CCNet 59/2001 - 24 April 2001

"No one knows how many impacts took place, or when, or with what
severity, over the past 5 million years. But we know very little about
specific impacts in this time frame, and virtually nothing at all
about their actual environmental effects. [There is] no evidence of
an impact associated with a hominid extinction."
--David Morrison, NASA Ames Research Center, 24 April 2001

"The findings by Peiser and Paine are underpinned by a significant
number of large impact craters. So far, 32 impact craters have been
discovered that are younger than 5 million years. One is 32 miles (52
kilometers) in diameter, three are between 6 and 12 miles (10 and 20
kilometers), one is between 3 and 6 miles (5 and 10 kilometers) and 25 are
less than 3 miles (5 kilometers) in diameter. However, it should be
noted that it takes very unusual conditions to preserve craters of
this size for more than a few hundred thousand years.", 24 April 2001

"But regardless of whether cosmic messengers helped make us who we
are, there is one thing researchers seem to agree on: Given the
evidence that our ancient ancestors were clustered in a relatively
small area (in Africa) you are somewhat lucky to be reading about all this.
"Asteroids certainly had the opportunity to wipe out man at his
roots," said Jack G. Hills, an asteroid specialist at Los Alamos
National Laboratory. "Only good luck prevented it."
--Robert Britt,, 24 April 2001


    SpaceDaily, 24 April 2001

    Ron Baalke <>

    Space.Ref, 23 April 2001

    Rainer Arlt <>

    Chadwick B, Claeys P, Simonson B

    Twitchett RJ, Looy CV, Morante R, Visscher H, Wignall PB

    Morbidelli A, Petit JM, Gladman B, Chambers J

    Duncan Steel <>

     Jon Richfield <>

     Michael Paine <>

     The Guardian, 21 April 2001


From, 24 April 2001

By Robert Roy Britt
Senior Science Writer

In the 5 million years or so that it took for apes to become human, many
human-like branches of the evolutionary tree were lopped off. Scientists
have long wondered why these other hominid species, estimated to number a
dozen or more, didn't make it.

Were those who came to travel to the Moon and ponder their very origin the
logical and inevitable victors in the most important of all Darwinian

Or did we just get lucky?

A newly presented mathematical argument suggests that the birth of Homo
sapiens was guided by catastrophic asteroid or comet impacts, which created
climate conditions that competing species, frankly, couldn't handle.

It also holds that our human ancestors avoided early elimination by the
statistical skin of their rotting teeth.

"The reason that Homo sapiens have survived in spite of these global
disasters has little to do with the traditional explanations given by
neo-Darwinists," said Benny Peiser, a social anthropologist at Liverpool
John Moores University. "It is sobering to realize that we are alive due to
cosmic luck rather than our genetic makeup."

Peiser bases his argument on the fact that populations of hominids and early
modern humans were extremely small. "Had any of these impacts occurred in
the proximity of these population groups, we might also have gone the way of
the dodo," he said.

The study's assumptions and calculations have met with strong caution and
even sharp criticism among scientists who specialize in evolution, as well
as asteroid experts.

Adaptive advantage

David Balding, a professor of applied statistics at University of Reading in
the U.K., said the idea that human survival is due to "cosmic luck" does not

"Perhaps we were lucky in avoiding a massive impact, but perhaps it was our
adaptive advantage that helped us survive modest regional impacts whereas
our hominid cousins did not," said Balding, whose own research focuses on
human evolution.

But some called the new scenario plausible. It has not been published in a
peer-reviewed journal but it is based on impact estimates that are generally
accepted by the asteroid research community, though there are disagreements
over the precise number of times a large asteroid or comet has struck our

Peiser laid the idea out earlier this month at a conference, "Celebrating
Britain's Achievements in Space." He worked with Michael Paine, a volunteer
for the Planetary Society in Australia who ran impact scenarios through a
computer program. (Paine has written freelance stories for in the

The researchers concluded that there would have been 20 "globally
devastating" impacts during the past 5 million years, with effects strong
enough to have had "a catastrophic and detrimental effect" on human
evolution. Five million years ago is roughly the time when hominids diverged
from other apes, though some recent controversial evidence puts the split as
far back as 6 million years ago.

Did space rocks set the human stage?

No one argues that asteroids can be devastating when they tangle with Earth.
An impact 65 million years ago is widely believed to have spurred the demise
of the dinosaurs and many other animals and plants.

But efforts to tie other, more ancient mass extinctions to impacts remain
inconclusive. While extinctions are clearly identifiable in fossil records,
impact evidence seems not to survive the millennia as well. So impact
estimates are based largely on the Moon -- a nearby archive of countless
craters that have not eroded much over time.

Still, because scientists have not witnessed a severe impact, the presumed
effects are speculative.

If an asteroid larger than a kilometer (0.6 miles) hit the planet, it would
cause instant death across a wide area near the site of impact, and
researchers generally agree that drastic climate changes could last a year
or more. Even our protective ozone layer could be damaged, studies have

But the precise consequences of these effects are not known. It is thought
that long-term climate change could make life impossible for many species,
which in turn would cause mass death that might move up entire food chains.

Peiser suggests another possible effect: "The abrupt loss of the ozone layer
and the sudden release of toxins may even affect the DNA in some unknown
manner, thus triggering macro-mutations, including the sudden reorganization
of entire genomes."

Ellen Thomas, a Wesleyan University research professor who examines how
climate change affects evolution, said few evolutionists would by this
argument of quick, significant changes in the genetic blueprints. Instead,
macro-mutations are seen by many as a genetic dead end.

"Macro-mutations can hardly ever lead to evolution," Thomas said. "They lead
to non-viable organisms."

Basic numbers questioned

Of course to affect human evolution in any fashion, a space rock first has
to hit Earth. But "no one knows how many impacts took place, or when, or
with what severity, over the past 5 million years," said David Morrison, an
asteroid expert at NASA's Ames Research Center in California.

Morrison told that instead of the 20 potentially devastating
impacts assumed by the study, he expects there were probably only five or 10
with enough energy to create global environmental effects.

"But we know very little about specific impacts in this time frame, and
virtually nothing at all about their actual environmental effects," Morrison
said, adding that there is "no evidence of an impact associated with a
hominid extinction."

Morrison did not discount the whole idea, however.

"I would be surprised if impacts had not had some influence on early hominid
populations and perhaps evolution," he said. "On the other hand, I am not
convinced that impacts led to numerous extinctions in the past 5 million
years. This is all interesting speculation, but specific data are lacking on
either impacts or extinction events and there is no known correlation
between the two."

Peiser counters that the estimates used in the study are "very
conservative." He acknowledges that shortcomings in the human fossil record
(fossils on land erode more easily than those in the oceans) "are far too
big to allow any direct correlation between impact catastrophes and hominid
extinction." But he said that the study shows that "impact catastrophes that
occurred during the crucial period of human evolution should no longer be

Still, it is clear that more research will be needed before any consensus

"What [Peiser and Paine] may have added," said Balding, the statistics
professor, "is some quantitative simulations to make more precise some well
established speculations."

Speculation about evolution is nothing new. And the more one delves into the
nitty-gritty of our own past, the stronger the criticism gets over Peiser's
attempt to reinvent Darwin.

Does Darwin need reinventing again?

If asteroid experts are sometimes a mile apart on their view of history --
and they are -- then evolutionary theorists live on different continents.

Followers of Charles Darwin have long believed that failed branches of our
ancestry reflect a common mode of evolution, whereby species are gradually
replaced by more advanced species that adapted because of their superior
genetic fitness.

But in recent decades, a different view called punctuated equilibria has
taken hold. This theory, first put forth in the 1970s by Stephen J. Gould
and Niles Eldredge, expects sharp changes in evolution.

In either scenario, luck plays a role. And both fit within the most famous
of Darwinian themes, survival of the fittest. But the rapid shifts assumed
in punctuated equilibria, be they caused by sudden disasters or other means,
are thought to be the mechanism by which one species replaces another.

"There has been debate for over 100 years on whether evolution is gradual or
punctuated," said Balding.

And the debate continues. Recent fossil findings have some researchers
leaning back toward the gradual approach to human evolution.

Peiser said his study supports punctuated equilibria, and helps explain why
"almost all hominids, i.e. the 14 known species of human ancestors, have
become extinct during the last 5 million years."

But Wesleyan's Ellen Thomas said it is not even known that there were 14

"The human fossil record is incomplete, and it is not easy to agree on which
fossils belong to different species," Thomas said in an e-mail interview.
"The experts disagree wildly."

Thomas echoed other scientists in pointing out that there is no fossil
evidence -- neither of human remains in Africa nor marine organisms, which
leave a much more complete record -- that reveal any mass die-offs during
the 5 million-year period covered in Peiser's study.

"And if the extinctions affected humans, they should show up in the
extinction record of other organisms as well," Thomas said. "The paper just
shows that many impacts, many of which could have been damaging, possibly

But Peiser argues that no expert on near-Earth asteroids, the space rocks
known to exist in our region of the solar system, questions that "many such
global disasters must have occurred." Yet he said "all textbooks on human
evolution completely ignore the occurrence of catastrophic impacts."

Other forces of evolution

While Peiser and Paine suggest that comets or asteroids are a driving force
behind evolutionary change, it is the climatic consequences of impacts that
are the would-be crushing mechanisms for fledgling species. Other
researchers have long debated possible links between climate change and
human evolution.

For example, cold periods are suspected of forcing migrations that created
small, isolated groups that could have evolved significantly but then died
out. One such period may have occurred as recently as 71,000 years ago. But
firm links between climate and serious evolutionary changes elude

One recent international study, released earlier this year and led by Jeremy
Marlow of Newcastle University, showed evidence of a significant cooling of
the climate 2 million years ago that the authors said "adds weight to the
theory that climate change played a significant part in the evolution of
early humans."

Further clouding the possibilities, recent findings have hinted at the
possibility that the worst extinctions might require multiple killing
mechanisms, such as when an impact, or perhaps several, happens to occur
during a time of heavy volcanic activity.

Irony in our existence

In an ironic preface to the whole argument, it's possible that asteroids and
comets were responsible for life in the first place. A growing movement
among astrobiologists suggests that rocks from space brought critical
building blocks that stimulated the initial biological activity in the
earliest primordial soup billions of years ago.

But regardless of whether cosmic messengers helped make us who we are, there
is one thing researchers seem to agree on: Given the evidence that our
ancient ancestors were clustered in a relatively small area (in Africa) you
are somewhat lucky to be reading about all this.

"Asteroids certainly had the opportunity to wipe out man at his roots," said
Jack G. Hills, an asteroid specialist at Los Alamos National Laboratory.
"Only good luck prevented it."


The following details of the new idea were provided by Benny Peiser and
Michael Paine and appear here with only minimal editing for style and

The findings are calculated on the basis of the generally accepted "impact
rate" (i.e. the rate of cosmic impacts calculated from terrestrial and lunar
impact craters together with the currently observable flux of asteroids and
comets in the solar system). A computer simulation of cosmic impacts over a
5 million-year period was chosen to give an indication of the environmental
disruptions that have occurred during the evolution of our species.

These consequences can be categorized into:

A. Local -- devastation over a radius of tens of (miles) kilometers. No
serious regional or global consequences

B. Moderate regional -- devastation over a radius of hundreds of miles
(kilometers) -- the size of a small country. Short-term regional climatic

C. Severe regional -- devastation over 600 miles (1,000 kilometers) (the
size of a large country). Severe regional climatic disruption. Mild,
short-term global climatic disruption -- year without summer.

D. Moderate global -- devastation over thousands of miles (kilometers) --
continental. Severe global climate disruption lasting several years. Global
food chain failures

E. Severe global -- global firestorms from ballistic entry of impact debris.
Extreme worldwide climate disruption for decades to centuries. Extinctions.

For everything except the last category, the effects on early human
populations depend on proximity to the impact -- a matter of luck. In
addition to climate disruption (mainly darkness and cooling), the larger
impacts could lead to global warming due to the greenhouse effect (water and
carbon dioxide), loss of the ozone layer (particularly with ocean impacts
that propel chlorine into the upper atmosphere), acid rain and toxins.

The simulation looked at the worst event in each of 5,000 millennia. It
therefore gives an underestimate of the total number of impacts.

The program recognizes five outcomes of an asteroid or comet colliding with

The object skims the atmosphere and flies harmlessly back into space. This
happened in 2 percent of the millennia.

The object explodes above land in an airburst similar to an atomic
explosion. This happened in 17 percent of the millennia.

The object impacts the land and forms a crater. This happened in 11 percent
of the millennia.

The object explodes in an airburst above an ocean. This was the most
frequent outcome, accounting for 41 percent of millennia. Fortunately, until
recently, most of these impacts would have been harmless to land dwelling

The object impacts the ocean, forming tsunami and, possibly, ejecting vast
quantities of water and salt into the atmosphere. This happened in 28
percent of the millennia. (Larger impacts may also reach the ocean floor and
cause similar effects to a land impact)

Over the period of the simulation some 57 percent of millennia suffered an
impact that would potentially have consequences for land-dwelling creatures.
In most cases they would only be affected when they were close to the impact
site. The situation is different now with significant human populations
living in low-lying coastal areas.

Size impactor (The letters refer to the typical environmental consequences.)

1,650 to 2,950 feet (500 to 900 meters) (C): 108 events
0.6 to 0.9 miles (1 to 1.5 kilometers) (C/D): 24 events
1 mile (1.6 kilometers +) (D/E): 13 events

Craters (The letters refer to the typical environmental consequences.)
Over the 5,000 millennia a total of 552 craters were formed on land. Of

477 were less than 3 miles (5 kilometers) in diameter (A);
64 were between 3 and 6 miles (5 and 10 kilometers) in diameter (B);
nine were between 6 and 12 miles (10 and 20 kilometers) in diameter (C);
two were more than 12 miles (20 kilometers) (D).

There were also six ocean impacts that could be expected to produce
moderate-to-severe global climate disruption (D/E), particularly destruction
of the ozone layer. Three of these involved transient craters more than 31
miles (50 kilometers) in diameter and would probably have penetrated to the
ocean floor.

Therefore, during this simulation severe climate disruption occurred, on
average, every million years (i.e., two land impacts and three ocean

The findings by Peiser and Paine are underpinned by a significant number of
large impact craters. So far, 32 impact craters have been discovered that
are younger than 5 million years. One is 32 miles (52 kilometers) in
diameter, three are between 6 and 12 miles (10 and 20 kilometers), one is
between 3 and 6 miles (5 and 10 kilometers) and 25 are less than 3 miles (5
kilometers) in diameter. However, it should be noted that it takes very
unusual conditions to preserve craters of this size for more than a few
hundred thousand years.


Copyright 2001,


From SpaceDaily, 24 April 2001


From Ron Baalke <>

From The Courier Mail, 20 April 2001,5936,1912401%255E3102,00.html

Boom shakes, but fails to stir quake sensor
Staff reporters

THOUSANDS thought it was an earthquake, others thought it was a bomb.
Buildings shook, windows rattled, dogs howled.

There were no report of damage, but a mystery boom that rocked a 142km
stretch of the coast in south-east Queensland left lots of worried residents
in its wake.

Earthquake sensors did not register a disturbance, even though the 15-second
"boom" hit thousands of homes between Buderim and North Stradbroke Island.

Earthquake monitoring centres were flooded with calls that a tremor had hit
just after 3.30pm, but no damage was reported.

Last night the RAAF admitted that one of its F-111s had gone supersonic east
of Ballina in NSW. But they played down the chances that the jet was cause
of the boom.

RAAF Wing Commander Rob Lawson said the F-111, flying at 160m, finished its
manoeuvre 100km off the coast at Beenleigh.

He said he could not rule out the possibility that the jet had caused the
"tremor". But "we go supersonic there all the time and people in Brisbane
don't ever notice it," he said.

Air traffic control agency Airservices Australia said last night there was
an area of air space off the coast where military aircraft were permitted to
fly faster than sound.

Spokesman Richard Dudley said while that area did not extend as far north as
Bribie Island, it was possible given certain weather and wind conditions
that the sound of a sonic boom might travel some distance.

"However, that would not explain vibrations people reported experiencing,"
Mr Dudley said.

Relieving Moreton Island ranger Scott Rogers said he was in his office when
the whole building began to shake.

Stradbroke Island resident Mark Davis said his TV shook and his dogs bolted
when the plane flew over his home yesterday at Point Lookout yesterday.

"The dogs were sitting on the loungeroom floor and they freaked, jumped up
and took off out the door," Mr Davis said.

Bongaree resident Darren Jellick said he felt an "enormous shudder and heard
a loud bang" while working at Bribie Island. "It was the sort of sound you
hear when a military bomb blows up," he said.

Bribie Island's Rod Bennett was shaken from sleep.

"I was sure someone was trying to break into the house. It was a really
violent shaking of the windows, I thought they were going to break," Mr
Bennett said.

Copyright 2001, The Courier Mail


From Space.Ref, 23 April 2001

Photos of Two Minor Debris Impacts Leonardo MPLM Suffered on its Inaugural

By Keith Cowing

These pictures were taken of the Leonardo MPLM (Multi-Purpose Logistics
Module) at NASA KSC after it returned to Earth from its first mission.
Leonardo is one of three MPLM's provided by Italy and was flown to the
International Space Station last month on mission STS-102/ISS-5A.1.

These photos show micrometeoroid damage to a micrometeoroid/orbital debris
(MMOD) shield panel from MPLM FM1 (Leonardo). The panel was penetrated in
two spots (the small pinholes in the photos), but did not damage the
multi-layer insulating blanket beneath. This module was in space for about a

The strike damage to Leonardo's MDPS (micrometeorite protection system) is
characteristic of other impacts that have been seen on spacecraft. However,
the size of particle that penetrated the shield was a bit larger than
average and was estimated to be traveling rather fast - at least 10
kilometers/second - when it struck Leonardo.

To put this impact into perspective, had this piece of space debris hit a
Space Shuttle window it would have left a crater approximately 1 inch (2.5
cm) in diameter. If it had hit a someone wearing an EVA spacesuit it would
have gone partially through the suit and left a bruise on the person wearing
the suit.

Impacts such as these two are routine for any spacecraft in Earth orbit. The
Long Duration Exposure Facility (LDEF) which spent 5.7 years in Earth orbit
had been struck more than 20,000 times by the time its was brought back to
Earth. The Hubble Space Telescope had nearly 800 impacts by the time it was
repaired in 1997.

How much debris a spacecraft can expect to collide with - the orbital debris
flux - is a function of mission duration, the size and orientation of the
spacecraft (how big of a target it is), the orbital inclination, altitude,
and the level of solar activity.

Components of the International Space Station are provided with shielding so
as to reduce the annual risk that impact with a space debris could cause a
critical failure to less than 0.5% This shielding is also sized to last
through the expected 15 year operational lifetime of the ISS.

Last year, it was discovered that the Service Module did not have sufficient
shielding to meet requirements levied upon it by the ISS program. As such,
additional shielding panels will be delivered and installed on the exterior
of the Service Module.

Copyright 2001 SpaceRef Interactive Inc. All rights reserved.


From Rainer Arlt <>


            I M O   S h o w e r   C i r c u l a r


                          LYRIDS 2001

Very favourable lunar conditions made this shower a highlight target of
2001. Occasionally heightened activity is observed from the Lyrids, most
notably in 1982. The 2001 maximum exhibited a slightly enhanced level of
activity. Observations from 49 observers were collected by April 24, 0h UT.
Such a large number of observations monitoring a shower of moderate activity
is a fairly nice success of amateur meteor observing. The table of the
activity graph is given below.

The maximum is broad; highest rates are found near a solar longitude of
lambda = 32.0 deg with ZHR = 33+-3. The first peak at lambda = 31.7
comprises a number of novice observers
who may have underestimated their limiting magnitudes. Nevertheless, the
up-and-down or -- more roughly speaking -- the general plateau shape of the
activity profile appears to be a typical feature of the 2001 Lyrids. This
was already found in recent Lyrid activity profile. This year, the plateau
may extend over as much as 24 hours. ZHRs in 2000 were lower, 20 at best, in
1999 near 30 as this year, but again significantly lower in 1998 with values
below 20.

2001   Time    Sollong     nObs  nIND   nLYR     ZHR
Apr    (UT)    (J2000)
17     0620     27.295       2     1      0      3  +-3
19     0600     29.237       1     1      0      7  +-7
20     0130     30.030       1     1      3      3  +-2
20     2200     30.864       6     2     13      5  +-1
21     0140     31.013       8     5     30      8  +-1
21     1800     31.678       8     7     85     37  +-4
21     2130     31.820      18    13    155     28  +-2
21     2320     31.894      13    13     67     18  +-2
22     0000     31.922      10    10    128     28  +-2
22     0100     31.962      14    12    117     19  +-2
22     0230     32.023      10    10     90     33  +-3
22     0900     32.287       8     5     54     27  +-4
22     2130     32.795       3     2     19     24  +-5  
23     2200     33.791       2     2      7      8  +-3

We are very grateful to the following observers for their efforts and quick
reporting of data:

ANTDU  Dusan Antic (Serbia)          MENHU  Huan Meng (China)
ARLRA  Rainer Arlt (Germany)         MILAA  Ana Milovanovic (Serbia)
BASLU  Luc Bastiens (Belgium)        MISKO  Koen Miskotte (Netherlands)
BETFE  Felix Bettonvil (Netherlands) MODAM  Amruta Modani (India)
BHANE  Neha Bhandari (India)         NISMA  Markku Nissinen (Finland)
BHASU  Sushrut Bhanushali (India)    PATSO  Sonali Patil (India)
DECGO  Goedele Deconink (Belgium)    PEEBJ  Bjorn Peeters (Belgium)
DEOPA  Parag Deotare (India)         PRAMA  Mayuresh Prabhune (India)
DUBAU  Audrius Dubietis (Lithuania)  PUNNI  Nilesh Puntambekar (India)
FANYU  Yuwei Fan (China)             RENJU  Juergen Rendtel (Germany)
GADSH  Shirish Gadkar (India)        SAVBR  Branislav Savic (Serbia)
GEOPE  Petros Georgopoulos (Greece)  SONWA  Wanfang Son (China)
GEYBE  Benny Geys (Belgium)          SUNHU  Huiming Sun (China)
GLIGE  George Gliba (USA)            TRIJO  Josep Trigo-Rodriguez (Spain)
GOLDA  Darja Golikowa (Germany)      TUKAR  Arnold Tukkers (Netherlands)
HASTA  Takema Hashimoto (Japan)      UCHSH  Shigeo Uchiyama (Japan)
JOHCA  Carl Johannink (Netherlands)  VELKR  Kristina Veljkovic (Serbia)
KULMA  Manali Kulkarni (India)       VERJN  Jan Verbert (Belgium)
KULRH  Rhikesh Kulkarni (India)      VUJKA  Katarina Vujic (Serbia)
KULVI  Vineet Kulkarni (India)       VUJRO  Romana Vujasinovic (Serbia)
LANMA  Marco Langbroek (Netherlands) WANSH  Shuo Wang (China)
LINMI  Mike Linnolt (USA)            WISJE  Jean-Marc Wislez (Belgium)
LUNRO  Robert Lunsford (USA)         ZERZO  Zorana Zeravcic (Serbia)
MARAN  Antonio Martinez (Venezuela)  ZHUJI  Jin Zhu (China)
MCBAL  Alastair McBeath (UK)         ZUPLJ  Ljubica Zupunski (Serbia)

Solar longitudes refer to equinox J2000.0. nObs is the number of individual
observing periods, nIND is the number of individual observers providing
them, nLYR is the number of Lyrids seen. The radiant position was assumed at
alpha=271, delta=+34, the population index used was r=2.9. The expectation
value of the ZHR,

         ZHR = (1 + sum nLYR) / sum(Teff/C),

was used for the averages here, where Teff is the effective observing time
and C is the total
correction composed of limiting magnitude, clouds, and zenith correction.
Times are rounded to
the nearest 10 minutes.

Rainer Arlt & Vladimir Krumov,
2001 April 24



Chadwick B, Claeys P, Simonson B: New evidence for a large Palaeoproterozoic
impact: spherules in a dolomite layer in the Ketilidian orogen, South

An unconformable sedimentary succession deposited between c. 2130-1848 Ma on
Archaean gneisses of the foreland of the Palaeoproterozoic Ketilidian orogen
includes a layer with coarse sand-sized silicate spherules. The layer is c.
1 m thick and consists mainly of coarse diagenetic dolomite. In addition to
c. 18% spherules, the layer also contains 3% well-sorted, very fine
quartzose sand and 6% larger intraclasts of chert and carbonate. The
spherules were previously interpreted as microfossils (Vallenia sp.) because
of their spheroidal shapes and inclusions of carbonaceous matter. The
spherules are reinterpreted as replaced impact ejecta because they have
shapes typical of splash-form microtektites, some contain possible examples
of replaced skeletal spinel crystals, perlitic cracks and devitrification
spherulites, and non-spherical particles with shapes and textures of typical
glassy and scoriaceous volcanic ash are absent. The carbonaceous matter is
attributed to hydrocarbons that migrated into the spherule layer from
elsewhere in the sedimentary succession. The spherules were reworked after
deposition, probably as a result of turbidity currents or storm- or
impact-induced waves. Analysis of one spherule-bearing sample revealed only
0.02 ppb iridium, a value comparable with low iridium abundances in distal
layers of other terrestrial impact ejecta. The spherules in South Greenland
are the first distal impact ejecta recognized in mid-Precambrian strata.
They represent a major impact because their aggregate thickness exceeds the
thickest spherule accumulations reported from the Cretaceous-Tertiary
boundary layer. Given their loosely constrained age and the implied scale of
the impact, the Ketilidian spherules could be distal ejecta from either the
Vredefort, South Africa, (c. 2025 Ma) or Sudbury, Canada, (c. 1850 Ma)

Chadwick B, Univ Exeter, Room 220,Laver Bldg, Exeter EX4 4QE, Devon, England
Univ Exeter, Exeter EX4 4QE, Devon, England
Museum Naturkunde, Inst Mineral, D-10099 Berlin, Germany
Oberlin Coll, Dept Geol, Oberlin, OH 44074 USA

Copyright 2001 Institute for Scientific Information


Twitchett RJ, Looy CV, Morante R, Visscher H, Wignall PB: Rapid and
synchronous collapse of marine and terrestrial ecosystems during the
end-Permian biotic crisis
GEOLOGY 29 (4): 351-354 APR 2001

A newly studied Permian-Triassic (P-Tr) boundary section in Jameson Land,
East Greenland, contains an abundant and well-preserved marine fauna as well
as terrestrial palynomorphs. For the first time it is possible to compare
the biotic crises of the marine and terrestrial realms using the same
samples from the same section. The sediments record a negative excursion in
delta C-13(carb) values of 8 parts per thousand -9 parts per thousand, and
in delta C-13(org) values of 10 parts per thousand -11 parts per thousand.
The presence of the conodont Hindeodus parvus, combined with the delta
C-13(carb) record, enables correlation with the proposed global stratotype
section at Meishan. This shows that the Greenland section is the most
expanded P-Tr section known. Collapse of the marine and terrestrial
ecosystems took between 10 and 60 k.y. It took a further few hundred
thousand years for the final disappearance of Permian floral elements.
Collapse of the terrestrial and marine ecosystems began at the same
stratigraphic level and preceded the sharp negative excursion in the delta
C-13 record.

Twitchett RJ, Univ So Calif, Dept Earth Sci, Los Angeles, CA 90089 USA
Univ So Calif, Dept Earth Sci, Los Angeles, CA 90089 USA
Univ Utrecht, Palaeobot & Palynol Lab, NL-3584 CD Utrecht, Netherlands
CSIRO, Inst Minerals Energy & Construct, N Ryde, NSW 2113, Australia
Univ Leeds, Sch Earth Sci, Leeds LS2 9JT, W Yorkshire, England

Copyright 2001 Institute for Scientific Information


Morbidelli A, Petit JM, Gladman B, Chambers J: A plausible cause of the late
heavy bombardment

We show that at the end of the main accretional period of the terrestrial
planets, a few percent of the initial planetesimal population in the 1-2 AU
zone is left on highly-inclined orbits in the inner solar system. The final
depletion of this leftover population would cause an extended bombardment of
all of the terrestrial planets, slowly decaying with a timescale on the
order of 60 Ma. Because of the large impact velocities dictated by the high
inclinations, these projectiles would produce craters much larger than those
formed by asteroids of equal size on typical current near-Earth asteroid
orbits: on the Moon, basins could have been formed by bodies as small as 20
km in diameter, and 10 km craters could be produced by 400 m impacters. To
account for the observed lunar crater record, the initial population of
highly-inclined leftovers would need to be a few times that presently in the
main asteroid belt, at all sizes, in agreement with the simulations of the
primordial sculpting of both these populations. Ifa terminal lunar cataclysm
(a spike in the crater record similar to3.9 Ga ago) really occurred on the
Moon, it was not caused by the highly-inclined leftover population, because
of the monotonic decay of the latter.

Morbidelli A, Observ Cote Azur, BP 4229, F-06304 Nice, France
Observ Cote Azur, F-06304 Nice, France
NASA, Ames Res Ctr, Moffett Field, CA 94035 USA

Copyright 2001 Institute for Scientific Information



From Duncan Steel <>

Dear Benny,

You have today (April 23rd) carried various comments from Ed Grondine in
which he has misrepresented my viewpoints as expressed in my message in
CCNet of April 19th.

>If I interpret Duncan's comments on the Siding Spring Observatory correctly

Grondine did not (interpret my comments correctly). I simply pointed out
that the UK already has an operational telescope that might be equipped in
precisely the same way as its twin at Palomar, the latter having now been
adapted for NEO searching by the NEAT team and colleagues (and good for
them). The telescope in question (the UKST) happens to be an instrument
which many UK astronomers would like to see relinquished so as to free up
some of the funds required for other astronomical research activities. It
would represent an invaluable complement to the Oschin Schmidt at Palomar if
equipped and operated in the same way for NEO searching.

Note that I made no comment at all about "Siding Spring Observatory", which
is an observatory operated as part of the Australian National University. It
simply happens to be the location of the UKST, which is operated as part of
the Anglo-Australian Observatory. By confusing my comments here, as
elsewhere, Grondine muddies the waters.

>it appears that he has accepted that the UK 3.5 meter telescope will not be
>built by a government facing very large bills ...

That is not the case at all and it takes some weird jump in imagination to
derive such a false belief. It is akin to suggesting that because  a bicycle
becomes available for me to pedal to work then it follows that I will give
up saving to buy a new car.

Similarly Grondine's analysis of my comments on the Associated Press report
is entirely incorrect. The AP report was misleading because it made it
appear that the "NASA Spaceguard goal" is 90 percent of all 1 km plus NEOs
(i.e., including Earth-crossing comets), whereas the goal is recognised by
all those with close familiarity with the subject to involve only the NEAs.
And at that, only the NEAs with short-period orbits (because it is beyond us
to discover those 1 km asteroids with perihelion distances less that 1 AU
but aphelia beyond Neptune until such time as they enter the inner solar
system; ipso facto such long-period asteroids are not part of the population
of which 90 percent is the aim).

I made no expression of any personal belief as to whether that specific NASA
goal is adequate in the long term: I simply pointed out why comets and
long-period asteroids are not included in the goal. Indeed, as I am neither
a US citizen nor a US taxpayer, it is not my business to express any opinion
about what NASA should be doing. Perhaps Grondine thinks he has the right to
tell his next-door neighbour whether he (the neighbour) should buy a new car
or not. I do not presume any such right for myself. What I would say is
that, as a person who is not directly involved, I think the US search teams
are doing a wonderful job, and I am happy to lend them my verbal and moral
support. I can write books and magazine articles, I can appear on US radio
and TV, but I have no Congressman to lobby or threaten with losing my vote.
Elsewhere I am pleased to see some NEO activity, such as in Japan with the
new search and tracking activity, and similarly in Italy where apart from
NEO observations there is brilliant dynamical work under way. But it is not
my position to tell the Japanese or Italian astronomers or governments what
they should be doing. Nor is it my place to criticize the NASA Spaceguard
goal, especially since it is NASA-funded projects that are delivering most
of the NEA discoveries. On that basis, congratulations to the US public for
their support of this endeavour. You are leading the way. But in the same
way as one might admire the football or baseball team that is currently
leading the rankings, some of us have ambitions to overtake your efforts.

As regards what I do think myself, as a citizen of the UK, and a UK
taypayer, I permit myself to lobby the UK government in various ways. That
is one of the contributing reasons why the UK NEO Task Force report made
recommendations for the size limit of NEA discoveries to be set somewhat
lower than the NASA Spaceguard goal (and that necessitates larger search
telescopes), and also for scientific studies of the nature of the NEO hazard
(because a group of us in the UK regard giant comets undergoing
disintegrations as being a larger danger to the terrestrial environment than
is perhaps realised by researchers elsewhere).


>Besides giving in to NASA's rather arbitrary goal for asteroids, Steel

I do no such thing, and I would thank Grondine not to make such baseless
statements. What NASA chooses to do is not my business, as I have written.
Similarly, what I choose to do is not NASA's business, and in the UK we have
a different target. In the future I hope that the UK and the USA and many
other nations will be able to work together, but I would expect that at all
times there will be differing opinions about what the priorities should be.
Such working together often takes the form of friendly competition, and if
higher goals are set elsewhere then this might have an influence upon the
goals set in the US. But, again, it is not my place to criticise what any
other nation might be doing.

I further wrote (rather clearly, I believe):

>So far as I am aware the majority of very large objects on
>Earth-crossing orbits observed over the history of astronomical research
>have been comets, mostly in near-parabolic orbits. Finding 90 percent of
>those is not feasible, because they spend most of their time near aphelion,
>making it possible to find them only as they enter the planetary region."

To which Grondine stated:

>Carolyn Shoemaker disagrees with him, and is seeking $170,000,000 for a
>telescope for exactly this purpose.

Again, Grondine has made a false statement based upon his own lack of
understanding of what is involved, even though it is quite simple. Spotting
long-period/near parabolic comets as they cross the 3 AU threshold at which
water starts to sublimate, or rather further out where weaker comae are
produced by the more-volatile constituents (methane, ammonia, CO etc.), is
trivial (compared to finding 1 km asteroids at similar distances). Thus it
is straightforward to
find the majority of such comets that enter the inner solar system, but only
as they do so. (There are, however, some long-period comets that are not
easily discoverable well ahead of an impact if only Earth-based search
systems are employed, for example if they cross the 3 AU threshold while
near superior conjunction.)

As I wrote, it is not feasible to find any substantial fraction of the total
numerical population because one cannot spot comets at 10,000 AU no matter
how much you spend on telescopes, and no-one with half an ounce of
intelligence has suggested that you can. As I wrote, there are 100 million
comets per square degree that are not discernable as individual objects.
Spotting the few that enter the inner planetary region each year is easy, in
most cases.

The problem, as I pointed out previously, is that even if such a comet were
spotted when still some distance away from impact (say when it is at the
distance of Saturn), still a timely intercept is not feasible using
presently-available propulsion systems. You give me a system capable of
achieving a delta-vee of 100 km/sec in short order (that is, not an ion
engine that might reach that speed after a three-year gradual acceleration),
and you have it sitting on a launch pad waiting to go, and I could intercept
most such comets. The reality, however, is not that. Grondine and others
interested in looking into this need to start at the beginning, by examining
the sorts of warning times that are feasible for long-period comets (see the
chapter by Marsden and Steel in 'Hazards Due to Comets and Asteroids',
edited by Tom Gehrels, 1994; if we were lucky we might get 250 to 500 days).
Having understood what is involved in terms of the celestial mechanics, next
they could try to invent an interceptor for some characteristic cometary
orbits, using presently-available propulsion systems. Good luck.

In the meantime, those wanting to move the subject forward and decrease the
chance of a major impact taking us unawares will continue to support the
efforts aimed at tackling the simplest part of the hazard, that associated
with asteroid impacts predictable on a long-term basis (decades). All hail
those NEO search programmes that are delivering the goods now, whilst other
talk and wring their hands. Congratulations to the dynamicists who have
developed the techniques making impact predictions and probabilities
calculable. Once the 1 km goal is achieved, then it can be dropped to half a
kilometre, and then smaller still. The UK NEO Task Force report indicates
what some of us think our own nation should be aiming for in the short term
(the next decade or so). Maybe others will follow suit. In the same way as
we (humankind) have eradicated smallpox, so we can eradicate the danger
posed by large short-period asteroids. Next we'll move on to polio, rubella
and measles, or your disease of choice. The fact that we cannot at present
cure cancer or even the common cold is irrelevant, because by wiping out
some diseases we do enhance the individual's chance of long-term survival.
Similarly it is irrelevant that we cannot hope to tackle the long-period
comets in the near-term, although we'll keep it in mind. When there are
limited resources available they should be directed to where they can do
most good. In our own countries, and the larger organisations of which they
are a part (like the European Community, or the United Nations), we strive
to enhance the resources allocated to the NEO impact hazard. As I indicated
previously, there will come a time when the asteroid problem is solved, and
then long-period comets take over, just as at present there is very little
spent on tackling smallpox. By then maybe we will have the propulsion system
necessary, and everything else required.

Getting the NEO impact hazard accepted by the general public and by
politicians, and then getting the appropriate actions taken to ameliorate
the danger, require clear and distinct signals to be given. The Associated
Press story added to the signal, but also enhanced the noise/confusion level
slightly because in certain aspects it was incorrect. Grondine's message
contained a number of false statements and incorrect deductions which
amplify the noise without adding any significant signal.

Duncan Steel


From Jon Richfield <>

Hi Benny,

In response to the remarks of Robin Lloyd:

>Birthright aside, can a planet-sized object that fails to orbit a
star still be called a planet? The standards-setting International
Astronomical Union (IAU) recently issued a provisional answer -- no
way. Planets, by their new definition, must orbit a star. That definition
could be revised as more data come in and the group continues to meet.<

I can well believe that to call the committee discussions "contentious" was
putting it mildly.  This is about standard for invention of terminology. One
of the main problems is that such committees seldom start with a clear
listing of the entities to be named and a basis for
the nomenclature. Perhaps I wrong them, but the outcome seems about par for
the course. Given the complexity of the situation, one could simply coin ad
hoc terms as the need arises: how about "Kuiperoids" and "Oortoids" for a

I am uncomfortable with the limitation of the use of the word "planet" in
particular, because it means "wanderer", which seems very suitable to a wide
range of objects, but I suppose that that particular baptism is now beyond
redemption.  "Brown sub-dwarfs" is getting off lightly on balance...
Abortasters or fetasters seems to me to better, but would you believe, they
never asked me! Then for wandering non-brown-sub-dwarfs how about exoplanets
or simply free planets?

This is just a reaction to a lot of about-it-and-abouting that seems to be
starting to spill right out of the teacup.  Bad terminology can be a real
nuisnace in the long term, as well as grating on the sensitive ear.  Why not
get someone in forum to present a nice, complete list of the classes of
object under consideration with clear distinctions between them, and ask for
serious suggestions for a useful terminology? In fact, if the dimensions of
distinction are clear enough, I could even suggest schemes for automatically
generating names for each class.




From Michael Paine <>

Dear Benny,

I find NASA's budget priorities a little strange. If this report is to be
believed then during the next decade $1 billion will be spent on a telescope
to "to study and potentially discover planets orbiting distant stars". While
I support the search for extra-solar planets and potential abodes for other
forms of life it would be nice to see just a fraction of this money go
towards ensuring that the only life we know of is not wiped out by a large
asteroid or comet.

Michael Paine

Princeton U. scientists design telescope for NASA competition

By Vanessa Woods
The Daily Princetonian
Princeton U.

(U-WIRE) PRINCETON, N.J. -- It is possible that human beings are only a
decade away from finding out whether or not it is alone in the Universe, and
Princeton University is playing a large role in this potential discovery.

A group of six University faculty members, three graduate students and a
postdoctoral fellow has teamed up with scientists from the Space Telescope
Science Institute in Baltimore, Md. and Ball Aerospace in Boulder, Colo. to
form one of four teams in a NASA-run competition.

To participate in the competition, all four groups are required to design
and create a $1 billion telescope to study and potentially discover planets
orbiting distant stars. The NASA mission is scheduled to begin the launching
of the winning telescope as early as 2012.

Assistant professor of mechanical and aerospace engineering Jeremy Kasdin is
leading the University's team, which has made several advances in its work
since they began working last summer. Kasdin said he became involved in the
project a year and a half ago, just a few months after coming to Princeton.

Kasdin explained that the main purpose of NASA's mission is to gather as
much information as possible to find the best way to find an earth-like
planet and "to gather information on whether or not it could potentially
harbor life."

Kasdin also participated in a NASA space project at Stanford University and
discovered his current project on NASA's website.

"NASA made it very clear that it wanted industry teamed up with academia in
this mission," he said.

Princeton is not the only university bringing academia to the partnership.
The other universities involved include the University of Arizona, the
University of Colorado and the Massachusetts Institute of Technology,
according to Kasdin.

However, the University has made some very significant steps toward
completing NASA's mission. The major breakthrough of Princeton's team is "a
very unique telescope design that nobody has done before," said Kasdin.

Nicknamed "The Pupil," the telescope was designed by University astrophysics
professor David Spergel. Spergel was unavailable for comment.

Also on the University's team are mechanical and aerospace engineering
professor Michael Littman and astrophysics professor Edwin Turner who is in
Tokyo. Both were unavailable for comment.

Though Kasdin noted the team members might not all share the same view as to
the possibility of other earth-like planets with life forms, he said he
believes earthlings may find they actually have extraterrestrial neighbors.

"I lean towards the side of people who believe there is a very high
likelihood of the [existence of earthlike planets] out there," he said.

He also noted that some scientists believe it is nearly impossible for
another planet to have the same life-promoting qualities that Earth has. 

Kasdin also explained that no one has actually seen an earth-like planet
through a telescope so it is difficult for any scientist to predict the
possibility of alternate life forms. "No one has any idea what to expect,"
he said.

Nevertheless, the University's team is certainly trying to make a great
contribution to science regardless of whether or not an earth-like planet
with extraterrestrial life is found.

"There's going to be a lot of different kinds of science done with this,"
Kasdin said.

(C) 2001 The Daily Princetonian via U-WIRE


From The Guardian, 21 April 2001,3604,476191,00.html

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