[meteorite-list] Hyperbole in Media Reports on Asteroids and Impacts

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Fri, 04 Jan 2008 23:16:36 -0500
Message-ID: <t31un3l15e30258i09i71lkq3tjc8q3nuf_at_4ax.com>

A few years old, but a good read.

http://csicop.org/si/2005-03/asteroids.html

Hyperbole in Media Reports on Asteroids and Impacts
News releases and media reporting on asteroid impact-related science frequently
exaggerate the uniqueness and significance of new research. We should be
skeptical of all claims of scientific revolutions.

David Morrison



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Many observers of the science press have noted an increasing tendency for both
news releases and printed stories to exaggerate the uniqueness and significance
of new research. The writer of a news release does this to increase the
probability that the media will cover the story, and the media reporter will go
along with this hyperbole or perhaps expand it further to get the story approved
for publication by editors or other gatekeepers.

The field of impacts (and impact hazards) is not immune to these trends. In my
NASA-supported Web page http://impact.arc.nasa.gov, I try to apply a filter to
reduce the noise level in media reports, which would otherwise overwhelm much of
the real science.

This is not intended as a general criticism of science reporting. There are many
excellent science journalists who understand the issues and provide
well-reasoned discussions of context for news stories. Overall, the reporting by
science journalists of impact-related stories has been excellent. But a
hyperbolic headline added without their knowledge can sometimes catch even the
best writers.

Background on Asteroids and Impacts
In his excellent book Mysteries of Terra Firma (Free Press, 2001), geologist
James Powell discusses three revolutions in our understanding of Earth history.
The first, responding primarily to the discovery of radioactivity at the end of
the nineteenth century, was the concept of deep time-measurement of the age of
Earth and dating of the primary geological and evolutionary events in its
history. The second revolution dealt with the discovery of plate tectonics,
first suggested (as "continental drift") but subsequently rejected early in the
twentieth century. Plate tectonics was accepted only in the 1960s (when a wide
range of strong new evidence was obtained) and has become the fundamental theory
for understanding the dynamics and history of the Earth's crust. The third
revolution was the space-age recognition of the role of cosmic impacts on
geology and evolution.

Scientists are still exploring many implications of this third revolution. Space
exploration missions to other worlds and careful scrutiny of impact landforms on
Earth have revealed that cratering is a universal process in the solar system.
The pioneering work by Walter Alvarez and colleagues on the end-Cretaceous mass
extinction further showed that cosmic impacts can have profound influences on
the evolution of life. Whether other mass extinctions are also due to impacts
remains an open question.

My own interest in impacts includes the contemporary danger from asteroids
colliding with Earth. Although the probabilities are low, a devastating impact
capable of killing hundreds of millions of people could happen at any time. The
NASA Spaceguard program, which seeks to find any threatening asteroid in time to
mitigate the impact (preferably by deflecting the asteroid away from Earth), is
one response to a growing awareness of the impact problem.

Did the KT Impact Cause the Extinction of the Dinosaurs?
The KT (Cretaceous/Tertiary, 65 million years ago) extinction is by now an old
story, but sometimes the news media still report dramatically opposed
conclusions as if a major debate existed to this day. Certainly the issue was
contentious when impact extinction was first proposed by the Alvarez team
twenty-five years ago, but a scientific consensus had emerged by the early
1990s. This progress of the Alvarez theory, increasingly supported by new
evidence (such as the discovery of the Chicxulub Crater in Mexico), has been
chronicled in several excellent books, such as Night Comes to the Cretaceous by
James Powell, T. Rex and the Crater of Doom by Walter Alvarez, The End of the
Dinosaurs by Charles Frankel, and When Life Nearly Died by Michael Benton.

In spite of the scientific consensus, there was substantial media coverage in
2004 of alternative hypotheses of dinosaur extinction. Major stories have arisen
from the work of paleontologist Gerta Keller at Princeton, who has been
challenging the impact theory for more than two decades. Recently she has
decided that impacts may indeed be implicated, but probably not the Chicxulub
impact (just off the coast of the Yucatan peninsula, the impact most earth
scientists think is primarily responsible). One hypothesis she has suggested is
that while the 100-million-megaton energy Chicxulub impact was insufficient to
kill the dinosaurs, a smaller impact 300,000 years later may have done so.
Princeton University frequently issues news releases on her work, and sometimes
the publicity gets out of hand, with bold headlines such as "KT Mass Extinction
Debate Wide Open and in Full Swing," "The Space Rock Was Framed: Asteroid
Cleared in Dinosaurs' Death," and "Asteroid Couldn't Have Wiped Out Dinos."

One characteristic of media hype is to suggest that all science dealing with the
KT extinction is about dinosaurs. Dinosaurs are popular. But dinosaur fossils,
which are relatively rare, do not define the mass extinction boundary, which is
precisely marked in the marine fossil record by changes in single-celled
protists, as well as by the global layer of extraterrestrial material and
shocked quartz from the impact.

On the other hand, some scientists discuss the dinosaur extinction without
reference to the simultaneous global mass extinction in which more than half of
all biological families were lost. This attitude is reflected in the remark by
paleontologist David Penny that "We agree completely with the geophysicists that
an extraterrestrial impact marks the end of the Cretaceous. But after
twenty-five years [scientists] have still not provided a single piece of
evidence that this was the primary reason for the decline of the dinosaurs." [1]

Most scientists consider it to be exceedingly unlikely that the dinosaur
extinction was unrelated to the global KT event. In addition to the coincidence
in time and increasing evidence that the dinosaur extinction was abrupt, we
think we understand how the Chicxulub impact killed large land animals by a
combination of brief global firestorm followed by months of cold. Neglecting
this relationship is one fatal flaw in this year's widely reported hypothesis
that dinosaurs went extinct because of disparity in the numbers of males and
females born. Perhaps in this case the publicity was stimulated by the word sex,
as in the Washington Times headline "Why Dinosaurs Died-It's All about Sex."

An Impact-caused Extinction 250 Million Years Ago?
Was the end-Permian mass extinction caused by an impact? No one knows, even
though the PT event (Permian/Triassic, 252.6 million years ago, a newly
published, more precise date for the prime extinction) was the greatest of all
mass extinctions, with more than 90 percent of families becoming extinct. The
past year has seen several new scientific results, many associated with claims
and counter-claims concerning the submarine Bedout impact (or non-impact)
structure that might (or might not) be the "smoking gun" crater. Also widely
reported have been evidence of extraterrestrial material (but not iridium or
shocked quartz, so far) at the PT boundary, and recent indications that the PT
extinction may have been two sharp events separated by several million years.

I have no quarrel with the media coverage of these issues, except where news
releases claim that the question has been definitively solved. There is no
consensus concerning the cause of the PT extinction, and hence every reason to
follow the debates as they happen. For example, I will be interested in results
from a blind test for evidence of an impact that is being conducted by a team of
scientists using new samples from China, where an excellent cross- section of PT
rocks is accessible.

Meteorites and Fires
Meteorites do not cause fires. Yet it is common to find news reports that a
bright meteor fell and started a fire. Often the existence of a fire is quoted
as evidence that the meteor struck the ground (thus making it a meteorite).

In 2003, the old idea that both the Great Chicago Fire of 1871 and another
conflagration more than a hundred miles north in Wisconsin were started by hot
stones falling from the sky was revived. This coincidence seems striking, with
two of the most destructive fires in U.S. history happening at the same time-but
the coincidence might also be related to extreme dryness and high winds across
the upper Midwest.

In the cases where we have been able to estimate the surface temperature of
just-fallen meteorites (such as where they land on snow or ice), the data
indicate that they are cool. Nor should this be surprising: the violent heating
of the stone's surface by atmospheric friction lasts only a few seconds,
followed by several minutes of free-fall through the cold stratosphere. I follow
the rule of thumb that if a meteor or meteorite is reported to have started a
fire, the claim is probably mistaken. These are "meteorwrongs," not meteorites.

The Recent Impact Rate
A common assertion in the tabloid press and on some Web sites is that we are at
great risk from impacts, because impacts happen much more frequently than the
scientists claim. Usually the argument is related to supposed evidence for
recent large impacts.

One report (from The Guardian, on August 19, 2004) concerned huge craters under
the Antarctic ice sheet said to be caused by an asteroid as big as the one that
wiped out the dinosaurs, but striking about 780,000 years ago. The newspaper
reported that an asteroid measuring three to seven miles across broke up in the
atmosphere with five large pieces creating multiple craters over an area
measuring 1,300 by 2,400 miles. Supposedly this impact caused a reversal in
Earth's magnetic field (a highly suspect claim) but little other damage.
Obviously the description of this event is inconsistent with what is known about
cosmic impacts, yet this "discovery" was reported seriously.

The "Sirente crater," a lake near Abruzzi, Italy, has also been widely
speculated to be an impact from the Roman period. If this were true, Sirente
would be one of the most recent craters on Earth, falling right next door to the
capital of the Roman Empire. However, no meteoritic material has yet been
recovered from the lake. In 2004, an article in Tumbling Stone magazine suggests
that this is an anthropogenic feature and not the result of an impact.

The Web site of Astronomy magazine published a report in October 2004 on
identification of a field of meteorites and impact craters near Lake Chiemsee in
southeastern Bavaria, Germany. This crater field, which falls within an ellipse
58 by 27 km, is said to hold at least eighty-one impact craters ranging from 3
to 370 meters in size. The authors, using historical and archeological evidence,
conclude that an asteroid or comet fragment exploded above southeastern Germany
in the Celtic-Roman period, probably around 200 b.c. They estimate that the
projectile had a diameter of about 1 km. Since the authors are primarily amateur
scientists and their work has not been published in a refereed journal, it is
difficult for me to judge these conclusions, in terms of either the
identification of impact craters or their probable date of formation. Another
report, discussed below, suggests that there are many very dark, unseen comets
that constitute a previously unrecognized threat.

In assessing the reliability of such stories, we should note that even one of
these recent mega-impacts is unexpected from known impact rates, which are based
on both astronomical observations and the long-term cratering history of Earth
and Moon. (These impact rates might be off by a factor of two, but certainly not
by a factor of ten or more.) For example, the Lake Chiemsee impactor is claimed
to have been about 1 km in diameter and to have struck within the past 2,500
years, whereas on average an asteroid or comet this large hits Earth only once
in about 500,000 years. While any one impact might be true (as a statistical
fluke), it is hard to believe that several of these stories are correct. I
remain skeptical.

Super-dark "Stealth" Comets
A new report in Monthly Notices of the Royal Astronomical Society by W.M.
Napier, J.T. Wickramasinghe, and N.C. Wickramasinghe is titled "Extreme albedo
comets and the impact hazard." Based on a dynamical argument, they conclude that
there should be more than 1,000 times more Halley-type comets than are actually
observed. They therefore suggest that the comets become invisible, and that the
impactor population is dominated by bodies too dark to be seen with current
astronomical surveys.

One should be skeptical of a theoretical result that has no data to support it.
One should be even more skeptical if it seems inconsistent with the data we do
have, resolved (in this case) only by postulating a new class of "invisible"
comets. But further, the idea that our astronomical surveys might miss huge
numbers of such "stealth" objects is largely beside the point. We know about the
low comet cratering rates from the dearth of small craters on Jupiter's Galilean
satellites, especially Europa. From this perspective it seems clear that there
is not a large population of stealth comets to worry us.

Proposed Rain of Mini-comets
In the late 1980s, the proposal of a tremendous flux of tiny comets (each no
bigger than a bus) was widely discussed in the science media. The discoverer was
a well-respected space scientist from the University of Iowa, Lou Frank, who was
attempting to interpret very small, transient dark patches in NASA spacecraft
images of Earth's atmosphere. Frank hit upon the idea that these dark spots were
due to bursts of water vapor liberated in the upper atmosphere by disintegrating
small comets, a hypothesis that he advocated at meetings of the American
Geophysical Union, in published papers, and directly to many science
journalists.

In spite of the excellent reputation of their advocate and invocation of NASA
satellite data, an intense rain of such mini-comets was quickly recognized by
most scientists as inconsistent with a wide range of other observations. The
numbers of impactors proposed by Frank were a million times higher than the
known flux of objects with their proposed mass. They would have to be so black
that they were invisible to telescopes. Since their atmospheric impacts were
also not being seen as meteors or flashes of light, they must also carry little
energy. (The absence of a flash was later confirmed when data were released from
sensitive surveillance satellites that constantly scan Earth from above.) They
also evidently did not make craters when they struck the Moon. Finally, the
amount of water vapor they would dump in the upper atmosphere was inconsistent
with the known dry conditions in the stratosphere.

Although many scientists assumed that the dark spots were just noise in the
spacecraft detector, they were unable to work with the raw data to verify this
speculation. The media story persisted, aided by NASA news releases supporting
the mini-comets. While they shook their heads in wonderment, few of Frank's
colleagues wanted to challenge him personally. His advocacy of mini-comets
became an obsession-he even wrote a book called The Big Splash to market his
ideas directly to the public. There seemed to be no polite way to make the story
go away. One scientist tried, however, to counter with humor, when he proposed
that the mini-comets be called Louis A. Frank Objects, or LAFOs.

Impact News in Great Britain
Based on the large sampling of press reports from both sides of the Atlantic
collected by anthropologist Benny Peiser of Liverpool John Moores University,
there seem to be significant differences in the press treatment of impact
science stories between the United States and the United Kingdom. Many British
science reporters like to play such stories for their humorous possibilities, as
opposed to the straight science reporting that is standard in America.
Ridiculing the "boffins" seems to be a popular way to treat scientific
controversy. Another approach is to start off a story in a hyperbolic vein, only
tempering the initial overstatements several paragraphs down. For example, an
opening assertion might be made that an asteroid is on a collision course with
Earth, but a few paragraphs later it is revealed the the probability of the
impact is only one in 100,000. My impression is that the British reading public
does not take this very seriously, and that their news reporting in general is
intended to be more entertaining. A problem can occur, however, when such
stories are picked up in other countries, where this tongue-in-cheek tone might
be taken seriously. Let the reader beware.

Space science research dealing with impacts often makes a good story, especially
when it is controversial. The public is likely to find science more interesting
if they realize that research is carried out by real people working in a
competitive environment. The controversy is very real in some cases, such as
finding the cause (or causes) of the great PT mass extinction. In other cases,
such as the KT mass extinction and the contemporary rate of impacts on Earth, a
consensus exists based on multiple lines of evidence. While there are still many
media-worthy stories, we should be skeptical of reports that the consensus has
been overthrown by a single new result.

As Carl Sagan often said, "extraordinary claims require extraordinary evidence."
A similar admonition might be that before revolutionary theories are widely
publicized, they need to be given a reality check. This is best done by the
scientists deciding whether to issue a news release. But if the scientists are
not self-policing, the burden falls upon the journalists to filter the signal
from the noise, or upon the skeptical attitude of the reader.
Received on Fri 04 Jan 2008 11:16:36 PM PST


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