CCNet 15/2002 - 25 January 2002

"This point is important to the NEO community because it was
precisely this impact dust that was used in estimates by Chapman and
Morrison (1994) to calculate the threshold asteroid size for a global
catastrophe. I argue that these calculations are no longer valid and
that a new assessment of the impact hazard is needed."
--Kevin Pope, 25 January 2002

"I have been skeptical of the 'darkness at noon' scenario for
--Jay Melosh, University of Arizona

"The strong implication [of Pope's study] is that the impact
explanation of the K-T extinction will fall if the dust cloud hypothesis
--David Raup, University of Chicago

"Crucially, Pope ignores the social and economic knock-on effects of
such a global disaster. While we as a species would not become extinct as
a result of such an impact, it is almost certain that the world as a whole
would suffer to the extent of civilization collapse and Dark Age
--Benny Peiser, Liverpool John Moores University

"The incidence of asteroids about 1 km in diameter is estimated in
the order of one impact in 100 000 - 200 000 years. It follows that
some 20-30 such impacts occurred since humans appeared on this planet
about 4-5 million years ago - yet (to-date) the species survived.
--Andrew Glikson, Australian National University



    Andrew Glikson <>

    Kevin Pope <>

    Michael Paine <>

    David Johnson <>

    Daniel Fischer <>

    AAP, 25 January 2002


>From 24 January 2002

Airplanes more Dangerous than Asteroids, New Study claims

By Robert Roy Britt
Senior Science Writer

A new study claims the potential climate effects of an asteroid impact are
overstated and that a person's chances of death by asteroid -- commonly said
to be equal to dying in a plane crash -- are therefore lower.

The study directly challenges the prevailing view among leading asteroid
experts, and it has generated much interest and fresh debate. Some experts
said they simply did not yet know what to make of the new research.

The study does not change a basic equation: If an asteroid lands on your
head, you are dead. So might be thousands or millions of your neighbors if
the space rock is large enough. What the new research does question is the
widely held belief that the impact of a large asteroid would have global
repercussions, threatening civilization as we know it.

The study was done by former NASA scientist Kevin Pope, now of Geo Eco Arc
Research, and is detailed in the February issue of Geology.

In a telephone interview, Pope said the chances of any U.S. resident
suffering death by asteroid are about 1-in-100,000 instead of 1-in-20,000,
odds which are frequently cited by asteroid experts and equal to the risk of
dying in an airplane crash.

The odds of being killed in a car in the United States are about 1-in-100.

"It's still a very remote thing," Pope said of the asteroid threat, "but it
can happen."

Cosmic winter

Pope's work is based on new mathematical models and a review of scientific
literature regarding a thin, global layer of dust determined to be 65
million years old. The dust was generated when a roughly 6-mile-wide (10-km)
asteroid slammed into Mexico's Yucatan Peninsula, where a crater was found
more than a decade ago.

The regional effects would have been devastating -- no one argues that

But most researchers have assumed that the dust blotted out the Sun for
months on end, creating a "cosmic winter" that prevented photosynthesis in
plants -- the basic chemical transaction that supports most life on Earth.
Widespread extinctions resulted, including that of most dinosaurs.

Not everyone subscribes to the dust hypothesis, which is about 20 years old.

"I have been skeptical of the 'darkness at noon' scenario for years," says
Jay Melosh, a University of Arizona researcher who models asteroid impacts.

Melosh did not comment on Pope's study, but he said some researchers,
himself included, have shown that impacts might not generate enough fine
dust to have blocked the Sun enough to cut off photosynthesis. Only tiny
dust, which remains aloft longer than larger dust grains, could have such an

That's exactly what Pope's study concludes.

"The [previous] studies were in error," Pope says of work that supports the
cosmic winter hypothesis. "They really overestimated the effects of dust."

Threat to humans

Pope speculates on how his results might apply to impacts of smaller rocks,
which pose a more real threat because they are more likely.

While no immediate threat to Earth exists based on the present census of
asteroids, rocks are out there that will eventually hit the planet, Pope and
other researchers agree.

Asteroids larger than a half-mile (1 kilometer) are thought to hit Earth
once every 100,000 to 300,000 years. Most asteroid experts -- including top
NASA researchers -- have said that such an impact could cause global
devastation and might threaten human civilization, in part as a result of
climate effects on crop production.

"My new impact dust estimates indicate that death by an asteroid is far less
likely and that such medium-sized asteroid impacts would not have
catastrophic global effects," Pope said.

"This seems extremely over-optimistic and goes against a widely held
scientific consensus," said Benny Peiser, an expert on asteroid risk at
Liverpool John Moores University in the UK. "Crucially, [Pope] ignores the
social and economic knock-on effects of such a global disaster. While we as
a species would not become extinct as a result of such an impact, it is
almost certain that the world as a whole would suffer to the extent of
civilization collapse and Dark Age conditions."

Peiser said, however, that the new study is likely to stimulate vigorous
debate and trigger new research designed to further pin down the risks.

Kevin Pope doesn't entirely disagree with Peiser's assessment.

"There's a whole other set of processes that could be set in motion" by an
asteroid impact, he said, referring to potential economic consequences,
especially if multiple large cities were wiped out.

But as for a dust-induced cosmic winter, Pope said previous assumptions are
flawed. The data supporting such a worldwide catastrophe is only partly
based on dust from impacts, because such dust is hard to find. Researchers
have therefore used what's known about atomic bomb blasts to help support
the claim.

But it would take many atomic bombs to equal the effects of one large
asteroid. So researchers have to dramatically scale up the bomb data, and
Pope said this scaling creates errors.

Pope did not do any new field research. But his review of recent studies of
real impact dust, which he says were more revealing than previous studies,
shows that much of the dust in the layer is larger than had been thought --
too large to stay aloft long enough to generate the hypothesized climate


Pope's case is not airtight. And several researchers told they are
concerned the study may be flawed.

Pope examined patterns of coarse dust bits to create a model that showed how
the small dust particles were dispersed. To truly understand the influence
of impact dust, he says, scientists need to find a way to directly measure
the amount of small dust particles.

The work was made available to reporters in a press release put out Jan. 23
by the Geological Society of America. But scientists said that from what
they could see, the study did not appear promising, yet they needed more
time to fully digest Pope's full scientific paper, which they had not seen.

These researchers were dismayed that such a strong challenge to a
well-established idea was made available via a press release before they had
had time to read the actual scientific paper and thus be prepared to comment
on its validity.

"If you wanted to make a press release of this nature, you really ought to
notify some colleagues," said Alan Harris, an asteroid researcher at NASA's
Jet Propulsion Laboratory. After having discussed the press release and an
abstract of Pope's work with several colleagues, Harris said the jury was
still out on its merits.

Brian Toon, a University of Colorado atmospheric scientist, helped work out
some of the widely accepted notions that Pope's work refutes. Toon was also
part of a group that peer-reviewed, on behalf of Geology, an early version
of Pope's paper.

Toon recommended rejecting the paper for publication because, he said, small
dust particles "have no simple relation to large ones." He said it was akin
to saying "I saw a panther today, lions must be going extinct."

Toon said Geology did not let him see the final paper or Pope's responses to
his criticisms.

Bottom line

Amid all this uncertainty is one solid fact: The extinctions that occurred
65 million years ago are well documented by paleontologists. The fossils
exist in the same layer of soil where the dust is found, the so-called K-T
boundary that marks a division between Cretaceous and Tertiary periods of
geologic history.

Noted University of Chicago paleontologist David Raup has been embroiled in
these issues for more than two decades and now views it all from the
comfortable distance of retirement from active research.

"The strong implication [of Pope's study] is that the impact explanation of
the K-T extinction will fall if the dust cloud hypothesis falls," Raup told

Raup said there is a tendency to look at the dust cloud hypothesis as a
critical element in those extinctions. But he points out that many other
scenarios have been suggested. These range from the possibility of a global
firestorm fueled by an asteroid impact to climate change or acid rain not
necessarily related to any objects coming from space.

"Given the paucity of hard data, who knows which one to choose?" Raup

Indeed, if Pope's work is to be verified or refuted, there is likely some
more field work to do.

Copyright 2002,





After an impact event we also expect a great deal of rain. Rain will very
quickly wash fine dust particles into rivers and then the oceans. I would be
interested to know if the new skeptics have considered this. Where I live we
have very fine clay particles constantly washing into streams and lakes.
Does anyone know if Kevin Pope and his colleagues have considered the
mannerin which rainfall will moldulate the nature of the particles that are
preserved over geological time scales?

Gerrit Verschuur


>From Andrew Glikson <>

Dear Benny,

Not having as yet read the full paper by K. Pope ("Impact dust not the cause
of the Cretaceous-Tertiary mass extinction", Geology, 30, 99-102), the
following comments are based on the published abstract and on the GSA News
Release "The K-T Impact Extinctions: Dust Didn't Do It" (K. LeBeau, GSA News
Release No. 02-04).

At issue is the distinction between the effects on photosynthesis by (1)
atmospheric sub micrometer clay-dominated dust particles released from
asteroid-impacted rocks; (2) sub micrometer carbon-dominated sooth released
from impact flash-triggered fires; (3) sulphur and
nitrogen-dominated aerosols formed by flash-triggered oxidation and chemical
reactions between atmosphric gasses and impact-released components, and (4)
exothermic (heat releasing) condensation of impact-produced
silicate-dominated vapour due to volatilisation of target rocks. The
atmospheric effects of impacts (or for that matter volcanic eruptions) is
therefore HIGHLY CONFUSING, requiring specification in terms of relevant
physical and chemical processes.

If I read Pope (2002) correctly, there is no claim that atmospheric
consequences of impact were not a major reason for the K-T boundary
extinction, but rather that "He believes it may have been sulfate aerosols
produced from impacted rocks and soot from global fires that could have shut
down photosynthesis and caused global cooling." (K. LeBeau, GSA NR 02-04).
Differences in estimates of the relative balance between, and effect of, the
different "dust" components, ie. clay-dominated "dust", carbon-dominated sooth, sulphur and
nitrate-dominated aerosols - HARDLY JUSTIFIES such news item titles as "Alvarez-team was
wrong: K/T mass extinction not due to atmospheric dust loading (A.Yee, CCNet
24.1.02), or "The K-T Impact Extinctions: Dust Didn't Do It" (K. LeBeau, GSA
News Release No. 02-04), or indeed the title of the original article itself
"Impact dust not the cause of the Cretaceous-Tertiary mass extinction" (K.
Pope, Geology, 30, 99-102).

The effects of "dusting" on climate and the biosphere critically depend on
the residence time of dust in the atmosphere, which in turn depends on the
grain size, density and composition of the particles, atmospheric
circulation and other factors. Closely relevant are the studies by Toone
et al., 1982 (Evolution of an impact-generated dust cloud and its effect on
the atmosphere. Geol. Soc. Am. Special Paper, 190, 187-200), Melosh et al.,
1990 (Ignition of global wildfires at the Cretaceous-Tertiary boundary.
Nature, 343, 251-254) and numerous related contributions.

It must be borne in mind that final settling of the finest dust and sooth
components from stratospheric levels, where much of the long-term
sun-blocking occurs, will be delayed and the particles eventually
incorporated in sediments which occur above the main K-T boundary layer

Finally, I wish to comment on potential implications of the K-T extinction
event to modern risk factors from asteroid impacts:

1. The extreme density of biomass and hydrocarbons in modern urban
environments renders atmospheric carbon-sooth effects a principal risk
factor, whether due to asteroid impact or nuclear war - where radioactivity
represents a major additional factor.

2. The incidence of asteroids about 1 km in diameter is estimated in the
order of one impact in 100 000 - 200 000 years (for example see Verschuur,
G.L., 1996, Impact - The Threat of Comets and
Asteroids, Oxford University Press, plot on p. 165, based on Chapman and
Morrison, 1994, Nature 367, 33). It follows that some 20-30 such impacts
occurred since humans appeared on this planet about 4-5 million years ago -
yet (to-date) the species survived.

3. It follows that, rather than endangering the Human species as such, the
real danger of impacts is to the highly vulnerable urban civilisation with
its extreme concentration of biomass and its fragile structures (ie.
buildings, factories, power plants, nuclear facilities, fuel systems) -
given the scale of fires and sooth release from large cities and the
consequences of impact-triggered earthquakes (for a ~1 km asteroid -
earthquakes one or more orders of magnitude stronger than the most
destructive fault and volcanic-triggered earthquakes) ...

4. The proliferation of nuclear hair-trigger systems (ie.
Pakistan-India-type conflicts or Chernobyl-type accidents) suggest that the
self-destructive risks by Homo-Sapiens (so called) are orders of magnitude
more SERIOUS AND URGENT than natural hazards (volcanic eruptions,
earthquakes, asteroid impacts). It took an attack on two buildings in new
York on the 11 September, 2001, for the rest of the world to feel the

THE FLU ...!

Andrew Glikson
Australian National University
Canberra, ACT Australia

Geospectral Research
P.O. Box 3698
Weston, ACT2611 <>
ph/fax 61 2 6296 3853
Research School of Earth Science,
Australian National University,
Canberra, ACT 0200 <>
ph 61 2 6125 4076

>From Kevin Pope <>

Dear Benny,

Thank you for the chance to respond to your comments and those of Andrew
Glikson on my recent paper in Geology on asteroid impacts and the KT
extinction (Pope, 2002). First off, I apologize for the frustration that
Andrew Glikson and I know others have felt about not being able to comment
on the full paper. Copies (electronic) of the paper were available through
the Geological Society of America upon request in conjunction with the press
release they issued, however in reality, I now realize the news spread so
fast that many were left without access to the paper. I would be happy to
send copies to interested parties if they contact me at

The main issue that Andrew Glikson raises was dealt with in the full paper.
Dust was defined as clastic, pulverized rock fragments, and clearly excluded
soot, sulfur or nitrogen based aerosols, or silicate vapor condensates. So
there was no indiscriminant use of the word dust, nor was there any
confusion about what type of particle "dust" referred to. I had hoped that
most of this would have been clear from information in the abstract and
press release as well, since dust, vapor condensates, sulfate aerosols, and
soot were all at least mentioned as separate entities.  Granting this
clarification of the term dust, there is no confusion that the original
Alvarez et al., 1980 KT hypothesis for photosynthesis shutdown, and the more
detailed follow-up of this mechanism by Toon et al. 1982 mentioned by
Glilkson, all referred to the effects of dust as defined in my paper - not
soot, sulfate aerosols, or condensates. Therefore the major conclusion of
the paper - that this original hypothesis is not correct - is an accurate
statement of the conclusion.
Both Benny Peiser and Glikson correctly conclude that my paper does not
argue against photosynthesis shutdown, or atmospheric effects leading to an
impact winter, only that impact dust did not play a role in these putative
extinction mechanisms. Indeed, in my own work I have argued strongly that
sulfate aerosols produced by the vaporization of sulfur-bearing target rocks
at Chicxulub may have caused both photosynthesis shutdown and impact winter
leading to the KT extinctions (e.g., Pope et al., 1997). These sulfate
aerosols, combined with the rain of fire from reentering ejecta, are not
"rather questionable" extinction mechanisms, as Peiser asserts, but to the
contrary, I would argue that these are two prime candidates for causing the
KT mass extinction.

Turning to the implications of the Geology paper for smaller impacts, I am
afraid that Peiser's comments suffer from an over-interpretation of my work.
While I hope the NEO community takes note of my conclusions, it certainly is
not meant as an "attack" on NASA or the Spaceguard Survey (NASA funded my
research). As I understand it, the choice of the 1 to 2-km-sized asteroid as
a threshold in the Survey derives from a variety factors, including the
technological ease of detection, the economics of a complete survey, and the
threat of major destruction upon impact.  There is no doubt that a 1 to
2-km-sized asteroid would reek major destruction if it hit in or near a
populated area, or landed in the ocean (most likely) and generated massive
tsunamis. The point made in my paper is a very specific one - the dust
ejected into the stratosphere from such a mid-sized asteroid impact would
not have global catastrophic effects. This point is important to the NEO
community because it was precisely this impact dust that was used in
estimates by Chapman and Morrison (1994) to calculate the threshold asteroid
size for a global catastrophe. I argue that these calculations are no longer
valid and that a new assessment of the impact hazard is needed.
Unfortunately this 1-2 km threshold is deeply embedded in the NEO literature
without a full understanding of where the number came from, or the tenuous
nature of the calculations.  This brings me to my final point, Peiser
criticizes my paper for not "emphasizing our lack of knowledge and existing
uncertainties" and instead stressing that the "scientific community got it
completely wrong". Although I would not say completely wrong, previous
estimates of impact hazards are certainly flawed. My paper is but a small
step toward addressing these flaws, and much more work is needed.

Kevin O. Pope
Chief Scientist
Geo Eco Arc Research
Aquasco, Maryland, USA

Alvarez, L.W., Alvarez, W., Asaro, F., and Michel, H.V., 1980,
Extraterrestrial cause for the Cretaceous-Tertiary extinction: Science, v.
208, p. 1095-1108.

Chapman, C.R., and Morrison, D., 1994, Impacts on Earth by asteroids and
comets: Assessing the hazard: Nature, v. 367, p. 33-40.

Pope, K.O., 2002, Impact dust not the cause of the Cretaceous-Tertiary mass
extinction, Geology, 30, 99-102.

Pope, K.O., Baines, K.H., Ocampo, A.C., and Ivanov, B.A., 1997, Energy,
volatile production, and climatic effects of the Chicxulub
Cretaceous/Tertiary impact: Journal of Geophysical Research, v. 102, p. 21
645-21 664.

Toon, O.B., Pollack, J.B., Ackerman, T.P., Turco, R.P., McKay, C.P., and
Liu, M.S., 1982, Evolution of an impact-generated dust cloud and its effects
on the atmosphere, in Silver, L.T., and Schultz, P.H., eds., Geological
implications of impacts of large asteroids and comets on Earth: Geological
Society of America Special Paper 190, p. 187-200.

MODERATOR'S NOTE: Kevin, regardless of your estimates of atmospheric dust
loading due to asteroid impacts, estimates that are not shared by some other
experts in the field, my main criticism refers to your *general* claim (as
quoted in the GSA press release, 23 Jan 2002) that the impact of a 1-2km
sized object would be limited to a regional disaster but would not lead to
global catastrophe. I am concerned that such over-generalisations are
misleading and do not take into consideration other environmental and social
knock-on effects of massive impacts. I should add that we should also not
ingore the issue of cosmic dust loading due to the disintegration of or
impact by large comets given such events might very well be another
mechanism for a atmospheric and stratospheric dust loadings and cosmic
winters; BJP


>From Michael Paine <>

Dear Benny

I have just received a full copy of Kevin Pope's Geology paper but have not
had time to look at it in detail. The press release, however, gives the
impression that the global cooling effects of dust have been put forward by
others as the main damaging consequence of the KT impact. There are multiple
environmental effects from such a large impact that have been recognised
since the Alvarez explanation of the KT extinctions was announced. These are
best set out the following paper:

"Impact Mechanics and Implications for Extinction"
Authors: O'Keefe, J. D.; Lyons, J. R.; Ahrens, T. J.
Publication: International Conference on Catastrophic Events and Mass
Extinctions: Impacts and Beyond, 9-12 July 2000, Vienna, Austria,
abstract no.3142

The O'Keefe paper lists the numerous environmental consequences and their
likely durations. They note that dust effects were put forward by Alvarez et
al as a major mechanism but "the original mechanism of dust shielding
probably would not interupt photosynthesis for greaeter than ~one month.
INSTEAD, a stratospheric sulfuric acid aerosol haze contaminated by silicate
or pyrolized organic material COULD EASILY TURN OFF PHOTOSYNTHESIS FOR

Also I wrote an article about the dinosaur extinction for in which
I summarized the effects as: "So dinosaurs, if they were not consumed in a
firestorm, would have had to live through a torturous sequence of events --
from the barbecue to the freezer, to a dip in acid and then a hothouse

It concerns me that politicians wanting to dodge the Spaceguard issue will
use the media coverage of Pope's announcement to try and undermine the
credibility of the threat. Like you, I would dearly like the asteroid threat
to be shown to be greatly over-rated but my investigations of numerous lines
of research into the environmental effects of impacts convinces me that this
is not the case. More links are at:

Michael Paine


>From David Johnson <>

Dear Benny,

The recent article on CCNet regarding NASA and the question of has NASA over
stated the NEO Impact case. My response would be, I've yet to see NASA
overstate anything. With the largest NEO search programs in the United
States, and some serious investigations sponsored by NASA to take
closer looks at Near Earth Objects it would appear that most other
Governments are still ignoring the reality of the threat, and the general
populous of the planet doesn't even know that there is some truth in the
movies they have seen (Deep Impact and Armageddon, for two), yet in the
United Kingdom, it would appear that the reality of the threat has been
realized, and appropriate action taken.

The problem is that the Governments of our world see little value in
defending the planet from something which may not occur for decades. Yet the
NASA program is primarily concerned with the larger NEO's of 1KM or larger.
These objects have a longer duration between incidents, whereas the smaller
objects are more frequent, and more likely to impact the Earth. It is the
smaller NEO which poses more of a threat, and in harder to track, as they
are also much faster, thus there threat is much greater, and unpredictable.

The reality of the threat is that we may only have 3 minutes or a hundred or
even a thousand years left to live. The much larger question is, what are we
as a civilization going to do, continue on as we are currently, more
interested in fighting amongst ourselves or work together, and find a way to
defend the planet we call home.

The UN has taken some interest in this, yet the UN has no real power to
effect change or force things, and it has a very questionable track record
in even resolving disputes, or even keeping the peace. However, the UN is
good at diplomacy, wherein most scientist make very poor diplomats.

NASA on the other hand has yet to evolve from its Cold War birth and
attitude, and into the 21st century. There appears no difference at present
between the 20th and the 21st centuries, merely an extension.

The Spaceguard Program is the first program in human history which truly
does need Government sponsorship and funding, as for the first time in our
history it is a program which truly means the safeguard the survival of
mankind. As the Spaceguard Foundation nears its first decade of existence,
many may question weather it has had any effect or not. It has opened a lot
of eyes and ears, but mostly within the scientific community, and not

I have ask various U.S. Government Officials over the past few years just
how much the survival of our way of life is worth. I have yet to receive an
answer. The current administration I've found is not any different than the
last when it comes to issues posed by the Spaceguard
program. Thus the only response we may see to the positive will be only
after an object has been identified as an actual impactor.

Without the aid of an advanced warning system as proposed by Spaceguard,
mankind's longevity is truly numbered, and the long night of oblivion and
extinction is what we may have to look forward to. Perhaps at some point in
the future, an Alien civilization tracking our radio signals will arrive at
the Earth to find it a desolate lifeless planet, with only a trace of it's
past inhabitants, and they will wonder why we disappeared and died off. The
truth will be that we were to ignorant and self-absorbed and ignored the
threat of extinction. These visitors will leave, scratching there heads, and
questioning the existence of other intelligent life forms.

For a civilization that professes to love life, we are at times extremely
unintelligent and wasteful in how we handle problems.

Has NASA overstated? No, as a matter of fact I would say they need to be
more forceful where Governmental officials are concerned, to the point that
these officials truly understand that life is in peril on this planet we
call home, and that - in the long-term - we do in fact face extinction,
unless the research is funded and defense systems are developed, our chances
surviving to the next millennium are much less than we can even speculate

The answers are education, not only of governments, but of all inhabitants,
and an implementation of a comprehensive Spaceguard program, to include
searches in ALL hemispheres (Southern as well as Northern), as without eyes
is every hemisphere, the usefulness of an early warning system is

David James Johnson


>From Daniel Fischer <>

The German TV science program "nano" had a report on Jan. 23 on the imminent
completion of the first 6-meter liquid mirror telescope in Canada - and
while it's purpose are cosmological surveys, it was stressed that this LMT
will also hunt for faint NEOs, in order to provide long early-warning times
before impacts. No further details about the search strategy were given, nor
was it revealed whether the NEO search will run concurrently with the galaxy
surveys, i.e. all the time. has a
summary of this item (in German), plus some links (mostly in English).


>From AAP, 25 January 2002,4057,3650415%255E2761,00.html

A CATASTROPHIC asteroid crash which triggered earthquakes around the world
and wiped out huge swathes of life may also have contributed to Western
Australia's huge mineral resources, scientists believe.

The 120km-wide Woodleigh crater was discovered accidentally by WA Department
of Mineral and Petroleum Resources (DMPR) worker Robert Iasky as he was
drilling for coal near Shark Bay, 650km north of Perth.

When Iasky's team drilled down into the crater, buried under up to 600
metres of rock and sand, they found a huge chunk of dense granite that had
been dragged upward as the ground rebounded when the asteroid hit.

DMPR mineralogist Franco Pirajno analysed samples of the granite and found
valuable elements such as magnesium, copper, chromium and nickel, which are
unusual in this kind of rock.

Pirajno believes that instead of vaporising and spreading through the air
over a wide area, the asteroid's components must have been crushed into the
surrounding hot granite.

"It must have created one hell of a bang," Pirajno told New Scientist

Gold deposits may also have formed as streams of hot water ran through
cracks in the rock.

The Woodleigh asteroid was about five kilometres wide when it slammed into
the Earth 360 million years ago, sparking volcanic activity around the globe
and causing a dust cloud which blocked out the sun.

It is the fourth largest asteroid collision ever discovered on Earth and
would have been almost as big as the Mexican Chicxulub collision that is
thought to have wiped out the dinosaurs 65 million years ago.

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