PLEASE NOTE:


*

CCNet, 38/2000 - 23 March 2000
------------------------------


     "We'll have to be patient and await more observations [of Eros],
     especially from the lower orbits where the x-ray and gamma ray
     spectrometers were designed to operate. Gene [Shoemaker] would
     have had difficulty with the notion of being patient at Eros - he
     wanted to go there and bang on it with a hammer - but he would
     have understood."
         -- Andrew Cheng, NEAR-SHOEMAKER Project Scientist,
                          in his tribute to Gene Shoemaker


(1) NEAR-SHOEMAKER SCIENCE UPDATE
    Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>

(2) WAS MARS SHAPED BY GLACIERS?
    Andrew Yee <ayee@nova.astro.utoronto.ca>

(3) NASA REJECTS JAMES OBERG’S INVESTIGATIVE MPL FAILURE STORY
    NASANews@hq.nasa.gov

(4) NASA CHIEF ADMITS MANAGEMENT ERRORS
    MSNBC Space News, 22 March 2000

(5) ASTRONOMERS DISCOVER FREE-FLOATING PLANETS IN THE ORION   
    NEBULA
    Jacqueline Mitton <jmitton@dial.pipex.com>

(6) FOSSILIZED BACTERIA FOUND IN ANCIENT METEORITE
    Michael Paine <mpaine@tpgi.com.au>

(7) DEGRADATION SIGNATURES AROUND IMPACT CRATERS
    J.A. Grant, SUNY COLL BUFFALO

(8) IMPACT CRATERS IN 3D
    D. Wallis et al., UNIVERSITY OF KENT

(9) JAPANESE CONTRIBUTION TO METEOROID & SPACE DEBRIS   
    MEASUREMENT
    H. Yano, INST SPACE & ASTRONAUT SCI

(10) POSSIBLE CAUSES OF CYCLICAL IMPACT EVENTS
     Michael Rampino <mrr1@is3.nyu.edu>

(11) RUMOURS AND ALLEGATIONS
     Jeremy Tatum <UNIVERSE@uvvm.UVic.CA>


============
(1) NEAR-SHOEMAKER SCIENCE UPDATE

From Ron Baalke <BAALKE@kelvin.jpl.nasa.gov>

NEAR-Shoemaker Science Update
March 22, 2000
http://near.jhuapl.edu/news/sci_updates/00mar22.html

Last week the NEAR spacecraft was renamed "NEAR Shoemaker," in honor of
the late Eugene M. Shoemaker, a pioneer in the study of asteroid and
comet impacts on Earth and other planets. It is largely because of
Gene's work that we know that the famous Meteor Crater in Arizona (also
called Barringer Crater) was indeed created by the impact of a 15-meter
iron-rich meteoroid and not by a volcano. While many scientists
suspected an impact origin, including Barringer himself, it was
Shoemaker and his colleague Chao's discovery of the high pressure
silicate mineral coesite that finally convinced skeptics.

Gene was also heavily involved in the Apollo missions that resolved one
of the leading scientific controversies of our time, whether the
craters on the Moon were formed by volcanoes or by impacts. We now know
that the surface of the Moon is actually saturated with impact craters
and that even the largest features we see, those that make up the "man
in the moon", lie within the scars of giant impacts. These features are
dark because, later in the moon's history, the giant impact scars were
filled with volcanic lavas. The Moon's surface records a period of
violent bombardment in the early history of the solar system, a
bombardment which the Earth itself did not escape. Of course, on Earth
the record of ancient giant impacts has been mostly erased by the
actions of weather and plate tectonics. Gene was among the first to
recognize the importance of large impacts for the geologic history of
the Earth and for the evolution of life on Earth.

Since the projectiles that bombarded the Moon, the Earth, and other
terrestrial planets were asteroids and comets, Gene initiated
telescopic observing programs to search for such objects in orbits
close to Earth's orbit (that is, near-Earth asteroids and comets) as
well as in more distant orbits. He and David Levy discovered the comet
Shoemaker-Levy 9 that plunged into Jupiter in 1994, after splitting
into more than 20 fragments, temporarily creating dark spots in
Jupiter's clouds larger than the Earth.

NEAR Shoemaker is now orbiting one of the largest of the near-Earth
asteroids, 433 Eros. Gene always thought of the near-Earth asteroids as
"roadcuts in the heavens", which would have fascinating and important
stories to tell about the formation of the planets. We all have the
experience of driving through a roadcut on the highway and looking at
exposed layers of sediment or rock on either side, which would reveal
something of the geologic history of that particular site. How
appropriate it is that we now see fantastic systems of linear features
- ridges, grooves, and chains of craters or pits - all around the
surface of Eros. Were the linear features formed by ancient geologic
activity on the parent body of Eros, making Eros possibly a 'roadcut'
through the parent body from which it was derived? Or were the linear
features formed by later processes? Our task is now to find the
evidence that would indicate which of these possibilities may be
correct.

One important line of evidence will come from NEAR's x-ray and
gamma-ray spectrometers, which will measure the elemental compositions
of surface materials. Last week, NEAR recorded the first detections of
x-ray emissions from an asteroid. NEAR's x-ray spectrometer was able to
identify emission from the elements silicon, aluminum, magnesium,
calcium and iron during a large solar flare on March 2, 2000. The flare
bombarded the asteroid's surface with an unusually high intensity of
x-rays, enabling NEAR's x-ray spectrometer to detect the asteroid
emissions at a range of more than 200 kilometers from the surface. From
that one observation, we were not able to determine quantitative
abundances of these elements, which is the information that might tell
us whether Eros is from a differentiated parent body (one large enough
to have melted in the interior and separated into heavier and lighter
constituents) or from a more primitive parent body. We'll have to be
patient and await more observations, especially from the lower
orbits where the x-ray and gamma ray spectrometers were designed to
operate. Gene would have had difficulty with the notion of being
patient at Eros - he wanted to go there and bang on it with a hammer -
but he would have understood.

Andrew Cheng
NEAR Project Scientist

==================
(2) WAS MARS SHAPED BY GLACIERS?

From Andrew Yee <ayee@nova.astro.utoronto.ca>

New Scientist
http://www.newscientist.com

UK Contact:
Claire Bowles, claire.bowles@rbi.co.uk, 44-207-331-2751
US Contact:
New Scientist Washington Office, newscidc@idt.net, 202-452-1178

EMBARGOED FOR RELEASE: March 22, 2000, 2 p.m. EST

Was Mars shaped by glaciers?

Melting glaciers rather than flowing surface water could have carved
out the Red Planet's distinctive valleys.

Branching networks of small valleys have led many scientists to
conclude that rivers of running water once flowed freely across the
surface of Mars. But this would mean that the Red Planet once had a
much warmer climate than it does today and, apart from its valleys,
there is no evidence to suggest that Mars was ever warm (New Scientist,
17 April 1999, p 48).

But Pascal Lee, a planetary scientist at NASA's Ames Research Center in
Mountain View, California, says the answer may be found on Devon Island
in the Canadian Arctic, where he is studying valleys carved by glacial
meltwater. "What we've been finding on Devon Island," says Lee, "is a wide
variety of valley types, from canyons to little networks of small
valleys, that bear an uncanny resemblance to specific counterparts on
Mars."

In particular, he says, the Martian valleys "cut through a desert that
otherwise has very little sign of water flowing nearby". The constant
width and depth of Martian valleys over long distances, their flat
floors and steep walls are all distinctive features also found on Devon
Island, but uncommon on river networks.

Lee believes that other Martian landforms, notably some large canyons
on the west end of Vallis Marineris, could actually have been carved by
flowing glacial ice. Devon Island also has canyons like these, he told
the 31st Lunar and Planetary Institute Science Conference in Houston,
Texas, last week.

If Lee is correct, Mars may have had a cold climate, in which snowfall
piled up to form glaciers that later melted in the heat generated
inside the planet. Mars expert Jim Head of Brown University, Rhode
Island, welcomes Lee's work, saying the analogy to Devon Island is
helping him visualise how melting snow might have produced valleys on
Mars.

Reporter: Henry Bortman

New Scientist issue: 25th March 2000

PLEASE MENTION NEW SCIENTIST AS THE SOURCE OF THIS STORY AND, IF
PUBLISHING ONLINE, PLEASE CARRY A HYPERLINK TO:
   http://www.newscientist.com

==============
(3) NASA REJECTS JAMES OBERG’S INVESTIGATIVE MPL FAILURE STORY

From NASANews@hq.nasa.gov

Peggy Wilhide
Headquarters, Washington, DC             March 22, 2000
(Phone: 202/ 358-1898)

Brian Welch
Headquarters, Washington, DC
(Phone: 202/ 358-1600)

Don Savage
Headquarters, Washington, DC
(Phone: 202/ 358-1547)

RELEASE: 00-43

NASA'S RESPONSE TO UPI'S MARCH 21 MARS POLAR LANDER STORY

James Oberg of UPI claims that NASA knew there was a problem with the
Mars Polar Lander propulsion system prior to the Dec. 3 landing attempt
and "withheld this conclusion from the public."  NASA categorically
denies this charge.  Here's what NASA did and what NASA said:

*   The Stephenson report, phase 1, was released to the public on
November 10, 1999 during a press conference at NASA Headquarters. 

*   The report made 11 different references to technical issues or
concerns involving the propulsion system and the Entry, Descent
and Landing (EDL) sequence.

*   This issue was specifically addressed in the press conference
and in "MPL Observation No. 5" and other public recommendations of
the Stephenson Phase 1 report.  It was entitled, "Cold Firing of
Thrusters," and dealt in detail with the catalyst bed issue cited
by Mr. Oberg of UPI in his March 21 story, "NASA Knew Mars Polar
Lander Doomed."

*   Had UPI researched the public documents released on Nov. 10,
which have been available online at the NASA Home Page, the
reporter would have been able to conclude that NASA did indeed
publicly address propulsion issues, and specifically, the
propulsion system's "catalyst bed" temperature concern.

*   Based on this review, NASA knew about the concerns with the
propulsion system, NASA took corrective action, and NASA hid
nothing from the public.  We made our concerns known in early
November.

*   Several failure scenarios have been reported in the press over
the last few weeks, including the lander legs microswitch issue. 
Outlets such as the Denver Post, Space Daily, and National Public
Radio's "All Things Considered" have covered this angle.  There is
nothing new in the UPI report relating to this specific issue. 
The lander legs issue is among the failure modes we are studying.

*   Both the Stephenson and Casani (John Casani, retired JPL
flight programs head and also director of mission assurance) teams
have conducted intensive reviews relating to Mars Polar Lander,
and their teams have surfaced no evidence relating to thruster
acceptance testing irregularities as alleged by UPI.  In fact,
members of the review teams are using words like "bunk," "complete
nonsense," and "wacko," to describe their reactions to UPI's
charge. 

=================
(4) NASA CHIEF ADMITS MANAGEMENT ERRORS

From MSNBC Space News, 22 March 2000
http://msnbc.com/news/385617.asp?cp1=1                                              

ASSOCIATED PRESS

Goldin absorbs criticism from senators, agrees that work force was
‘too thin’

WASHINGTON, March 22 —  NASA, trying to do more missions with less
money and fewer people, made management mistakes that contributed to a
string of recent failures in space, the chief of the agency said
Wednesday.

“WE PROBABLY cut too tight” in reducing the NASA work force from 25,000
to 18,500 over the last seven years, Daniel Goldin, NASA’s
administrator, told the Senate Commerce subcommittee on space. “We
found we were really too thin.”

Goldin said the agency lost many veteran engineers over those years,
and there was inadequate training and mentoring for young,
inexperienced workers who were hired.

Additionally, he said, there was a failure in communication between
engineers and technicians doing the work and the management personnel
overseeing it. “There was no good communication feedback,” Goldin
said. “People were talking and we weren’t hearing them.”

FULL STORY at:
http://msnbc.com/news/385617.asp?cp1=1                                              

============
(5) ASTRONOMERS DISCOVER FREE-FLOATING PLANETS IN THE ORION   
    NEBULA

From Jacqueline Mitton <jmitton@dial.pipex.com>

Royal Astronomical Society Press Notice

Date: 22 March 2000
For immediate release

Ref. PN 00/04

ISSUED BY:

Dr Jacqueline Mitton
RAS Press Officer
Office & home phone: Cambridge ((0)1223) 564914
FAX: Cambridge ((0)1223) 572892
E-mail: jmitton@dial.pipex.com
RAS web: www.ras.org.uk/press/press.htm

----------------------------------------------------------------------------
Contacts for this release:

Dr Philip Lucas, University of Hertfordshire
Phone: 01707 286070
pwl@star.herts.ac.uk

Dr Patrick Roche, University of Oxford
Phone: 01865 273338
pfr@astro.ox.ac.uk
----------------------------------------------------------------------------

ASTRONOMERS DISCOVER FREE-FLOATING PLANETS IN
THE ORION NEBULA

The most sensitive survey ever undertaken of the region in the Orion
Nebula where new stars are forming has revealed 13 "free-floating
planets" as well as more than one hundred very young brown dwarfs.
The discovery was made by Dr Philip Lucas of the University of
Hertfordshire and Dr Patrick Roche of the University of Oxford using
a new camera on the United Kingdom Infrared Telescope (UKIRT) in
Hawaii. Their results will be published in the Monthly Notices of the
Royal Astronomical Society.

Brown dwarfs are objects that might have become stars, but never
accumulated sufficient material. With less than 8% of the Sun's mass,
they did not heat up enough inside to trigger the nuclear reactions
involving hydrogen that keep stars shining over long periods.
Nevertheless, they do produce some nuclear energy for a short time
(from deuterium, a rare isotope of hydrogen) if their mass exceeds
1.3% the Sun's mass -- about 13 times the mass of Jupiter.
Astronomers regard this as the minimum mass for a brown dwarf.

The new infrared survey of the Trapezium Cluster in the Orion Nebula,
turned up 13 objects below the 13 Jupiter-mass threshold. The mass of
the smallest is equivalent to no more than about 8 Jupiters. These objects
have been dubbed "free-floating planets". They give off only residual
heat left over from when they were born. By nature they are more like
the giant planets of our solar system than stars. However, they do
not orbit any star and drift through space by themselves. Only two
similar objects have previously been discovered. (Japanese
astronomers found them in the southern Chamaeleon Nebula.) The
discovery of thirteen more in one cluster suggests that they might be
very common.

Astronomers believe that most stars are born in giant molecular
clouds -- vast clumps of cold gas and dust. The nearest such cloud
lurks just behind the glowing gas of the Orion Nebula. The Trapezium
cluster at the heart of the Orion Nebula has recently broken out of
the dark molecular cloud. It is therefore the best place to look in
order to find out about the creation of stars, brown dwarfs and
free-floating planets in the rest of the Galaxy. The backdrop of the
Orion Molecular Cloud obscures everything that lies behind it, which
is very useful because it means that all the objects seen in this
part of the sky are members of the cluster, except for perhaps a
handful which lie in the foreground.

Because brown dwarfs and free floating planets quickly cool down,
they are easiest to find when they are young and still retain some
heat from the formation process. The objects in the Trapezium cluster
are mostly about one million years old -- very young compared to the
five-billion-year age of the Sun.

An interesting feature of this study is that no planets have been
found under 8 Jupiter masses. It may indicate that there is a limit
to how small these free-floating planets can be but even more
sensitive surveys will be needed to confirm this. In the meantime
UKIRT has been used to obtain spectra of about twenty of the brown
dwarfs and planets. The results are still being analysed but they
show the signature of water vapour that is expected in relatively
cool stars and brown dwarfs, at a temperature of a mere 2700 degrees
Centigrade. The planets will eventually cool down to earthly
temperatures but it is unlikely that they could ever sustain life.
Although the total number of brown dwarfs and planets in the
Trapezium may be similar to the number of stars, individually they
have less mass. If this a typical cluster, brown dwarfs and planets
do not contribute significantly to the dark matter that many
astronomers believe pervades the universe.

This survey is one of the first projects undertaken with the new
infrared camera UFTI, the UKIRT Fast Track Imager. It is the most
sensitive search yet conducted for low mass stellar and sub-stellar
objects. For all the objects they detected, Lucas and Roche measured
the strength of radiation given off at three standard wavelengths in
the near infrared (known as I, J and H). They used this data to
deduce the mass, luminosity and temperature of the objects. UFTI was
built by a team headed by Roche and Lucas at Oxford University in
1998, with the help of several British universities.

ILLUSTRATION

A low-resolution JPEG version is attached. This, and higher
resolution versions may be downloaded from the following web pages:

http://www-astro.physics.ox.ac.uk/~pwl/trapl.jpg
http://www-astro.physics.ox.ac.uk/~pwl/trapl.gif
http://www-astro.physics.ox.ac.uk/~pwl/trapl.tif

Caption: An infrared picture of the central part of the Orion Nebula
constructed from the three separate images taken with UFTI (the UKIRT
Fast Track Imager) on the United Kingdom Infrared Telescope. The
three colours used in this false colour image (blue, orange and red)
correspond to infrared radiation with wavelengths twice as long.
Hence, this picture shows Orion as we would see it if our eyes were
sensitive to light of twice the wavelength they are actually capable
of detecting. The picture shows stars, brown dwarfs and planets
together with diffuse starlight, which is scattered by tiny particles
of cosmic dust, and light emitted by energised gas. Infrared images
are vital for this work, as they penetrate the dusty clouds and are
able to pick up faint objects which cannot be seen in visible light
images.

NOTES
1. Both UFTI and UKIRT are funded by the Particle Physics and Astronomy
   Research Council.

2. The paper describing this work has been accepted for publication in the
   Monthly Notices of the Royal Astronomical Society, but the date of
   publication and is not yet available.

============
(6) FOSSILIZED BACTERIA FOUND IN ANCIENT METEORITE

From Michael Paine <mpaine@tpgi.com.au>

Dear Benny,

Re: The developmemts with the Martian meteorite ALH84001 reported by
Bill Wheaton (CCNet 21 Mar 2000). 

I hope the Yukon meteorite has been sufficiently protected from
contamination so that it can be examined for signs of ET. It now seems
that even those that fall on Antarctica can become contaminated with
local bugs after a few (thousand?) years.

regards
Michael Paine

(Claims of) Fossilized Bacteria Found in Ancient Meteorite
By Michael Paine,
Special to SPACE.com, posted: 07:51 am EST 21 February 2000
http://www.space.com/science/murchison_metor_000221.html

Russian scientists claim to have discovered fossils of primitive
extraterrestrial organisms in a meteorite thought to be a leftover from
the formation of the solar system.

Similar theories have met with skepticism in the past and there are
doubts about the latest claims. It seems that garden-variety microbes
love to feast on these carbon-rich meteorites.

Last year, at a conference on Astrobiology held in Denver, Dr Stanislav
Zhmur and colleagues from the Russian Academy of Sciences revealed that
they had found what looked like fossilized microorganisms in fragments
of several meteorites that fell on the rural town of Murchison in
South-East Australia in 1969.

Their electron microscope pictures and comments were recently posted on
the web pages of "Cosmic Ancestry" -- part of the Panspermia website,
devoted to research and conjecture about the spread of life between star
systems.

Even to the un-trained eye the objects in the pictures look like
organisms.

"Since these objects look so much like the remains of terrestrial
organisms, it seems most likely that they are remains of terrestrial
organisms," said Allan Treiman from the Lunar and Planetary Institute
in Houston. "Terrestrial bacteria and fungi infest meteorites almost
immediately on landing on Earth, take up residence and consume whatever
they can. The fungi worm their way into the meteorites along cracks and
pores, and 'burrow' into the carbonaceous material as they eat it".

Treiman has also been critical of the claims about microfossils in the
famous martian meteorite ALH84001.

Dr Andrew Steele from the University of Portsmouth told SPACE.com
"meteorites become contaminated with Earth life within days of landing,
yet some of the Murchison meteorites were in the open for four to five
months before being collected."

Added Steele, "electron microscopes and morphology [comparing the shape
of organisms] are powerful tools, but they are not conclusive. More
detailed biological tests of other meteorite specimens point in one
direction -- terrestrial microbial contamination."

Last year Steele found evidence of infestation by fungi and bacteria in
another piece of Murchison meteorite. Crystals had even started to grow
over some of the microbes while the rocks had been in storage. In more
extreme cases this mineral growth could possibly be mistaken for
fossils.

Dr Matthew Genge, a meteorite researcher from the Natural History Museum
in London, is also skeptical.

"Murchison meteorites are even more likely than most to have experienced
contamination since they fell in a farmyard and, reputedly, at least
some of the stones had to be recovered from a ditch filled with manure,"
Genge said, adding that "any meteorite recovered outside Antarctica has
had ample opportunity to become contaminated. Those in museum
collections have furthermore been handle many times."

Treiman wrapped up the case for the negative: "my opinion [for what its
worth] is that the meteorites are infested with Earth bacteria -- the
meteorites are not infested with extraterrestrial bacteria. The issue of
life in the solar system is fascinating, but [like all good detective
stories] will have lots of false leads."

c2000 Space.com

References for this article are at
http://www1.tpgi.com.au/users/tps-seti/reading.html#ez8b

===============
(7) DEGRADATION SIGNATURES AROUND IMPACT CRATERS

J.A. Grant: Evaluating the evolution of process specific degradation
signatures around impact craters. INTERNATIONAL JOURNAL OF IMPACT
ENGINEERING, 1999, Vol.23, No.1 Pt1, pp.331-340

SUNY COLL BUFFALO,1300 ELMWOOD AVE,BUFFALO,NY,14222

The pristine morphologies created during an impact event comprise a
template for constraining how various environmental parameters
influence the mechanics of crater formation. Identification of
pristine morphologies used in defining and/or evaluating models of
crater formation can be complicated or precluded however, by the
effects of post-formation degradation.. Field and/or remote
examination of simple, unglaciated impact craters on the Earth (e.g.,
Meteor Crater, Arizona, and Roter Kamm crater, Namibia) can yield
results that help to define characteristic degradation signatures for
use in placing first-order constraints on the number and intensity of
processes that have been active. In turn, the presence of a suite of
these degradation signatures can be used to define the amount and
style of crater degradation that has taken place, thereby providing a
tool for possible distinction between pristine versus secondary,
post-formation characteristics. (C) 1999 Elsevier Science Ltd. All
rights reserved.Copyright 2000, Institute for Scientific Information
Inc.

===============
(8) IMPACT CRATERS IN 3D

D. Wallis*), C.J. Solomon, L. Kay: Use of Scanning Electron Microscopy
for three dimensional stereo analysis of impact craters and modelling
with Zernike polynomials. ADVANCES IN SPACE RESEARCH, 1999, Vol.25,
No.2, pp.339-344

*) UNIVERSITY OF KENT,UNIT SPACE SCI & ASTROPHYS,CANTERBURY CT2
   7NR,KENT,ENGLAND

Examples will be presented to demonstrate the use of a Scanning
Electron Microscope to obtain detailed measurements of hypervelocity
impact craters and to obtain the shapes of craters in three dimensions
by comparing stereo pairs. The depth of each crater is sampled at
approximately 5000 points and the data is fitted using a set of
polynomials orthogonal over a unit disc ( the Zernike polynomials). The
specific application to be presented is the study of groups of craters
produced under identical impact conditions by firing a quantity of
projectiles as buckshot from a light gas gun. Analysis of the Zernike
polynomial spectrum of the crater shapes will show quantitatively the
variations in crater shapes, both within groups of identical craters
and between groups corresponding to different impact conditions. In
this way the potential of the method for inferring properties of
impactors will be assessed, with the aim of applying the method to
obtain velocity and density information from craters in retrieved
space-exposed surfaces. (C) 1999 COSPAR. Published by Elsevier Science
Ltd.

==================
(9) JAPANESE CONTRIBUTION TO METEOROID & SPACE DEBRIS   
    MEASUREMENT

H. Yano: Japanese contribution to in-situ meteoroid and debris
measurement in the near Earth space. EARTH PLANETS AND SPACE, 1999,
Vol.51, No.11, pp.1233-1246

INST SPACE & ASTRONAUT SCI,PLANETARY SCI DIV,3-1-1
YOSHINODAI,SAGAMIHARA,KANAGAWA 229851,JAPAN

This paper reviews major results of present studies and recent
developments for future missions in the Japanese space program
regarding in-situ measurement and collection of micrometeoroids
and orbital debris in the near Earth space. Japan's contribution in
this area began with the post flight impact analysis of the Space
Flyer Unit (SFU) satellite which was returned to Earth in 1996 after
10-month exposure in space. Despite a decade later than similar
efforts first conducted in the USA and Europe, it resulted in a
record of over 700 hypervelocity impact signatures, which now forms
the nation's first database of real space impacts being open to
public in the Internet. Together with laboratory impact tests, both
morphological and elemental analyses of the impact craters yielded
new insights of the meteoroid to debris ratio as well as flux
variation compared with the previous spacecraft. The next step was a
passive aerogel exposure in the STS-85 shuttle mission in 1997. No
hypervelocity impact was found there but its experience has been
incorporated for designing a microparticle collector to be on-board
the Japan Experiment Module-Exposed Facility of the International
Space Station. All of such ''passive'' collection of micro-impact
features, however, still leave the significant uncertainty in the
quest of their origins. Therefore an aerogel-based ''hybrid'' dust
collector and detector (HD-CAD) is currently under the development.
It measures time of impact and deduces impactors' orbital and
physical parameters by detecting impact flash while still capturing
them intact. The system is suitable for both (1) sample return
missions in LEO as well as to parent bodies of meteoroids, i.e.,
comets and asteroids, and (2) one-way mission to where the thermal
and plasma environment is such that impact induced plasma detectors
may suffer from significant noise, e.g., a Mercury orbiter and a
solar probe. Together with unambiguous dust samples from a comet by
STARDUST and an asteroid by MUSES-C as references, the HD-CAD in the
LEO will be able to deduce the accretion rates of the cometary and
asteroidal dust grains on the Earth. Copyright 2000, Institute for
Scientific Information Inc.

===========================
* LETTERS TO THE MODERATOR *
=============================

(10) POSSIBLE CAUSES OF CYCLICAL IMPACT EVENTS

From Michael Rampino <mrr1@is3.nyu.edu>

Benny:

A nice up-to-date discussion of the possible causes of cyclic impacts
and extinctions is given by John and Mary Gribbin in their book "Fire
on Earth (St. Martin's Press, New York, 1996; see Chapter 8, Cycles of
Doom).

After reviewing the evidence, they conclude that it makes: "the
galactic carousel is our best buy to account for the 30 Myr cycle of
death."

Mike Rampino

Dr. Michael R. Rampino
Earth & Environmental Sciences Program, New York University, 100
Washington Square East, Rm. 1009, New York, NY 10003
212-998-3743; 212-995-3820 (fax)
and NASA, Goddard Institute for Space Studies, 2880 Broadway, New York, NY
10025. mrampino@giss.nasa.gov

===========
(11) RUMOURS AND ALLEGATIONS

From Jeremy Tatum <UNIVERSE@uvvm.UVic.CA>

What is the matter with solar system scientists these days? We used to
do astronomy because we enjoyed it. Nowadays the field seems all too
full of people who seem to make it their business to find fault with
the efforts of others, by making unfounded allegations and spreading
rumours about the personal deficiencies of colleagues, and keeping it
up for month after month. Anyone will be able to think of recent
examples. Yet another one turned up in today's peisergrams. This time a
"source" explained "privately" to UPI that an "unnamed space official"
had altered something or other, and it was therefore someone's fault
that the Mars Polar Lander failed. Such rumours about unnamed persons
by unnamed persons should be ignored and I am surprised that they would
be further distributed in a peisergram.

Exploring planets by spacecraft is an enormously difficult undertaking,
and there are certain to be failures along the way, and probably many
of them. Certainly when there is a failure, there needs to be an
enquiry to determine its cause, whether by human failure or not - but
anonymous accusations of wrongdoing and of coverups (whether in this
instance or in others that will doubtless come to mind) are about as
unhelpful as it is possible to imagine.

No one and no organization is beyond constructive criticism, but to
anyone who feels he has to find fault with a failed spacecraft
excursion to a distant planet I would just say: "Well, you go ahead and
do it, and show us how it ought to be done."

Jeremy Tatum

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