CCNet 3/2001 - 5 January 2001

"Exploding meteors bombarding the Earth from space could be mistaken
for nuclear bomb tests, say seismologists of the Royal Netherlands
Meteorological Institute. This could present problems for monitoring the
Comprehensive Nuclear Test Ban Treaty (CTBT), which aims to halt the
testing of all nuclear weapons."
   -- Philip Ball, Nature, 5 January 2001

"The beginning of the Dark Ages may have been literal, as well as
figurative, as the result of a massive volcanic eruption in the 6th
century, according to a volcanologist at the Department of Energy's Los
Alamos National Laboratory. Ken Wohletz said an eruption in the
Indonesian archipelago could have produced a 150-meter-thick cloud layer
over the entire Earth, triggering a chain of climatic, agricultural,
political and social changes that ushered in the Dark Ages."
   -- John Webster, Los Alamos National Laboratory

"Hyper-hyperbole. It's massive!"-- article title in the UK newspaper
The Observer, Feb. 27, criticizing news media which make exaggerated claims
to bolster their arguments.
"It's apocalypse now as world boils over."-- headline in the same
newspaper, same day.
   -- Congratulations to the UK winner of The Dubious Data 2000

    Andrew Yee <>

    Ron Baalke <>


    David Morrison <>

    ESA News <>

    Los Alamos National Laboratory

    Duncan Steel <>

    James Oberg <>

    J. Tate

     D.G. Korycansky et al.

     L.R.B. Rubio et al.

     L.R.B. Rubio et al.

     R.A. Craddock & A.D. Howard

     R.R. Herrick & V.L. Sharpton

     A.T. Basilevsky et al.

     A.J. Dombard & W.B. McKinnon

     W. Flury et al.

     Statistical Assessment Service, 1 January 2001


From Andrew Yee <>

From Nature Science Update, 5 January 2001
[ ]

Friday, 5 January 2001
Meteors come in with a bang

Exploding meteors bombarding the Earth from space could be mistaken for
nuclear bomb tests, say seismologists of the Royal Netherlands
Meteorological Institute. This could present problems for monitoring the
Comprehensive Nuclear Test Ban Treaty (CTBT), which aims to halt the testing
of all nuclear weapons.

Läslo Evers and Hein Haak detected a sonic boom from a meteor explosion with
an instrument similar to those currently under construction for verification
of the CTBT.

The explosion released energy equivalent to 1.5 kilotons of TNT, the
researchers calculate. This is as big a bang as was made by several of the
US nuclear tests of the early 1960s, and at the lower end of the estimated
size of the Pakistani tests of 1998.

The future of the CTBT has been under a cloud since the US Senate decided
not to ratify it in 1999. But many other nations have already done so, and
plans are afoot for global detection systems that will alert the
international community to secret nuclear weapons tests.

Underground tests send out shock waves that seismic monitoring stations
designed for earthquake detection can pick up. And atmospheric tests create
a kind of low-frequency ('infrasound') sonic
boom which highly sensitive air-pressure meters (microbarometers) can
register. A worldwide network of 60 infrasound detectors is being built for
this purpose.

Situated near the village of Deelen in the Netherlands, the instrument Evers
and Haak used is not designated for CTBT verification -- it is primarily a
meteorological device. But in November 1999, it registered a most unusual

At around four o'clock in the morning of the 8th November, a few early
risers in Germany and the Netherlands saw a flash in the dark sky above
northern Germany. A meteor -- a small chunk of space rock plunging through
the atmosphere -- had exploded at a height of about 20 kilometres.

The event was similar to a better-documented one that occurred in the middle
of the afternoon over New Zealand the previous July. On that occasion,
observers reported "a bright light, exactly like a flare", variously
described as blue, red, orange or yellow. It was followed by a loud boom,
and left behind a puff of brown smoke.

About one meteor detonates in the atmosphere every week. Most go unseen by
human eyes, as they break apart very high in the sky. Only rarely does one
strike or explode close to the planet's surface, such as the object that
levelled trees over hundreds of square kilometres in Tunguska, Siberia, in

That event aside, the height of these explosions usually hides their
tremendous ferocity. The explosion of November 1999 showed up on the Deelen
microbarometer as an infrasound blip slightly greater than the background
noise generated by ocean waves, which create a constant barrage of small
atmospheric booms called microbaroms.

Reported in the journal Geophysical Research Letters [1], Evers and Haak's
research highlights how crucial it will be for an infrasound network to be
able to distinguish between meteor explosions and genuine nuclear blasts.

[1] Evers, L. G. & Haak, H. W. Listening to sounds from an exploding meteor
and oceanic waves. Geophysical Research Letters 28, 41-44 (2001).

© Macmillan Magazines Ltd 2000 - NATURE NEWS SERVICE


From Ron Baalke <>

Jet Propulsion Laboratory
January 3, 2001

Millennium Asteroid Greets New Year

NASA's Near Earth Asteroid Tracking System (NEAT), operated by JPL,
discovered the first asteroid of the new millennium on Jan. 1. This is 200
years after the discovery of Ceres, the first and largest asteroid ever
discovered. NEAT scientists compare snapshots of the same parts of the sky
to find moving objects, which may be small or faint.

Image of the asteroid available here:

From the NEAT home page (


2001 AA = MBTR3F

NEAT discovered the first asteroid of the new millennium on 1 January 2001.
This is 200 years to the day after the discovery of Ceres, the first and
largest asteroid. 2001 AA is a Mars-approaching asteroid, about 1.5 km (1
mile) in size. A visualization is provided from a preliminary orbital
solution (K. Lawrence, JPL):



Don Savage
Headquarters, Washington, DC                January 4, 2001
(Phone:  202/358-1727)

RELEASE: 01-01


It's a difficult decision: With about $300 million to spend, should NASA buy
a spacecraft that could find Earth-sized planets around nearby stars? What
about a mission that could peer deep
inside Jupiter's gaseous atmosphere? Or should the agency go with a mission
to orbit the two largest asteroids in the solar system?

The answer to that question will have to wait about a year. In the first
step of a two-step process, NASA's Office of Space Science selected three
proposals for detailed study as candidates for the next mission in the
agency's Discovery Program of lower cost, highly focused, rapid-development
scientific spacecraft.

"The diversity of science represented in these three mission proposals is
outstanding. NASA will have its hands full picking only one for flight,"
said Dr. Jay Bergstralh, acting Director of Solar System Exploration at NASA
Headquarters, Washington, DC.

The selected proposals were judged to have the best science value among 26
proposals submitted to NASA last August. Each selected team will receive
$450,000 to conduct a four-month implementation-feasibility study focused on
cost, management and technical plans, including educational outreach and
small business involvement.

Following detailed mission concept studies, NASA intends to select one of
the three proposals late in 2001 for full development. The mission should be
launched around 2005 or 2006.

NASA has also decided to fund American participation in a mission to Mars
being flown by another nation. In this "Mission of Opportunity" NASA will
contribute to seismology, meteorology and
geodesy (to measure the size and shape of the planet) experiments on the
French-led NetLander Mission, scheduled for launch in 2007. The Mission of
Opportunity team will receive $250,000 to conduct its feasibility study.

The selected Discovery and Mission of Opportunity proposals are:

*  The Kepler mission is a space telescope specifically designed to detect
Earth-sized planets around stars in the Sun's neighborhood of the galaxy. By
monitoring 100,000 stars over a
four-year mission, Kepler could detect up to 500 Earth-sized planets and up
to 1000 Jupiter-sized planets. Dr. William Borucki of NASA's Ames Research
Center at Moffet Field, CA, would lead Kepler at a total cost to NASA of
$286 million.

*  The Interior Structure and Internal Dynamical Evolution of Jupiter
(INSIDE Jupiter) mission is a Jupiter orbiter designed to observe and
measure processes occurring within the Jovian magnetosphere and atmosphere.
INSIDE Jupiter would determine the internal structure of the planet by
obtaining high resolution maps of the magnetic and gravity fields. Dr.
Edward J. Smith of the Jet Propulsion Laboratory in Pasadena, CA, would lead
INSIDE Jupiter at a total cost to NASA of $296 million.

*  The Dawn mission intends to orbit Vesta and Ceres, two of the largest
asteroids in the solar system. According to current theories, the very
different properties of Vesta and Ceres are the result of the asteroids
being formed and evolving in different parts of the solar system. By
observing both asteroids with the same set of instruments, Dawn would probe
the early solar system as well as determine in detail the properties of each
asteroid. Dr. Christopher T. Russell of the University of California at Los
Angeles would lead Dawn at a total cost to NASA of $271 million.

*  A U.S. contribution to the French-led NetLander mission will add unique
capabilities to each of the four landers and the orbiter which comprise the
mission. In 2007, NetLander will create the first science network on Mars to
study the planet's internal structure. The American contribution includes
short period seismometers and wind sensors on the landers, and a
high-resolution geodesy instrument on the orbiter. Dr. W. Bruce Banerdt of
the Jet Propulsion Laboratory will lead the U.S. contribution to NetLander
at a total cost to NASA of $35 million.

The Discovery Program is designed to provide frequent, low-cost access to
space for planetary missions and missions to search for planets around other
stars. The selected science missions must be ready for launch before
September 30, 2006, within the Discovery Program's cap on each mission's
cost to NASA of $299 million.

The Discovery Program is managed at NASA's Jet Propulsion Laboratory, a
division of the California Institute of Technology, Pasadena, for the Office
of Space Science, Washington, DC. More information on the Discovery Program
is available at: 



From David Morrison <>


by Richard P. Binzel (MIT)

I wanted to share with you that I had the opportunity to raise a toast of
Sicilian wine to Giuseppe Piazzi at 8 pm Palermo time on the evening of
January 1. The location of the toast was inside the dome of the Palermo
Observatory where the refurbished transit circle was recently re-installed.
All parts of the transit circle are original to the time of Ceres'
discovery, exactly 200 years earlier, except for the eyepiece which was
apparently discarded when it was replaced in the mid-nineteenth century.

Attendance at the commemorative talks included members of the Piazzi family
still living in the same house in Ponte Valtellina (northern Italy) where
Giuseppe Piazzi was born in 1746. The mayor of Ponte Valtellina was also in
attendance and conveyed his greetings. The post office of Palermo issued a
special "Centenario Della Scoperta di Cerere" postmark dated 1.1.2001.
Invited talks included a description of the design and acquisition of the
Palermo transit circle, given by Professor Giorgia Fodera' Serio (U.
Palermo), an account of Piazzi and his Paris colleagues by Suzanne Debarbat
(Obs. Paris), and a description of Jesse Ramsden's London workshop - where
the Palermo circle was made - given by Anita McConnell (U. K.). The final
talk of the evening was my own "Asteroids Coming of Age" (see Science 289,
2065) revealing how asteroids had come to earn their current level of
scientific respect (with great credit to T. Gehrels and G. Shoemaker).

The Palermo Observatory Director, Professor Salvatore Serio, presented to
the members of the Piazzi family copies of the original congratulatory medal
offered to Giuseppe Piazzi following his discovery. Interestingly, Giuseppe
Piazzi turned down the original medal so that those funds be used to
purchase additional instrumentation for the Observatory. It was a thrill and
an honor for the current generation of the Piazzi family to finally accept
the medal on behalf of their distant relative.


From ESA News <>

Astronomers have so far detected about 50 planets orbiting other stars. They
are all giant, Jupiter-like planets, made mostly of gas, and their formation
process is still unclear. ESA's Infrared Space Observatory, ISO, now sheds
some light on this problem.

More at:


From Los Alamos National Laboratory

CONTACT: John Webster,, 505-667-5543 (00-165)

The dark ages may have really been dimmer

LOS ALAMOS, N.M., Dec. 17, 2000 -- The beginning of the Dark Ages may have
been literal, as well as figurative, as the result of a massive volcanic
eruption in the 6th century, according to a volcanologist at the Department
of Energy's Los Alamos National Laboratory.

Ken Wohletz said an eruption in the Indonesian archipelago could have
produced a 150-meter-thick cloud layer over the entire Earth, triggering a
chain of climatic, agricultural, political and social changes that ushered
in the Dark Ages.

Evidence supporting the catastrophe includes tree-ring and ice-core
measurements, indications of a huge underwater caldera, and ash and pumice
in the same area, said Wohletz, who discusses his work modeling such an
eruption today (Dec. 17) at the fall meeting of the American Geophysical

The 6th century was a turbulent, unsettling period in human history. The
Roman Empire began to fall; nomads of central Asia migrated to Europe and
the Near East; civilizations in Persia, Indonesia and South America
collapsed; major religions experienced considerable change as natural events
were viewed as omens.

Many of these social transformations resulted from widespread crop failures
and the explosion of plague around the globe, which in turn were caused by
major climatic changes, Wohletz said. Beginning in about the year 535,
according to historical and archeological records, the weather was colder
and drier, sunlight diminished, snow fell in summer and regions of
persistent drought suffered floods.

Wohletz was a resource for a book postulating that the climate changes
resulted from a huge volcanic eruption. The book, "Catastrophe: A Quest for
the Origins of the Modern World" by David Keys, was published earlier this

Wohletz said he worked with Keys to try to identify a volcano that could
produce such dramatic climate change. "We came up with an eruption that
would certainly be the largest in recorded history, some four or five times
bigger than the (1815) eruption of Tambora, which is usually considered the
biggest eruption in the past few millennia," he said.

Such an explosion, he said, would eject some 200 cubic kilometers of
material, and one-third to one-half of it would be lofted into the
stratosphere, where it would remain suspended for months to years while
being carried around the globe.

"It would have produced enough dust and water vapor (in the form of ice
crystals) to form a cloud layer 150 meters thick over the entire globe, and
that's a conservative estimate," he said, adding that a cloud of particles
that thick may have diminished the transmission of sunlight by as much as 50

Wohletz said tree-ring data collected around the world and ice-core
measurements in Greenland and Antarctica support the possibility of a huge
eruption in the 6th century. Ocean depth measurements between Sumatra and
Java ­ where Krakatoa exploded in a well known 1883 eruption ­ indicate the
presence of a caldera up to 50 kilometers in diameter, and a recent survey
uncovered evidence of ash and pumice layers formed in the area during the
appropriate time frame.

Under a likely scenario, a large volcano, which Wohletz calls
proto-Krakatoa, connected the islands of Sumatra and Java. When it erupted
and then subsided, it created the Sundra Strait and left a ring of smaller
volcanoes, including the present day Krakatoa. The ash, dust and water vapor
blown into the stratosphere would disperse across both the Northern and
Southern Hemispheres.

"This volcano would have had the potential to be a major player in
destabilizing the climate around the world," he said. "An eruption that
could produce a caldera 50 kilometers across would have been big enough."

Although definitive evidence for such a catastrophic eruption has not been
discovered, the possibility deserves a full-scale field study, Wohletz said,
in part because of the potential impact on the world if another such
catastrophe happens.

"(Key's book) is the first detailed account of how closely humanity is
linked to the natural world," he said. "If the natural world goes through
some large upheaval, we'll all be affected."

Los Alamos National Laboratory is operated by the University of California
for the U.S. Department of Energy.


From Duncan Steel <>

Total Lunar Eclipse on Tuesday January 9th

Essential points:

Moon enters the Earth's shadow at 18:42
Totality begins at 19:49
Totality ends at 20:51
Moon leaves the Earth's shadow at 21:59

The entire eclipse sequence is visible from throughout the U.K. This is the
last such event to be seen from the U.K. until November 2003

See my book Eclipse (*paperback* edition of July 2000), p.54 in particular.

The diagram given there comes from:

Duncan Steel


From James Oberg <>

Re CCNet 1/4/01: SIZZLING SKIES: << And there are even unconfirmed reports
that the space shuttle returns to Earth with an electrophonic crackle. >>

"Unconfirmed" indeed! I collected dozens of eyewitness accounts from shuttle
entries over Texas  in 1984-5 and forwarded them to Keay. We even went out
during one fireball fly-over with antennas to record the EM pulse. There are
fewer opportunities now because the required orbit (28 degrees) and landing
site (KSC in Florida) are rarely used together since most missions are to
the northerly orbit of the Mir or International Space Station, so the flyovers
are either across the American midwest or across the Yucatan penninsula,
where we don't have any experienced observers.

Jim Oberg


J. Tate: Avoiding collisions: the Spaceguard Foundation. SPACE POLICY 16:
(4) 261-265 NOV 2000

The Earth has a long and violent history of collisions with extraterrestrial
bodies such as asteroids and comet nuclei. Several of these impacts have
been large enough to produce major environmental changes, causing mass
extinctions and severe alterations to weather patterns and geography. There
is no reason to suppose that the likelihood of such collisions will be any
less in the future and the spread of human settlement, civilisation, and
particularly urbanisation, makes it much more likely that a future impact,
even relatively small, could result in the massive loss of human life and
property. Despite the fact that the technology exists to predict and to some
extent prevent such events, there is currently no co-ordinated international
response to this threat. This article presents a realistic assessment of the
threat to Earth from NEOs, describes the (underfunded) efforts so far made
to counter it and makes a plea for further action to produce a fully
functioning Spaceguard Foundation. (C) 2000 Published by Elsevier Science

Tate J, Spaceguard UK, Cygnus Lodge, High St, Salisbury SP4 8JT, Wilts,
Spaceguard UK, Salisbury SP4 8JT, Wilts, England.

Copyright © 2001 Institute for Scientific Information


Korycansky DG, Zahnle KJ, Law MMM: High-resolution calculations of asteroid
impacts into the venusian atmosphere
ICARUS 146: (2) 387-403 AUG 2000

We present results from a number of 2D high-resolution hydrodynamical
simulations of asteroids striking the atmosphere of Venus. These cover a
wide range of impact parameters (velocity, size, and incidence angle), but
the focus is on 2-3 km diameter asteroids, as these are responsible for most
of the impact craters on Venus. Asteroids in this size range are
disintegrated, ablated, and significantly decelerated by the atmosphere, yet
they retain enough impetus to make large craters when they meet the surface.
We find that smaller impacters (diameter <1-2 km) are better described by a
"pancaking" model in which the impactor is compressed and distorted, while
for larger impacters (>2-3 km) fragmentation by mechanical ablation is
preferred. The pancaking model has been modified to take into account
effects of hydrodynamical instabilities. The general observation that most
larger impacters disintegrate by shedding fragments generated from
hydrodynamic instabilities spurs us to develop a simple heuristic model of
the mechanical ablation of fragments based on the growth rates of
Rayleigh-Taylor instabilities. Although in principle the model has many free
parameters, most of these have little effect provided that they are chosen
reasonably. In practice the range of model behavior can be described with
one free parameter. The resulting model reproduces the mass and momentum
fluxes rather well, doing so with reasonable values of all physical
parameters. (C) 2000 Academic Press.

Korycansky DG, Univ Calif Santa Cruz, Univ Calif Observ, Lick Observ, Santa
Cruz, CA 95064 USA.
Univ Calif Santa Cruz, Univ Calif Observ, Lick Observ, Santa Cruz, CA 95064
NASA, Ames Res Ctr, Moffett Field, CA 94035 USA.
Amer Museum Nat Hist, Dept Astrophys, New York, NY 10024 USA.


Rubio LRB, Ortiz JL, Sada PV: Observation and interpretation of meteoroid
impact flashes on the moon
EARTH MOON AND PLANETS 82-3: 575-598 2000

The first unambiguous detection of meteoroids impacting the night side of
the Moon was obtained during the 1999 Leonid storm. Up to eight optical
flashes were recorded with CCD video cameras attached to small telescopes on
November 18, 1999. Six impacts were videotaped by at least two independent
observers at the same times and lunar locations, which is perhaps the
strongest evidence for their collisional nature. The flashes were clearly
above the noise and lasted for less than 0.02 s. Although previous
observational efforts did not succeed in detecting impact flashes,
additional candidates have been reported in the literature. The evidence
accumulated so far implies that small telescopes equipped with high speed
cameras can be used as a new tool for studying meteoroid streams, sporadic
meteoroids, and hypervelocity collisions. In this review we discuss the
various intervening parameters for detectability of flashes on the night
side of the Moon (geometrical effects, contamination by scattered light from
the day side, and properties of the meteoroids such as speed and flux of
particles). Particular emphasis is placed on the analysis of the
observations in order to derive relevant physical parameters such as
luminous efficiencies, impactor masses, and crater sizes. Some of these
parameters are of interest for constraining theoretical impact models. From
a simple analysis, it is possible to derive the mass distribution of the
impactors in the kg range. A more elaborate analysis of the data permits an
estimate of the fraction of kinetic energy converted to radiation (luminous
efficiency) if the meteoroid flux on the Moon is known. Applied to the 1999
lunar Leonids, these methods yield a mass index of 1.6 +/- 0.1 and luminous
efficiencies of 2 x 10(-3) with an uncertainty of about one order of
magnitude. Predictions of visibility of the major annual meteor showers are
given for the next few years. These include the forthcoming 2001 Leonid
return, for which we estimate detection rates in the visible.

Rubio LRB, Inst Astrofis Canarias, Tenerife, Spain.
Inst Astrofis Canarias, Tenerife, Spain.
CSIC, Inst Astrofis Andalucia, Granada, Spain.
Univ Monterrey, Monterrey, Mexico.

Copyright © 2001 Institute for Scientific Information


Rubio LRB, Ortiz JL, Sada RV: Luminous efficiency in hypervelocity impacts
from the 1999 lunar Leonids
ASTROPHYSICAL JOURNAL 542: (1) L65-L68, Part 2 OCT 10 2000

An analysis of the optical flashes produced by Leonid meteoroids impacting
the Moon in 1999 November is carried out in order to estimate the fraction
of kinetic energy converted into radiation, the so-called luminous
efficiency eta. It is shown that the observational data are consistent with
luminous efficiencies of 2 x 10(-3) in the wavelength range of 400-900 nm
with an uncertainty of about 1 order of magnitude. This experimental value
of eta is significantly larger than previous estimates for meteoroids of
asteroidal composition based on numerical calculations and scaling laws from
laboratory collisions. According to our results, the luminous efficiency
might vary with mass, i.e., the smaller impactors converting less kinetic
energy into light and vice versa. A comparison with recent numerical
simulations for meteoroids of cometary composition is also carried out.

Rubio LRB, Inst Astrofis Canarias, Via Lactea, E-38200 La Laguna, Canary
Islands, Spain.
Inst Astrofis Canarias, E-38200 La Laguna, Canary Islands, Spain.
CSIC, Inst Astrofis Andalucia, E-18080 Granada, Spain.
Univ Monterrey, Dept Fis & Matemat, Monterrey 66238, Nuevo Leon, Mexico.

Copyright © 2001 Institute for Scientific Information


Craddock RA, Howard AD: Simulated degradation of lunar impact craters and a
new method for age dating farside mare deposits

With the advent of Clementine data it is now possible to determine the
lithology and extent of geologic materials on the Moon, particularly the
farside mare deposits. However, traditional crater counting techniques do
not provide reliable age estimates of these materials owing to their small
surface areas, To support such studies, we present a model for estimating
their age by analyzing the morphometry of degraded craters 1-3 km in
diameter. A photoclinometric model was adapted for use with monoscopic
0.750-mu m ultraviolet-visible and high-resolution images where we extracted
the topography of fresh craters. A two-dimensional computer model simulating
linear diffusional creep was applied to fresh craters at a variety of
diameters. The resulting profiles were then compared to photoclinometric
profiles of degraded craters of known ages for calibration. Application of
the resulting model to degraded craters in the mare deposit of the central
Apollo basin (-36.5 degrees latitude, 208.0 degrees longitude) indicates
that this material was emplaced during the early Imbrian period (similar to
3.85 Ga). By calculating the amount of material eroded from each of the
degraded craters observed in this unit, the average erosion rate is
estimated to be 2.0+/-0.1 x 10(-7) mm/yr on the Moon since the Imbrian. The
estimated amount of material eroded during any given period suggests that
the erosion rate has decreased with time, implying that the flux of larger
impactors has as well.

Craddock RA, Smithsonian Inst, Natl Air & Space Museum, Ctr Earth &
Planetary Studies, Room 3776, MRC-315, Washington, DC 20560 USA.
Smithsonian Inst, Natl Air & Space Museum, Ctr Earth & Planetary Studies,
Washington, DC 20560 USA.
Univ Virginia, Dept Environm Sci, Charlottesville, VA 22903 USA.

Copyright © 2001 Institute for Scientific Information


Herrick RR, Sharpton VL: Implications from stereo-derived topography of
Venusian impact craters

Using radargrammetry we have created high-resolution topographic maps of 74
Venusian craters, including all blight-floured craters over 12 km in
diameter covered by Magellan stereo imagery, Our trend for rim-floor depths
RF as a function of diameter D for bright-floored craters in the volcanic
plains is RF = (0.3450.05) D0.2350.05, and for dark-floored craters in the
plains, RF = (0.50.1) D0.0350.07. Rim heights RH for bright-floored craters
in the plains are RH = (0.060.03) D0.40.2 (D > 15 km), and for dark-floored
craters in the plains, RH = (0.0270.015) D0.40.2. These trends indicate that
bright-floored craters 30 km in diameter are, on average, deeper than
dark-floored craters by 180 m from rim to floor and have a 140 m higher rim,
and at 90 km in diameter they are 380 m deeper from rim to floor and have a
220 m higher rim. The bright- and dark-floored populations ale different at
a 99% confidence level for both rim-flour depths and rim heights. The
interpretation most consistent with our data and previous work by others is
that Venusian craters with radar-dark floors have been partially filled and
had their ejecta blankets embayed by regional-scale lava flooding. When the
topography is examined in conjunction with the imagery, it is clear that
many dark-floored craters have been surrounded by lavas that rose neatly to
the crater rim even though a substantial portion of the crater's ejecta
blanket was retained. Most previous analyses of the resurfacing history of
Venus have relied on past interpretations that only a small percentage of
Venusian craters are embayed by exterior volcanism. Because most craters on
Venus have dark floors, our data indicate that the majority of Venusian
craters have been surrounded and partially filled by postimpact lavas, and
consequently, those previous analyses may have significantly underestimated
the amount of volcanism on the Venusian surface over the past few hundred
million years. Rim-floor depths for Venusian craters are consistent with the
inverse gravity trend observed for the terrestrial planets, and they are
similar to 50% deeper than current estimates for complex craters on the
Earth. Unlike the other terrestrial planets, neither terrain-floor depths
nor central structure heights increase with increasing crater diameter. An
interesting trend fur which we have no explanation is that on Venus, the
Moon, Mars, and Ganymede, central peaks generally rise to within a constant
elevation relative to the surrounding ten ain, but that elevation is lower
on the Moon and Mars than on Venus and Ganymede.

Herrick RR, Univ Alaska Fairbanks, Inst Geophys, POB 75732, Fairbanks, AK
99775 USA.
Univ Alaska Fairbanks, Inst Geophys, Fairbanks, AK 99775 USA.

Copyright © 2001 Institute for Scientific Information


Basilevsky AT, Ivanov MA, Kryuchkov VP: On the degradation of impact craters
on Callisto
SOLAR SYSTEM RESEARCH 34: (4) 277-284 JUL-AUG 2000

The impact-crater population on Jupiter's satellite Callisto was studied
with the use of two Galileo images. It is found that craters with diameters
below similar to 1 km are bowl-shaped, like similar-sized impact craters on
the Moon, and the morphological degradation of these craters proceeds in the
way typical of small lunar craters: their contours become less prominent.
Larger craters on Callisto vary from bowl-shaped to flat-floor and, further,
to central-peak, like their lunar counterparts. However, these craters on
Callisto differ radically from the lunar ones in that their degradation
proceeds by fragmentation of their rims. An average cumulative density of
raters 1 to 32 km across in the two examined regions of Callisto is
described by the equation N->D = 0.03D(-1.6), and the densities of craters
from 5.7 to 32 km in diameter on Callisto and on the farside of the Moon are
nearly the same. Our studies give grounds to believe that most of the impact
craters above similar to 1 km in diameter were formed late in the period of
heavy meteoritic bombardment. On Callisto, not only was the formation of
craters intensive at that time, but also an approximate balance had been
reached between formation and degradation. Sublimation of the icy component
of the Callistan "crust" probably made a major contribution to the crater
degradation. The conditions on Callisto during this period were possibly
different from the present-day ones. Frequent falls of meteoroids on
Callisto might have led to the formation of a temporary atmosphere. Under
such conditions, the landform degradation could proceed not only by
sublimation of CO2 ice (as suppose Moore ct al., 1999) but also by
sublimation and even melting of water ice and possibly other icy components.
New meteorite impacts and down-slope movement of the surface material were
of secondary importance in the crater degradation during this period. When
the period of heavy meteorite bombardment ended, the development of
large-scale relief on Callisto virtually ceased. Only the formation of small
impact craters and their slow evolution following the lunar pattern
continued for the most part.

Basilevsky AT, VI Vernadskii Inst Geochem & Analyt Chem, Ul Kosygina 19,
Moscow 117975, Russia.
VI Vernadskii Inst Geochem & Analyt Chem, Moscow 117975, Russia.

Copyright © 2001 Institute for Scientific Information


Dombard AJ, McKinnon WB: Long-term retention of impact crater topography on
GEOPHYSICAL RESEARCH LETTERS 27: (22) 3663-3666 NOV 15 2000

Previous analyses into viscous relaxation of impact craters on Ganymede have
predicted short characteristic relaxation times (of the order of 100 Myr or
less for larger craters), in disagreement with the apparent great ages of
Ganymede's terrains. By applying improved understanding of theologic
parameters and initial crater shapes to a viscoelastic model, we calculate
upper limit (zero heat flow) relaxation times in excess of the age of the
solar system, eliminating this discrepancy. These very long relaxation times
are not due to elastic effects, but are simply due to the effective
viscosity of water ice at the appropriate temperatures and stresses.

Dombard AJ, Carnegie Inst Washington, Dept Terr Magnetism, 5241 Broad Branch
Rd NW, Washington, DC 20015 USA.
Washington Univ, Dept Earth & Planetary Sci, St Louis, MO 63130 USA.
Washington Univ, McDonnell Ctr Space Sci, St Louis, MO 63130 USA.

Copyright © 2001 Institute for Scientific Information


Flury W, Massart A, Schildknecht T, Hugentobler U, Kuusela J, Sodnik Z:
Searching for small debris in the geostationary ring - Discoveries with the
Zeiss 1-metre telescope

More than 800 satellites and rocket upper stages have been inserted into the
geostationary ring or its vicinity over the years, but only about 250 to 270
of these satellites are currently being used operationally. Geostationary
satellites are therefore increasingly at risk of colliding with uncontrolled
objects. Contrary to the situation with satellites at very low altitude,
there are no effective natural removal mechanisms for objects in
Geostationary Earth Orbit (GEO). Ground-based radars and optical telescopes
belonging to the United States' Space Surveillance Network (SSN) are able
routinely to detect objects larger than 1 m across in GEO. ESA has recently
upgraded a telescope at the Teide Observatory in Tenerife (E) with an
optimised debris-detection system. Its early observations show a hitherto
unknown but significant population of uncatalogued objects with diameters as
small as 10 cm in the geostationary ring. Objects smaller than 10 cm are
also expected to exist, but these are unobservable even with the 1 m Teide
telescope. Further observations are urgently needed to determine the extent
and origin of this debris population, and the resulting hazard to
operational spacecraft.

Flury W, ESOC, ESA Directorate Tech & Operat Support, Mission Anal Sect,
Darmstadt, Germany.
ESOC, ESA Directorate Tech & Operat Support, Mission Anal Sect, Darmstadt,
Astron Inst, Bern, Switzerland.
ASRO, Turku, Finland.
European Space Agcy, Estec, Div Mech Syst, Directorate Tech & Operat
Support, NL-2200 AG Noordwijk, Netherlands.

Copyright © 2001 Institute for Scientific Information


From the Statistical Assessment Service, 1 January 2001

The Top Ten Silliest, Most Misleading Stories of the New Millennium
(at least, we think it's ten, and we're pretty sure that the Millennium has
already started)

Yes, science fans, it's that time of year again, when STATS -- the
Statistical Assessment Service -- looks back with amusement at the glitches
and goofs served up by the media over the last twelve months. It was a
banner year for dubiousity, ranging from failed presidential pop quizzes
(Vajpayee, Lee, and um, that general from Pakistan -- we knew that) to the
amazing electoral counting catastrophe (we thought those were boxes of
Florida grapefruit; turns out that's just what happens to a pregnant chad).
So, return with us now to those thrilling stories from yesteryear...

1). "Well, OK, maybe it's the SECOND time in 50 million years..."
The August 19 New York Times front page was a real scorcher - complete with
color photograph. "The North Pole is melting" read the first sentence. It
seems tourists on a Russian ice-breaker saw open water in the middle of the
polar ice, clicked the shutter, and rushed right to The Times with "evidence
that global warming may be real and already affecting climate." It was a
sight "presumably never before seen by humans... the last time the pole was
awash in water was more than 50 million years ago." National Public Radio
also heralded the news (Aug. 22), but their science reporter, Richard
Harris, started to notice the story's own thin ice, and got a skeptical
response from other Arctic experts. It turns out during a typical summer,
about 90 percent of the high Arctic is covered with ice, but about 10
percent of the time there's open water over the pole. The Times started
backtracking, and on August 29 revisited the entire matter with a Science
Times article altering the claim and its link to global warming.

2). Perhaps you should stick to the swimsuit competition?
Could nuclear power plants be a cause of infant mortality? This charge was
leveled in Washington, DC (Reuters Apr. 27) by activist groups coupled with
the star power of supermodel Christie Brinkley. Though infant mortality
rates have been in sharp decline at the same time that nuclear power spread
around the country, the activists had an angle -- improvements in infant
health were linked to the closing of nuclear plants. But a quick call to the
National Cancer Institute (NCI) by Newsday reporter Earl Lane pulled the
plug. An NCI study that examined 900,000 cancer deaths in counties near
nuclear facilities showed that childhood deaths from diseases such as
leukemia were actually higher before, not after, their construction. If
anything, the facilities were associated with better infant health.

3). Migrating Monarchs Take Wrong Turn?
What was the notorious Butterfly Ballot doing in wintry Canada, so far from
its Palm Beach electoral home? The December 7 issue of Nature presented
research from a Canadian psychologist who offered ballot choices to shoppers
at the Bonnie Doon Mall in Edmonton, Alberta. It seems that 3 out of 53
Canadian shoppers made the alleged "Buchanan error"on the ballot form; that
is, they got confused and voted for the wrong candidate. The San Francisco
Chronicle (Dec. 1) and other papers were quick to net the story, reporting
evidence of "systematic confusion" and arguing the data "call into question
the validity of the presidential election results." A story with, er, wings,
or just a lepidopteran let down?

It turns out the methodology was meandering. The shoppers were only a
"convenience sample" not even representative of Canadians, much less
Floridians. Second, the study acknowledged that "there was no relation
between the amount of confusion and errors" made (so much for "systematic").
Besides, the Associated Press (Nov. 10) had already reported butterfly
ballot "research" from Bossier City, Louisiana. Down there two fourth grade
teachers had tested 22 kids on the same confusing format, with zero errors.

4). "So, have you stopped beating your wife yet?"
Reuters reported a poll (Feb. 4) which illustrated that "although most
smokers in the US know that cigarettes can cause heart and lung disease, few
have been able to kick the habit." In fact, out of the 70 percent of the
sampled respondents who had ever tried to quit, none had succeeded.
Unfortunately, this should have come as little surprise, since the poll
specifically sampled "more than 1,000 adult smokers." No quitters allowed.

5). The View From... Lake Rudolf?
It''s not exactly "Eurocentric," but there's definitely something wrong
here. According to the BBC (Oct. 30), research into the last universal
common ancestor of human males living today "gives an intriguing insight
into the journey of our ancestors across the planet, from eastern Africa
into the Middle East, then to southeast and southern Asia, then New Guinea
and Australia, and finally to Europe and Central Asia" (emphasis added)

It seems that modern man hasn't yet reached North or South America. Perhaps
the controversy over Kennewick Man goes deeper than we think.

6). Kindergarten Cop-out
An Associated Press story, "Federal study shows kindergarten improves all
young minds" (Dec. 4), seemed to suggest that kindergarten was a very good
thing. From a sample of 22,000 children who attended kindergarten, the study
found that five times as many of them could do simple sums as in the
previous year.

But the fifth paragraph of the story reveals how the study doesn't really
prove anything about children's education in general: "The Education
Department-funded study offers no comparison with children who do not attend
kindergarten." In other words, we don't know whether kindergarten-educated
children are better off than other children. All the study showed was that
kindergarten helps educate children who are in kindergarten. But "all young
minds?" - we just don't know.

7). Fuzzy Math
Nobody at the AP raised an eyebrow when its Oct. 28 story, "Clinton signs
law to combat violence against women," repeated the President's claim,
"'Every 12 seconds, another woman is beaten,' he said. 'That's nearly
900,000 victims every year.'"

Errr, no. One incident every twelve seconds translates to over two and one
half million incidents a year. Or, looked at the other way, 900,000
incidents a year is one every 35 seconds. Either way, those two figures
don't add up.

8). Cashew, Cashew, We All Fall Down
New York Times columnist Paul Krugman found another way to criticize
anti-globalization protestors in his April 19 column, "A Real Nut Case." He
claimed that the World Bank's intervention in Mozambique's cashew industry
benefitted the country's poor farmers, who had suffered compared with the
nation's 10,000 nut processing workers.

Unfortunately for Mr. Krugman, and for Mozambique as well, investigations
later in the year by the Washington Post ("A Less Than Helpful Hand; World
Bank, IMF Blamed for Fall of Mozambican Cashew Industry," Oct. 18) and
Knight Ridder ("World Bank Policies Had Mixed Results in Mozambique," Sep.
17) found that the World Bank's policies had not only put over 7,500 factory
workers out of a job in one of the world's poorest countries, but that the
farmers who were supposed to have benefitted had lost out to nut
speculators, many of them foreign.
(Thanks to for initially drawing our attention to this one).

9). Ancestral Vices
A sense of perspective is important when you deal with statistics. A
spokesman for the White House Office of Drug Control Policy clearly lost his
when he responded to a study on the number of drug offenders in prison by
saying, "Over the same period of time, drug use has gone down and crime is
at an all-time low." ("Drug Offenders Jailed at High Rate, AP, Jul. 27)

While crime has gone down recently, it still has not reached the low levels
it began to leave behind in the late Sixties. Murder rates are lower than in
the gangster-ridden 1920's and 1930's, but far above the levels of the
1950's and the first two decades of the century.

Of course, we don't have the data to talk about crime levels before that,
but perhaps the spokesman had something else in mind. When Cain murdered
Abel, after all, the homicide rate peaked at 25,000 per 100,000 individuals.
And the Garden of Eden suffered a 50 percent larceny rate, which was,
naturally, motivated by a desire for illegal substances.

10). And Finally...
"Hyper-hyperbole. It's massive!"-- article title in the UK newspaper The
Observer, Feb. 27, criticizing news media which make exaggerated claims to
bolster their arguments.

"It's apocalypse now as world boils over."-- headline in the same newspaper,
same day.

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