaming meteor' sparked 2-day hunt for plane crash
The Mirror (United Kingddom)
February 15, 2001
THE fireball which sparked a major search operation for a crashed plane may
have been a meteor, it was learned yesterday.
Helicopters, troops, police and ambulance crews were mobilised after locals
saw the flames and smoke streaking across the sky near the border.
It was feared that a light aircraft had gone down. But a two-day search
operation was called off last night as speculation grew it was an
extra-terrestrial rock.
Full story here:
http://www.ic24dot net/mgn/THE_MIRROR/NEWS/P11S6.html
===========
(3) ASTEROID MISSION EXTENDED
>From the BBC, 15 February 2001
http://news.bbc.codot uk/hi/english/sci/tech/newsid_1170000/1170499.stm
Nasa is still receiving signals from the first spacecraft to land on an
asteroid and has extended the mission by 10 days to gather important
scientific information. Scientists hope the data from Near (Near Earth
Asteroid Rendezvous) Shoemaker, which landed on Eros on Monday, will help
them understand the relationship between space rocks like Eros and
meteorites that have fallen to Earth.
Dr Jay Bergstralh of the American Space Agency Nasa, said on Wednesday: "We
will extend the operation by 10 days to gather further data on the
abundances of elements on the asteroid."
At a post-landing press briefing at Nasa's headquarters in Washington DC,
the mission team revealed details of how they landed the craft.
'Success'
"The secret of success here is that we did our homework several times," said
Dr Bobby Williams of Nasa's Jet Propulsion Laboratory, Pasadena, California.
"For a spacecraft that is not built to land this came off extraordinarily
well."
More than 60 images were taken by Near Shoemaker craft on its descent.
The pictures show boulders strewn across the surface of Eros, some of them
twice the size of Near, others only the size of a golf ball.
While they give clues to the make-up of the asteroid, they also raise
further mysteries.
"Some of the big questions have been answered but fortunately many mysteries
remain," said Joseph Veverka, Imaging Team Leader, Cornell University,
Ithaca, New York.
"That is the whole point of exploration and discovery."
Faster, cheaper, better
The touchdown ended a five-year journey by the craft, one of the first of
Nasa's "faster, better, cheaper" missions.
It was a remarkable feat for a probe that was only designed to orbit, rather
than land. And, against all odds, Near is still transmitting signals to
mission control.
Scientists believe that the signals could continue for the next few weeks
until the Sun, which powers the craft's solar panels, moves out of range.
Before the touchdown, Near had already orbited Eros for a year, sending back
some 160,000 images of the rocky surface.
Asteroids, material left over from the formation of the Solar System, are
rocky and metallic objects that orbit the Sun but are too small to be
considered planets.
Because asteroids are material from the very early Solar System, scientists
are interested in their composition.
Data on the object could also be useful well into the future, as there is a
chance that Eros could collide with the earth in roughly 1.5m years.
Copyright 2001, BBC
===============
(5) SOMETHING ROTTEN AT THE CORE OF SCIENCE?
>From BioMedNet, 2 February 2001
http://news.bmn.com/hmsbeagle/95/viewpts/op_ed
By David F. Horrobin
Reprinted with permission from Trends in Pharmacological Sciences, Vol. 22,
No. 2, February 2001
Posted February 2, 2001 7 Issue 95
Abstract
A recent U.S. Supreme Court decision and an analysis of the peer review
system substantiate complaints about this fundamental aspect of scientific
research. Far from filtering out junk science, peer review may be blocking
the flow of innovation and corrupting public support of science.
The U.S. Supreme Court has recently been wrestling with the issues of the
acceptability and reliability of scientific evidence. In its judgement in
the case of Daubert v. Merrell Dow, the court attempted to set guidelines
for U.S. judges to follow when listening to scientific experts. Whether or
not findings had been published in a peer-reviewed journal provided one
important criterion. But in a key caveat, the court emphasized that peer
review might sometimes be flawed, and that therefore this criterion was not
unequivocal evidence of validity or otherwise. A recent analysis of peer
review adds to this controversy by identifying an alarming lack of
correlation between reviewers' recommendations.
The Supreme Court questioned the authority of peer review.
Many scientists and lawyers are unhappy about the admission by the top legal
authority in the United States that peer review might in some circumstances
be flawed [1]. David Goodstein, writing in the Guide to the Federal Rules of
Evidence - one of whose functions is to interpret the judgement in the case
of Daubert - states that "Peer review is one of the sacred pillars of the
scientific edifice" [2]. In public, at least, almost all scientists would
agree. Those who disagree are almost always dismissed in pejorative terms
such as "maverick," "failure," and "driven by bitterness."
Peer review is central to the organization of modern science. The
peer-review process for submitted manuscripts is a crucial determinant of
what sees the light of day in a particular journal. Fortunately, it is less
effective in blocking publication completely; there are so many journals
that most even modestly competent studies will be published provided that
the authors are determined enough. The publication might not be in a
prestigious journal, but at least it will get into print. However, peer
review is also the process that controls access to funding, and here the
situation becomes much more serious. There might often be only two or three
realistic sources of funding for a project, and the networks of reviewers
for these sources are often interacting and interlocking. Failure to pass
the peer-review process might well mean that a project is never funded.
Science bases its presumed authority in the world on the reliability and
objectivity of the evidence that is produced. If the pronouncements of
science are to be greeted with public confidence - and there is plenty of
evidence to suggest that such confidence is low and eroding - it should be
able to demonstrate that peer review, "one of the sacred pillars of the
scientific edifice," is a process that has been validated objectively as a
reliable process for putting a stamp of approval on work that has been done.
Peer review should also have been validated as a reliable method for making
appropriate choices as to what work should be done. Yet when one looks for
that evidence it is simply not there.
Why not apply scientific methods to the peer review process?
For 30 years or so, I and others have been pointing out the fallibility of
peer review and have been calling for much more openness and objective
evaluation of its procedures [3-5]. For the most part, the scientific
establishment, its journals, and its grant-giving bodies have resisted such
open evaluation. They fail to understand that if a process that is as
central to the scientific endeavor as peer review has no validated
experimental base, and if it consistently refuses open scrutiny, it is not
surprising that the public is increasingly skeptical about the agenda and
the conclusions of science.
Largely because of this antagonism to openness and evaluation, there is a
great lack of good evidence either way concerning the objectivity and
validity of peer review. What evidence there is does not give confidence but
is open to many criticisms. Now, Peter Rothwell and Christopher Martyn have
thrown a bombshell [6]. Their conclusions are measured and cautious, but
there is little doubt that they have provided solid evidence of something
truly rotten at the core of science.
Forget the reviewers. Just flip a coin.
Rothwell and Martyn performed a detailed evaluation of the reviews of papers
submitted to two neuroscience journals. Each journal normally sent papers
out to two reviewers. Reviews of abstracts and oral presentations sent to
two neuroscience meetings were also evaluated. One meeting sent its
abstracts to 16 reviewers and the other to 14 reviewers, which provides a
good opportunity for statistical evaluation. Rothwell and Martyn analyzed
the correlations among reviewers' recommendations by analysis of variance.
Their report should be read in full; however, the conclusions are alarmingly
clear. For one journal, the relationships among the reviewers' opinions were
no better than that obtained by chance. For the other journal, the
relationship was only fractionally better. For the meeting abstracts, the
content of the abstract accounted for only about 10 to 20 percent of the
variance in opinion of referees, and other factors accounted for 80 to 90
percent of the variance.
These appalling figures will not be surprising to critics of peer review,
but they give solid substance to what these critics have been saying. The
core system by which the scientific community allots prestige (in terms of
oral presentations at major meetings and publication in major journals) and
funding is a non-validated charade whose processes generate results little
better than does chance. Given the fact that most reviewers are likely to be
mainstream and broadly supportive of the existing organization of the
scientific enterprise, it would not be surprising if the likelihood of
support for truly innovative research was considerably less than that
provided by chance.
Objective evaluation of grant proposals is a high priority.
Scientists frequently become very angry about the public's rejection of the
conclusions of the scientific process. However, the Rothwell and Martyn
findings, coming on top of so much other evidence, suggest that the public
might be right in groping its way to a conclusion that there is something
rotten in the state of science. Public support can only erode further if
science does not put its house in order and begin a real attempt to develop
validated processes for the distribution of publication rights, credit for
completed work, and funds for new work. Funding is the most important issue
that most urgently requires opening up to rigorous research and objective
evaluation.
What relevance does this have for pharmacology and pharmaceuticals? Despite
enormous amounts of hype and optimistic puffery, pharmaceutical research is
actually failing [7]. The annual number of new chemical entities submitted
for approval is steadily falling in spite of the enthusiasm for techniques
such as combinatorial chemistry, high-throughput screening, and
pharmacogenomics. The drive to merge pharmaceutical companies is driven by
failure, and not by success.
The peer review process may be stifling innovation.
Could the peer-review processes in both academia and industry have destroyed
rather than promoted innovation? In my own field of psychopharmacology,
could it be that peer review has ensured that in depression and
schizophrenia, we are still largely pursuing themes that were initiated in
the 1950s? Could peer review explain the fact that in both diseases the
efficacy of modern drugs is no better than those compounds developed in
1950? Even in terms of side-effects, where the differences between old and
new drugs are much hyped, modern research has failed substantially. Is it
really a success that 27 of every 100 patients taking the selective 5-HT
reuptake inhibitors stop treatment within six weeks compared with the 30 of
every 100 who take a 1950s tricyclic antidepressant compound? The
Rothwell-Martyn bombshell is a wake-up call to the cozy establishments who
run science. If science is to have any credibility - and also if it is to be
successful - the peer-review process must be put on a much sounder and
properly validated basis or scrapped altogether.
David F. Horrobin, a longtime critic of anonymous peer review, heads Laxdale
Ltd., which develops novel treatments for psychiatric disorders. In 1972 he
founded Medical Hypotheses, the only journal fully devoted to discussion of
ideas in medicine.
References
1. Daubert v. Merrel Dow Pharmaceuticals 509 U.S. 579 (1993), 509, 579.
http://caselaw.lp.findlaw.com/scripts/getcase.pl?navby=search&court=US&case=
/us/509/579.html)
2. Goodstein, D. 2000. How Science Works. In U.S. Federal Judiciary
Reference Manual on Evidence, pp. 66-72.
3. Horrobin, D.F. 1990. The philosophical basis of peer review and the
suppression of innovation. J. Am. Med. Assoc. 263:1438-1441.
4. Horrobin, D.F. 1996. Peer review of grant applications: A harbinger for
mediocrity in clinical research? Lancet 348:1293-1295.
5. Horrobin, D.F. 1981-1982. Peer review: Is the good the enemy of the best?
J. Res. Commun. Stud. 3:327-334.
6. Rothwell, P.M. and Martyn, C.N. 2000. Reproducibility of peer review in
clinical neuroscience: Is agreement between reviewers any greater than would
be expected by chance alone? Brain 123:1964-1969.
7. Horrobin, D.F. 2000. Innovation in the pharmaceutical industry. J. R.
Soc. Med. 93:341-345.
Copyright 2001, ) Elsevier Science Limited 2000
============================
* LETTERS TO THE MODERATOR *
============================
(8) IRIDIUM IN COMETS
>From Jeremy Tatum <UNIVERSE@uvvm.UVicdot ca>
It is argued by some that the presence of iridium in the K/T boundary layer
is evidence of a cometary collision; it is argued by others that the
presence of iridium in volcanic magmas militates against the cometary
hypothesis.
The presence or absence of iridium in the K/T boundary layer or in volcanic
magmas tells us nothing whatever about whether or not a comet may at some
time have collided with Earth, for the following reasons.
1. Iridium has never been detected in the spectrum of any comet.
2. You would not expect to detect iridium in the spectrum of a comet
since iridium is a highly refractory element which could be vaporized
and its emission spectrum excited when the comet is so close to the Sun
(i.e. in the daytime sky) so that a spectrum cannot be obtained.
3. Even if iridium were detected in a cometary spectrum, this would not
enable us to determine how much iridium was in the comet because the
necessary oscillator strengths of the relevant lines have not been
determined in the laboratory.
As a consequence of this, it is not known by cometary scientists whether
iridium does or does not occur in comets, or, if it does, how much.
Iridium may be present in meteorites, but, as far as I know, it has never
been detected or identified in an asteroid, although presumably the
gamma-ray spectrometer aboard NEAR-Shoemaker has the capability of doing so
now.
It is high time that a brake was put on the highly speculative scenari about
the early history of the solar system that are being published on an almost
daily basis with little or no foundation of scientific fact or
understanding.
Jeremy B. Tatum
=============
* ABSTRACTS *
=============
(11) HOW MANY RUBBLE PILES ARE IN THE ASTEROID BELT?
Bagatin AC, Petit JM, Farinella P: How many rubble piles are in the asteroid
belt?
ICARUS 149: (1) 198-209 JAN 2001
We have developed a new Version of the code built by Campo Bagatin et al.
(1994a, Planet. Space Sci. 42, 1079- 1092; 1994b, ibid., 42, 1099-1107) and
Campo Bagatin (1998, Ph.D. thesis, University of Valencia) to model the
collisional evolution of the asteroid size distribution. The new code
distinguishes between "intact," unfractured asteroids that did not undergo
catastrophic collisions and asteroids converted by energetic collisions into
reaccumulated bodies, or "rubble piles." The distinction can also be made on
a physical ground by assigning different collisional parameters to the two
kinds of objects, with the objective of simulating the different responses
to energetic impacts that rubble piles may have-due to their different
structure-in comparison to unshattered bodies. Rubble-piles abundance when
such targets are supposed to transfer less kinetic energy to the fragments
turns out to be generally higher than monolithic asteroids.
We have run a number of simulations of the collisional evolution process to
assess the size range where reaccumulated bodies should be expected to be
abundant in the main asteroid belt. We find that this diameter range goes
from about 10 to 100 km, but may extend to smaller or larger bodies,
depending on the prevailing collisional response parameters, such as the
strength of the material the strength scaling law, the fraction of kinetic
energy of the impact transferred to the fragments, and the reaccumulation
model. Both the size range and the resulting fraction of rubble piles vary
widely depending on the input parameters, which reflects the large
uncertainties still present in the modelization of high-velocity impact
outcomes. In particular, the simulations that take into account the derived
"hydrocode" scaling laws (Davis et at. 1994, Planet. Space Sci. 42, 599-610)
show that nearly 100% of the main belt asteroids larger than a few
kilometers should be reaccumulated objects, On the other hand, the present
code shows that the scaling law recently proposed by Durda et al. (1998,
Icarus 135, 431-440) produces almost no rubble pile. This scaling law was
pro-posed to match the actual population of asteroids, which it fails to do
if collisional processes are accounted for in a self-consistent way. (C)
2000 Academic Press.
Addresses:
Bagatin AC, Observ Cote Azur, F-06003 Nice, France.
Observ Cote Azur, F-06003 Nice, France.
==========
(13) BASIC TARGETING STATEGIES FOR RENDEZVOUS AND FLYBY MISSIONS TO
NEAR-EARTH ASTEROIDS
Perozzi E, Rossi A, Valsecchi GB: Basic targeting strategies for rendezvous
and flyby missions to the near-Earth asteroids
PLANETARY AND SPACE SCIENCE 49: (1) 3-22 JAN 2001
Missions to asteroids and comets are becoming increasingly feasible both
from a technical and a financial point of view. in particular, those
directed towards the Near-Earth Asteroids have proven suitable for a
low-cost approach, thus attracting the major space agencies as well as
private companies. The choice of a suitable target involves both scientific
relevance and mission design considerations, being often a difficult task to
accomplish due to the limited energy budget at disposal. The aim of this
paper is to provide an approach to basic trajectory design which allows to
account for both aspects of the problem, taking into account scientific and
technical information. A global characterization of the Near-Earth Asteroids
population carried out on the basis of their dynamics, physical properties
and flight dynamics considerations, allows to identify a group of candidates
which satisfy both, the scientific and engineering requirements. The
feasibility of rendezvous and flyby missions towards them is then discussed
and the possibility of repeated encounters with the same object is
investigated, as an intermediate scenario. Within this framework, the
capability of present and near future launch and propulsion systems for
interplanetary missions is also addressed. (C) 2001 Elsevier Science Ltd.
All rights reserved.
Addresses:
Perozzi E, Observ Paris Meudon, DESPA, 5 Pl Jules Janssen, F-92195 Meudon,
France.
Observ Paris Meudon, DESPA, F-92195 Meudon, France.
Telespazio, I-00156 Rome, Italy.
CNR, Ist CNUCE, I-56126 Pisa, Italy.
CNR, Area Ric, Reparto Planetol, IAS, I-00133 Rome, Italy.
===========
(15) ENDURANCE LIFETIME OF ICE FRAGMENTS IN COMETARY STREAMS
Beech M, Nikolova S: The endurance lifetime of ice fragments in
cometary streams
PLANETARY AND SPACE SCIENCE 49: (1) 23-29 JAN 2001
The endurance lifetime against sublimation of meter- to decameter-sized ice
fragments are calculated for typical cometary orbits. It is found that such
bodies can survive for multiple perihelion passages. For fragments traveling
along orbits similar to those of typical meteor shower producing comets, the
sublimation mass loss rate drives radial variations equivalent to 1-0.5 m
per orbit. We review the available data with respect to the possible
presence of large objects within the Perseid, Lyrid, Leonid and alpha
Capricornid streams. Invoking cometary aging and surface fragmentation
events as the mechanism for placing large meteoroids within cometary
streams, we find no compelling reasons to doubt that large meteoroids are
intermittently present in most, if not all cometary-derived meteoroid
assemblages. (C) 2001 Elsevier Science Ltd. All rights reserved.
Addresses:
Beech M, Univ Regina, Camp Coll, 3737 Wascana Pkwy, Regina, SK S4S 0A2,
Canada.
Univ Regina, Camp Coll, Regina, SK S4S 0A2, Canada.
Univ Regina, Dept Phys, Regina, SK S4S 0A2, Canada.
Univ Western Ontario, Dept Phys & Astron, London, ON N6A 3K7, Canada.
===========
(16) NUMERICAL EVALUATION OF THE YARKOVSKY EFFECT
Spitale J, Greenberg R: Numerical evaluation of the general Yarkovsky
effect: Effects on semimajor axis
ICARUS 149: (1) 222-234 JAN 2001
The Yarkovsky effect may play a key role in the orbital evolution of
asteroids and near-Earth objects. To evaluate the acceleration under a wide
range of conditions, a three-dimensional finite-difference solution to the
heat equation is applied to homogeneous, spherical stony bodies with 1-,
10-, and 100-m diameters. This approach employs neither the linearized
boundary conditions, the plane-parallel heat flow approximation, nor the
assumption of fast rotation used in earlier work. Thus we can explore a wide
range of orbital elements and physical properties. Our work agrees well with
earlier results in the regimes where their approximations are valid. We
investigate a wide range of spin states, including both the "seasonal" (very
fast rotation) and "diurnal" (zero obliquity) extremes of the Yarkovsky
effect. We find that, for orbits with high eccentricity, the semimajor axis
can change much faster than for circular orbits, For such orbits, the
orientation of the rotation axis with respect to the direction of pericenter
is critical in determining the evolution. A stony main-belt asteroid of
diameter 1 m on a high-eccentricity orbit could change its semimajor axis by
more than 1AU in 1.5 Myr. (C) 2001 Academic Press.
Addresses:
Spitale J, Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA.
Univ Arizona, Lunar & Planetary Lab, Tucson, AZ 85721 USA.
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