CCNet 65/2001 - 9 May 2001

"We are now working on an experimental project on how to get more
public support for NEO activities. During our NEO observations, there are
many moving objects (asteroids) in our wide field images. If we can prepare
and distribute good software to detect these moving objects and several
wide field images, interested people, who receive them, can detect a
number of these objects. Last winter, we asked interested amateurs who would
work on this project with the help of Yomiuri Newspaper Company and
received a number of applicants. It became a contest how many asteroids
they could detect. This was carried out using their computers, and 133
teams reported. They now understand how astronomers detect moving
objects. We find that this is a very effective way to highten public
interest and support for NEO activities. The Japan Spaceguard Association
intends to expand this project now to an international level with the help
of the British Council (Tokyo office).
--Syuzo Isobe, Japan Spaceguard Association, 8 May 2001

"To the conservation biologist, there is little positive to be said
about extinction. From an evolutionary perspective, however, extinction is
a double-edged sword. By definition, extinction terminates lineages and
thus removes unique genetic variation and adaptations. But over geological
time scales, it can reshape the evolutionary landscape in more creative
ways, via the differential survivorship of lineages and the evolutionary
opportunities afforded by the demise of dominant groups and the
postextinction sorting of survivors. The interplay between the
destructive and generative aspects of extinction, and the very different
time scales over which they appear to operate, remains a crucial but poorly
understood component of the evolutionary process."
-- David Jablonski, Proc. Natl. Acad. Sci. USA, May 8, 2001

    Spaceguard Central Node, 8 May 2001

    Brian G. Marsden <>

    Syuzo Isobe <>

    Harvey Leifert <>

    Daniel Spires <>

    Michael Paine <>

    Andy Smith <>

    Proceedings of the National Academy of Sciences of the USA, 8 May 2001

    SpaceDaily, 8 May 2001


From Spaceguard Central Node, 8 May 2001

1998 KM3

The identification of 1998 KM3, which was announced on MPEC 2001-J05 by the
Minor Planet Center, is the result of a successful international
collaboration among different Institutions.

The recovery of this lost PHA is very important for two reasons:

According to recent results by Milani (April 2001, Risk Page of NEODyS ),
1998 KM3 had some remote probabilities to impact the Earth within the
current century. Several virtual impactors were identified using the 1998
data. Also, being about 400 meters in size this was a serious case.

This case is a demonstration of the potential offered by an international
coordinated effort when there is the need to deal with very difficult

Before going into some of the details, let's look back at the original
message announcing this observing campaign.

The following informative message was posted on the New Announcement list of
the SCN and sent to the Minor Planet Mailing List on November 24, 2000.

On behalf of the Spaceguard Central Node, we want to draw your
attention on a very interesting PHA, 1998 KM3, which was recommended by
Andrea Milani. According to his calculations, 1998 KM3 has the
potential to approach the Earth as close as two Earth radii in the
course of a close encounter in 2083. No collision solutions have been
detected so far.

There is one problem: 1998 KM3 is virtually lost.

Even though a targeted search would not be impossible in principle,
given the means available to NEO community, we don't think it is
worth to ask for investing a huge amount of efforts, at least at this

According to the present orbital knowledge, there might be a close
encounter with the Earth in early December 2000, followed by
favourable observing conditions for the rest of month and eventually part
of January 2001. It is very likely that 1998 KM3 will be accidentally
rediscovered by the big NEO survey programs sometime in December. Magnitude
peak of the apparition ranges from about 12.5 - 13 V to about 19.5 -
20.0 V. It is obvious that it might escape detection if it is on the
"wrong side" of the apparition, but this case serves as a good test for
the survey programs. We hope that data on newly FMOs could be made
available to the community as soon as possible.

If, indeed, it will pass unobserved by the end of December,
follow-up actions might be considered using the "negative" information.

Thank you for your attention and good luck!

Some highlights about this identification

This big challenge of this case is that 1998 KM3 was lost. As soon as this
announcement was made, we produced 200 possible orbits for 1998 KM3 using
the multiple-solution method with the Orbfit software. The coverage of the
confidence region was stopped at the 5-sigma level. Near the time of the
close approach the sky uncertainty was of the order of 100 degrees!

The situation became difficult from the start: after the close encounter
early in December and the following dark moon period at the end of the
month, 1998 KM3 had still to be found. To make sure that KM3 did not escape
detection, we operated in two ways: a) To check all NEO candidates on the
NEO Confirmation Page whose angular rates/positions could be compatible with
this object. b) To use the MPC service called MPChecker in order to cover
all the sky regions at appropriate dates in which the target could have not
been discriminated from MBOs. All the new objects/designations at
appropriate positions were checked for rates similar to those expected for
1998 KM3.

Neither of the two checks was successful.

We then concluded that 1998 KM3 was probably not on the side of the close
encouter, but on the other side of the confidence region. However, the
object would have been significantly fainter on this side, no detectable or
marginally detectable by surveys like LINEAR, LONEOS or NEAT.

With these results, the following month we asked Robert McMillan, PI of the
Spacewatch project, if he could arrange some sky coverage of the faint side
of the confidence region. Not only he agreed, but, later on, he was willing
to extend the search further respect to our initial request. A detailed plan
was put into action, taking advantage of the fact that the sky uncertainty
was about the half of that of December while its visual magnitude was still
within the capabilities of Spacewatch.

The coverage of the confidence region was made by J. Montani on January 19,
by A. Gleason on Jan. 20 and 21, by R. McMillan on Jan. 22 and by J. Larsen
on Jan. 25 and 26. J. Scotti provided some preliminary blinking of all the
Spacewatch regions (many degrees long up to the 21.0-21.5 magnitude). The
result of this effort was to cover from -0.5 to + 4.7 sigma, but, to our
surprise, no candidates for 1998 KM3 were found. To secure the value of such
an effort, hand blink of all the regions was provided by Arianna Gleason
around mid-March confirming the negative results.

The negative results of Spacewatch were crucial to conclude that in fact
1998 KM3 could only be on the side of the close enounter and that for some
unknown reason could have been missed.

In the meantime, Andrea Milani and his team at the University of Pisa
upgraded their software and extended the monitoring for possible collisions
beyond the year 2050. Results of this work were recently posted on the Risk
Page of NEODyS by Milani: unfortunately the hazard posed by 1998 KM3 was
more serious than previosuly expected. Several collisions were found; two of
them, in 2071 and 2076, were particularly relevant with probabilities above
one in a million.

Given the new situation, two plans could be set-up:

a) Re-analyze the work done by the big surveys and study what margin
of success existed.

b) Organize a last-minute campaign for virtual impactors, in a
similar fashion to the plan    made for 1998 OX4.

We started with plan (a): a more detailed analysis was made of the sky
coverage plots from LINEAR and LONEOS in December using the asteroid
services site at Lowell Observatory. This allowed to flag several
opportunities for each orbital solution not covered by Spacewatch (using the
initial sample of 200 orbits). After noticing that every orbital solution
had been covered at least on one night, we sent two separate messages to G.
Stokes for LINEAR and T. Bowell for LONEOS, explaining that 1998 KM3 should
have been on one or more of their images/data. We indicated a few specific
nights and asked them how to retrieve such information.

G. Stokes replied immediately to our message and contacted Brian Marsden at
the MPC since there was a reasonable chance that 1998 KM3 could be hidden
among unchecked data in MPC archives. In fact, 1998 KM3 was identified using
data from this resource on three different nights among the data of LINEAR.
We also received a very positive answer from T. Bowell and B. Koehn
regarding the LONEOS data: it turned out that the real orbital solution was
not covered by LONEOS.

Apparently, LINEAR missed 1998 KM3 on December 5, during the close
encounter, probably because it didn't image the right region at the right
time: 1998 KM3 was in fact moving very fast on that night.

As a final remark we would like to add that the key to the success of this
campaign has been the large effort made by the Spacewatch team who made a
targeted search over a very large region of the sky.

Andrea Boattini, Germano D'Abramo, The Spaceguard Central Node, May 8, 2001,
Rome, Italy


From Brian G. Marsden <>

It was a pleasure to read the account by Andrea Boattini of the
successful collaboration on the 1998 KM3 recovery. In contrast, to read
elsewhere in the internet of statements that the Minor Planet Center was
somehow to "blame" for the time wasted by Spacewatch in unsuccessfully
searching for the object a month after it was "recovered" shows that some
colleagues have
a rather imperfect knowledge of how astrometric observations from NEO
surveys are treated.  Because there is no facility at most of the surveys to
link together the observations of what appear to be main-belt objects (and a
typical night's imaging will produce some 200 times as many of these as it
does of candidate NEOs), this linkage is done on their behalf by the Minor
Planet Center. Sure, the MPC also does a fair bit of work on unusual objects
like NEOs and TNOs, but the bulk of its work is on MBOs, because the bulk of
the images are of MBOs. Given that there may be 30,000 or more observations
on a single night, this night-to-night linkage can be an almost intractable
problem, given that many days may elapse between the separate nights of
observations of the same field. The Spaceguard Central Node, which has about
the same number of employees as the Minor Planet Center, is designed
specifically to work on NEOs. Since it therefore has 200 times fewer objects
to work with, and it in fact needs to work only with objects for which the
initial information has already been correlated and provided by the MPC, it
can therefore afford to scrutinize the situation with regard to each NEO
very carefully. The SCN has indeed been doing this work admirably, in
particular by finding numerous precovery observations on old photographs
that therefore allow dramatic improvement of the NEO orbit solutions. In
turn, these new solutions will almost invariably allow the complete removal
of the candidate impact computations from the Risk Page of the NEODys,
another organization that can afford to concentrate only on NEOs and that
often acts in concert with the SCN.

     Andrea Boattini notes that he asked Spacewatch in January to make a
specific search for 1998 KM3 _after_ he had checked that the object had
shown up, neither on the NEO Confirmation Page nor among the 5000 or so new
multiple-night objects designated by the MPC in December. Indeed, he
confirmed that 1998 KM3 was not there, a conclusion that had previously been
quite evident to the MPC. It is in fact a pity that he then felt that his
principal need was to contact Spacewatch, because it is indeed a shame that
Spacewatch was then obliged to make the search. If he were eager to have
1998 KM3 recovered, January was the time when he should instead have
computed the 200 variant orbits he discusses, at which point he could have
informed the MPC of the nights when the search programs were likely to have
recorded the object. The MPC did not in fact receive this information until
May 3, and the MPC received it then only because that was also the day
Andrea gave it to Grant Stokes, who immediately passed it on to the MPC as
the organization entrusted to make the night-to-night linkages.
Specifically, Andrea suggested that LINEAR might have the object on 2000
Dec. 21 and Dec. 30. This information from Andrea was indeed very helpful to
me, because it then took me only a matter of minutes to notice that there
was an object with large but roughly comparable departures from the 1998 KM3
orbit on these two nights. It took only a minute or two more for me
unequivocally to verify the two-night identification by linking these 2000
observations to those in 1998. At the same time, I could also identify
further LINEAR observations on 2001 Jan. 3, a night that had not been
mentioned by Andrea but that had already shown up as a single-night
detection (although the correct object was not clear) in my own initial
calculations. After checking back with Grant, who immediately then responded
to Andrea, I published all the recent observations and my new orbit
computation on MPEC 2001-J05. A fine collaboration indeed, and the only pity
is that it was initiated on May 3, rather than in, say, mid-January. 1998
KM3 was not "recovered" in December: it was recovered on May 3. I also
verified that the 0.021-AU approach to the earth on 2000 Dec. 3 was by far
the closest to occur during the 80 years after the object's discovery: there
was no possible earth impact.

     Why did the MPC not realize previously that there were multiple nights
of the same object?  The nine-day separation between the pair of nights
noted by Andrea is really too long to do this in any sure way. The four-day
separation between the second and third nights ought to have been a better
choice. The motions of the object on these nights individually showed that
the object was somewhat unusual, but only in the sense that each object was
likely to have a basically main-belt orbit with a somewhat high
eccentricity. But in that case the two nights would not link together, for
to do that one would have to know that the object had its perihelion inside
the earth's orbit, and such objects are rare, even among NEOs. So, given
that there was a host of other objects around to confuse matters, it is
really not surprising that this linkage was missed. As for Dec. 21, it is
interesting to see that the motion was perfectly main-belt, even though the
object was only 0.2 AU from the earth.

     No, the only way this recovery would reasonably have been made is the
way the recovery actually happened. One had to start by carefully examining
the 1998 KM3 orbit, as Andrea did.  With the information that LINEAR
observations would be likely on the two nights indicated, the rest was quite
straightforward. I note that much the same happened with 2000 SG344, except
that the essential communications were lost at the time. This kind of
collaboration between the MPC and the SCN is indeed to be welcomed, and I
hope it happens still more smoothly in the future. 


From Syuzo Isobe <>

Award for an NEO Observer by the Japan Spaceguard Association

As was mentioned by CCNet, the Planetary Society has given awards for five
NEO observers in 2000. This is a good way to support world-wide follow-up
teams. The Japan Spaceguard Association started its activities in 1999 as a
non-profit organization registered to the Tokyo Metropolitan City and also
tried to give an award for an NEO observer. The Association has received two
applications and its committee chose Mr. Taku Maeno, at the Mitoko
Observatory in Tokushima prefecture, Japan.

At the annual meeting of the JSGA held on March 31, 2001, Taku Maeno was
awarded 400,000-yen ($1=\125) for his contributions in NEO follow-up
observations. The JSGA intends repeat this award activity every year and
make it expand year by year.

One of effective ways how to get public supports for NEO activities

The NEO hazard problem is a serious one for human-being. However, it is not
well understood by the wider public although many active people on this
problem, including those on CCNet, are making great efforts. Since NEO
collision probabilities are very low, people do not realize the inherent
hazard - until it really happens.

The Japan Spaceguard Association is working in different ways to make the
public realize the general problem. It publishes a journal regularly and
distributes it to the public. It arranges public lectures several time per
year. It produces its logo badge and member cards. However, these efforts
work rather slowly.

We are now working on an experimental project on how to get more public
support for NEO activities. During our NEO observations, there are many
moving objects (asteroids) in our wide field images. If we can prepare and
distribute good software to detect these moving objects and several wide
field images, interested people, who receive them, can detect a number of
these objects.

Last winter, we asked interested amateurs who would work on this project
with the help of Yomiuri Newspaper Company and received a number of
applicants. It became a contest how many asteroids they could detect. This
was carried out using their computers, and 133 teams reported. They now
understand how astronomers detect moving objects. We find that this is a
very effective way to highten public interest and support for NEO
activities. The Japan Spaceguard Association intends to expand this project
now to an international level with the help of the British Council (Tokyo

In the UK, Liverpool John Moores University collaborates with the JSGA, and
both Japanese and UK schools will become sister schools for this project,
each of which will represent a team in the contest for moving objects

The JSGA hopes readers of CCNet will support these activities. You can find
related papers at


From Harvey Leifert <>

The irregular asteroid Braille (also known as 1992 KD) was discovered in May
1992. Deep Space 1 (DS1) performed a successful flyby at the asteroid in
July 1999, passing Braille on the nightside with a relative velocity of 15
kilometers [nine miles] per second and allowing, for the first time, a
direct measurement of an asteroidal magnetic field. Richter et al. ["First
direct magnetic field measurements of an asteroidal magnetic field: DS1 at
Braille"] conclude that the measured field is simply the unperturbed dipole
field of the asteroid, and estimate the upper limit of Braille's magnetic
moment to be about 2.1 X 10^11 ampere meter-squared (A-m^2).

Authors: I. Richter, K.-H. Glassmeier, F. Kuhnke, G. Musmann, C. Othmer,
Inst. for Geophysics and Meteorology, Technical U. of Braunschweig,
Braunschweig, Germany; D. E. Brinza, B. T. Tsurutani, JPL, Caltech,
Pasadena, California; M. Cassel, Inst. for computer and Communication
Network Engineering, Technical U. of Braunschweig, Braunschweig, Germany; K.
Schwingenschuh, Ins. For Space Research, Technical U. of Graz, Graz,


From Daniel Spires <>

From Yahoo News, 7 May 2001
By ANDREW BRIDGES, AP Science Writer

LOS ANGELES (AP) - A group of scientists is seeking a standardized protocol
for dealing with the possibility of an asteroid or comet striking the Earth,
saying humans can do more than the dinosaurs ever could before a colossal
impact precipitated their extinction 65 million years ago.
The call comes as interest grows in the swarm of asteroids and comets that
orbit the sun in the Earth's immediate neighborhood. The concerns were
sparked in part by several recent false alarms about impending impacts. "In
some sense, it's something we know we need to worry about, but we need to
decide at what level we need to worry about it -- and that's a question for
everybody," said Daniel D. Durda, a research scientist in the department of
space studies of the Southwest Research Institute in Boulder, Colo.

In recent weeks, a paper written by Durda and fellow scientists Clark R.
Chapman and Robert E. Gold has been making the rounds among experts who
study impact hazards. The goal, they write in the 19-page paper, is to
encourage discussion of how to replace the "haphazard and unbalanced" way
the world now addresses any potential impact.

"They are spot-on that this is a problem. They are also right on time in
terms of this just now being recognized as serious enough a topic so as to
go to the next step in terms of 'what if,'" said Richard Binzel, a professor
of planetary science at the Massachusetts Institute of Technology who
developed a scale to rank the potential danger of an impact. "We have now
overcome the giggle factor."

How serious the potential threat could be is underscored by an effort
sponsored by the National Aeronautics and Space Administration to catalog 90
percent of all near-Earth objects, or NEOs, that are 0.6 miles or larger in

The objects are a mix of comets, frozen balls of ice and dust that formed in
the far reaches of the solar system, and asteroids, which were formed in the
inner solar system between the orbits of Mars and Jupiter. Occasionally,
those objects are pushed closer to the sun, either through
collisions or by the tug of gravity, and cross the orbit of the Earth. So
far, the search effort has turned up about half of an estimated population
of 1,100 NEOs.

"It is really in the last few years the search effort has begun to bear
fruit and bear it massively," said Thomas Morgan, discipline scientist for
NASA's NEO observation program.

If an Earth-bound asteroid or comet were spotted, scientists have proposed
either attaching a rocket engine to it to nudge it out of the way, or
smashing it to pieces with an atomic bomb.

But even if a warning about a potential impact comes years or decades in
advance, the feasibility and expense of such a deterrent is unknown. If an
attempt to destroy or deflect an NEO should fail, and an object just a
half-mile in diameter struck the Earth, it would unleash an amount of energy
equivalent to 10 million times the power of the atomic bomb dropped on
Hiroshima. The event could do for many humans what a larger object is widely
believed to have done for the dinosaurs.

"The public has all heard of the extinction of the dinosaurs, and they
expect something to be done about (any potential impact), so therefore
something should be done," said Bill Cooke, a NASA contractor and space
environment expert who has penned his own paper on the subject. The Federal
Emergency Management Agency, for one, would respond in a way similar to how
it does now with hurricanes -- or the recent return to Earth of the Russian
Mir space station.

"If we were dealing with a larger object, like an asteroid that could have a
much more severe impact on the United States, as we have more advance
knowledge of where it might hit, we would immediately start alerting states
that something was coming," said Marc Wolfson, a FEMA spokesman. For now,
word of a potential threat comes by way of a casual bulletin
posted on the Internet that is invariably redistributed by the media.

"There's nothing set in stone yet as far as procedures go. That's what we
want to get people talking about: Who should be notified? Who shouldn't?
There's no desire to be secretive, but you don't want to cry wolf too
often," Durda said.

Such a cry has come once in each of the past three years, most recently in
November when astronomers announced an object known as 2000 SG344 had a
1-in-500 chance of hitting the Earth in 2030.

According to a then-new International Astronomical Union policy, astronomers
made that announcement within 72 hours of reaching a consensus that a risk
to the planet existed.

With SG344, however, the alarm was retracted almost immediately as other
astronomers better calculated the object's orbit. "It was a very normal
scientific process, but in the public's eye it looked like a mistake,"
Binzel said. "It's a trade-off between being very open and honest about what
we have and waiting and waiting until we have every last piece of data in

One expert said the flaps, while embarrassing, were an issue of public
relations, and not science. "These are problems in communication. They are
not problems in the basics of what we're doing," said David Morrison,
chairman of the International Astronomical Union's working group on NEOs.
"The issue is really one of how do we communicate with the media and the

Copyright 2001, AP

[MODERATOR'S NOTE: I apologise if readers feel a bit bored by this old
story. In fact, it is *exactly* the same story Associated Press posted
almost a month ago (15 April). Back then, it was released under the headline
"Doom's day news protocol wanted: Scientists worry about how to worry about
asteroids", see:\index\newsarchives\laxpsd\fpg\20010415\797775_isn15ast.txt&puid=1453 ].
In the meantime, an for almost
a year now, calls for effective changes to the flawed procedures for
publicly announcing an "impact threat" have been ignored. One thus has to
wonder what all this fuss is about, and why AP re-issued the same story yet
again? Let me put it this way: is this just another PR exercise, or is there
really a change of heart among those U.S. colleagues who have so far been
rather reluctant to revised the IAU protocol? BJP

Same old story also at:

From CNN, 8 May 2001

From Nando Times, 7 May 2001,1080,500558856-500798437-504292519-0,00.html   



From Michael Paine <>

Dear Benny

The following statement from CCNet 4 May doesn't show a very good
understanding of events randomly distributed in time (if impacts are indeed

"An impact this size on the Moon is predicted to happen once every
15 million years or so," Paul Withers told BBC News Online. "Having one
happen in the past 1,000 years would suggest that the predictions might
be dangerously incorrect and the Earth might be in more danger from
colliding space rocks than is currently thought."

In any, case LPL's Crater Calculator
( ) gives a predicted impactor
diameter of 850m (assuming a stony asteroid generated the 22km crater on the
Moon), not the 3km quoted in the article. Therefore the odds of such an
impact in the last 1000 years are very roughly 1 in 1000 (assuming such
Lunar impacts occur with an average interval of one million years but are
randomly distributed). Therefore a large crater that young on the Moon would
be unusual but not surprising.

Nevertheless, the evidence seems to be building up against crater Giordano
Bruno being linked to the 1178AD account.

Michael Paine


From Andy Smith <>

Hello Benny and CCNet,

It is just great to be connected to this collective brain and to be
cooperating with all of you, in meeting the most important technical
challenge in history. There are so many really outstanding contributions
coming to the Net. Many thanks to the contributors and the host.

The piece that Ed Grondine sent to the 2 May letter was excellent and we
want to express our appreciation to Ed for that and to Michael Paine, Duncan
Steel and all of our regular experts, for the work they share.

U.S. Congressional Natural Hazards Caucus

We want to encourage all to contact this group and ask that they recognize
and address the asteroid/comet danger. One of our top priority tasks is to
inform policy-makers of the NEO issues. Most are very poorly informed...and
that is a big part of the problem.

We also devote some effort to the Congressional Space Sub-Committee, which
Ed mentioned in his paper. There are still a few members on this committee
who were there and supported emergency readiness during the 1993 hearing.
Congressman Hall is a good example...a senior member and a strong supporter.

The National Space Society, Planetary Society, the AIAA and others are all
working to get support on the hill and we commend them.

Things are improving and we encourage continued efforts to inform
policy-makers, around the world. The U.K. folks did an outstanding job and
are a great model information effort.

The Super Terrestrial Asteroid Telescope (STAT)

At least one large survey instrument is a must (6 to 8 meter primary with
30k x 30k, or so, CCD). It would be nice if we had more than one of these
and a good orbiting survey system. We hope the first STAT will be sposored
by an international program. 

We are encouraging other large survey telescopes (Sloan Digital Sky Survey,
Canada/France/Hawaii, etc.) to help and we are interested in any ideas and
contacts that might be useful in this recruiting. Also, we are seeking more
NASA funding to support the great NEO hunting teams, around the world, and
the increasing number of private astronomers who are helping.

International Planetary Protection Alliance (IPPA)

We plan an IPPA meeting, at the International Space Development Conference
(ISDC2001), which will be held here in Albuquerque, later this month. The
agenda will include a discussion of ways to facilitate world-wide
communication and cooperation, on planetary protection, and ways to increase
support and funding levels. We welcome your e-mail and personal
participation in this meeting and in our Asteroid/Comet Workshops (next
para.).  If you want to make a submissions, just send us abstracts. 

Asteroid/Comet Workshops (ACW)

We now have ACW efforts planned for the International Space Development
Conference (ISDC2001), later this month; the Air Force/AIAA SPACE
2001, in August and the American Civil Engineering Society
and Robotics 2002 Conference, next March. These workshops are all aimed at
increasing the level of awareness, in the technical world and in the public

Space Shield Web Information

The information content on the Russian Space Shield Web page is growing and
there are some very interesting summaries from the SPE 2000 Conference. We
appreciate the effort which is going into this and we are also looking
forward to more detailed interception/deflection plans and studies, in the
near future.


This Italian site is doing a terrific job of presenting NEO technical detail
and it is a great companion to the MPC NEO sites. Our thanks to both groups.

The European technical community and Spaceguard are making great progress
and showing great examples of openness and international cooperation.


Andy Smith


From the Proceedings of the National Academy of Sciences of the USA, 8 May

Proc. Natl. Acad. Sci. USA, Vol. 98, Issue 10, 5393-5398, May 8, 2001

Lessons from the past: Evolutionary impacts of mass extinctions

David Jablonski*
Department of Geophysical Sciences, University of Chicago, 5734 South Ellis
Avenue, Chicago, IL 60637


Mass extinctions have played many evolutionary roles, involving differential
survivorship or selectivity of taxa and traits, the disruption or
preservation of evolutionary trends and ecosystem organization, and the
promotion of taxonomic and morphological diversificationsoften along
unexpected trajectoriesafter the destruction or marginalization of
once-dominant clades. The fossil record suggests that survivorship during
mass extinctions is not strictly random, but it often fails to coincide with
factors promoting survival during times of low extinction intensity.
Although of very serious concern, present-day extinctions have not yet
achieved the intensities seen in the Big Five mass extinctions of the
geologic past, which each removed 50% of the subset of relatively abundant
marine invertebrate genera. The best comparisons for predictive purposes
therefore will involve factors such as differential extinction intensities
among regions, clades, and functional groups, rules governing postextinction
biotic interchanges and evolutionary dynamics, and analyses of the factors
that cause taxa and evolutionary trends to continue unabated, to suffer
setbacks but resume along the same trajectory, to survive only to fall into
a marginal role or disappear ("dead clade walking"), or to undergo a burst
of diversification. These issues need to be addressed in a spatially
explicit framework, because the fossil record suggests regional differences
in postextinction diversification dynamics and biotic interchanges.
Postextinction diversifications lag far behind the initial taxonomic and
morphological impoverishment and homogenization; they do not simply reoccupy
vacated adaptive peaks, but explore opportunities as opened and constrained
by intrinsic biotic factors and the ecological and evolutionary context of
the radiation.


To the conservation biologist, there is little positive to be said about
extinction. From an evolutionary perspective, however, extinction is a
double-edged sword. By definition, extinction terminates lineages and thus
removes unique genetic variation and adaptations. But over geological time
scales, it can reshape the evolutionary landscape in more creative ways, via
the differential survivorship of lineages and the evolutionary opportunities
afforded by the demise of dominant groups and the postextinction sorting of
survivors. The interplay between the destructive and generative aspects of
extinction, and the very different time scales over which they appear to
operate, remains a crucial but poorly understood component of the
evolutionary process.

The fossil record is rich in extinction events at all intensities and
spatial scales, and thus provides the essential raw material for an
extremely important research objective: the comparative calibration of
evolutionary responses, both positive and negative, to perturbation. Despite
limits on direct comparisons to present-day and future events, discussed
below, paleontological data afford the opportunity to test the evolutionary
impact of such factors as the initial state of the system, the nature,
duration, and magnitude of the perturbation, and postextinction physical and
biotic conditions. Comparative analysis of the Big Five mass extinctions (1,
2) is just beginning, as is work on the myriad smallerand sometimes more
localizedevents manifest in the geologic record, and so this paper is as
much a research agenda as a review. One approach to the problem is through
the related issues of extinction selectivity and evolutionary continuity
across mass extinction events in the geologic past. Recent work on the
geographic fabric of extinction events and their aftermath suggests that the
spatial dimension of diversity dynamics also will be an important component
of a rigorous theory of extinction and its evolutionary consequences, and so
although data are sparse I will raise some of these issues as well.

Selectivity and Loss

Mass extinctions would be important evolutionary agents even if they simply
intensified variations in clade survivorship seen in times of low extinction
rates. For example, if mass extinctions primarily removed lineages in
decline or in the early stages of diversification, truncating the time span
available to those and other clades for the acquisition of evolutionary
novelties, then they would significantly reinforce the stability of the
status quo. The fossil record shows, however, that the major extinction
events of the geologic past have played a larger and more complex role, by
removing not just marginal players but also dominant incumbents, owing at
least in part to extinction selectivities that are partly independent of
those seen under "normal" extinction regimes. For example, factors such as
local abundance, species richness, and species-level geographic ranges, all
apparently significant during times of low extinction intensities (3),
played little role in the survival of marine invertebrate clades during the
end-Cretaceous (K-T) mass extinction, where the data are most extensive (2,
4, 5, ), and have been unimportant in at least some of the other mass
extinction events as well (2, 6). At the same time, broad geographic
distribution at the clade level, regardless of species-level ranges,
significantly enhanced survivorship at all of the major extinction events
(2, 4, 7) (note that this discordance across hierarchical levels means that
surviving clades need not consist of generalized or opportunistic species,
contrary to some oversimplifications of these results). These analyses
suggest that clades or adaptations may be lost not because they are poorly
adapted to the pre(or post) disturbance settings, but because they lack the
broad geographic deployment or other traits that favor survival during the
extinction bottlenecka pattern of "nonconstructive selectivity" (8) that
yields differential survival among clades without promoting the long-term
adaptation of the biota (2, 6, 9).

This is not to say that traits favored under low extinction intensities were
never advantageous during mass extinctions: resting stages in phytoplankton,
occupation of unperturbed habitats or regions, physiological tolerances that
happened to match the extinction-driving stresses, and perhaps particular
ecological strategies, all might play a role in survivorship (10-12).
Further, the broad correspondence between survivorship during mass
extinction and long-term clade volatility (variance in standing diversity,
i.e., net diversification rates rather than per-taxon origination or
extinction rate) (13-15) suggest that other intrinsic biotic factors (6)
carry over from low to high extinction-intensity regimes. Little has been
done to explore this possibility, however, or the alternative that taxa with
high per-taxon turnover rates have a lower threshold for crossing into the
mass-extinction selectivity regime.

Given that some clades show consistently severe or mild responses to
extinction events, which suggests that intrinsic biotic factors are
important determinants of survivorship, why does the vulnerability of other
clades appear to vary significantly among extinction events (6, 16)? This
question bears critically on the evolutionary consequences of extinction
events but has received little attention. Potential explanations range from
long-term hardening of clades by the removaland failure to
re-evolveextinction-prone constituents, to contrasting forcing mechanisms in
the different extinction events, to fortuitous trait combinations evolved
under "background" extinction regimes. Such analyses also are needed to make
better biological sense out of apparent selectivity against major clades
(e.g., ammonites, mosasaurs, dinosaurs etc. at the K-T boundary) when other
selectivities appear indifferent to clade membership [e.g., widespread vs.
restricted-range bivalves and other taxa at many extinction events (2, 4)].

I should note that the terms background and mass extinction should be used
carefully: major extinction events stand out in geologic time series as
maxima against a local background of lower rates, but the overall frequency
distribution of extinction intensities is a highly skewed, unimodal
continuum (9). Contrasts in selectivity between the major extinction events
and times of relatively low extinction suggest a threshold effect (2, 5),
but the position and taxonomic generality of that threshold is uncertain;
comparative analyses that encompass smaller extinction episodes such as the
Cenomanian-Turonian and Eocene-Oligocene events would be valuable.

The likelihood of clade- or ecosystem-specific thresholds for the onset of
mass-extinction selectivities underscores the complexity underlying
extinction time series in the fossil record, a point sometimes lost in the
general focus on a few of the most massive events. The direct comparability
of the Big Five mass extinctions to present-day biodiversity losses remains
unclear. Although present-day losses are severe and appear to be
accelerating (17), they have yet to approach the scale of the Big Five
extinctions of the geologic past. For example, the K-T extinction removed
50% of the marine bivalve genera globally (4), and 97% of the
photosymbiont-bearing coral species (and 83% of those genera) (18), and the
sampling biases inherent to the fossil record virtually require that these
victims were drawn from the more abundant and widespread components of the
biota (2, 9). Viewed in this light, these are shocking statistics that
exceed even the most severe estimates for present-day losses, although
long-term projections eventually can approach such magnitudes. Further, over
the past 2,000 yr species-poor clades and geographically restricted species
have been the overwhelming majority of losses (19), corresponding to an
intense version of the "background extinction" regime rather than the mass
extinction selectivities of the fossil record.

This is neither to belittle the violence being wrought on today's
biodiversity, nor to imply that the fossil record offers few insights
regarding the future of evolution in the face of human activities and other
stresses. It does suggest, however, that the most useful comparisons must go
beyond absolute extinction intensities to involve such factors as: relative
extinction intensities among regions, clades and functional groups;
long-term effects of geographic variation not only in extinction but also in
postextinction biotic interchanges and evolutionary dynamics; patterns of
biotic continuity, lag times, and innovation as reflected in postextinction
evolutionary rates and patterns. Also important, of course, are the looming
questions of what causes the transition to selectivities seen under
paleontological mass-extinction regimes, and whether that threshold can be
avoided in the near future. Still unknown, for example, is whether that
threshold is simply a function of the spatial scale and intensity of the
forcing perturbation, of the quality of the perturbation [see, for example,
the apparently more severe biotic effects of increased seasonality as
opposed to simple changes in mean annual temperature (20)] or whether
feedbacks involving, for example, the compounding of perturbations (21), or
the disruption of biotic interactions or community structures come into

In principle, threshold effects should be detectable in time series around
mass extinction events, and this would be especially valuable in light of
the cumulative extinction processes operating today. The demonstrable
selectivity of extinctions raises the issue of weakening vs. hardening of
the biota if unfavorable conditions are imposed over a protracted interval:
as the most vulnerable taxa such as endemic species are lost, under what
circumstances will the extinction-resistant residue withstand further
stresses, and when will they give way to the mass-extinction regime? A
hardening process may underlie the pulse of extinction near the onset of
Pleistocene glaciation and the dearth of extinction thereafter (22) (the
end-Pleistocene megafaunal extinction is probably a different issue), and we
need a better understanding of exactly what separates such events from the
major mass extinctions, and to what extent such hardening processes
undermine linear projections of present-day extinction estimates to future
losses. We can simply appeal again to the spatial scale, intensity, or
quality of the perturbation, or to the quality of the perturbation, but this
leads us back to the uncertain nature of the threshold, whether it is graded
or a step-function, and its potential variation among taxa, communities, and

Spatial Patterns

Most paleontological analyses of mass extinctions have neglected the spatial
dimension, tending to focus instead either on single stratigraphic sections
or regions, or on synoptic global databases. Both scales have been extremely
productive, but the global biota is spatially complex, with diversity
gradients and hotspots (e.g., refs. 23-26) and concomitant variation in the
generation and persistence of evolutionary novelties and higher taxa (27)
[although the relation to species-level evolutionary dynamics is still
unclear (28, 29)]. Paleontological analyses that contain a spatial
component, for example regarding regional extinction events at all scales
(30) or the biogeographic fabric of postextinction evolutionary patterns,
therefore would be especially valuable with reference to present-day and
future processes. Biotic interchanges in the paleontological record, such as
the late Cenozoic responses to the joining of North and South America after
the final uplift of the Panama Isthmus, or the opening of transpolar
interchange between Pacific and Atlantic, clearly document asymmetries in
biotic interchanges that correspond to regional differences in extinction
intensities (31, 32). These paleontological findings that regions suffering
greater losses were more heavily invaded is an important verification and
extension into deep time of observations made in modern communities (33).

Geographical analyses of mass extinctions and their aftermath, however, show
that more complex dynamics may sometimes operate. For example, although K-T
extinction intensities were statistically homogeneous for marine mollusks on
a global scale (except perhaps for shallow, clear-water tropical platforms),
the evolutionary and biogeographic response was decidedly inhomogeneous. Of
the four regions analyzed as time series (34), only the North American Gulf
and Atlantic Coastal Plain showed a prolific but short-lived burst of
diversification by several clades [termed "bloom taxa" (35)] that were
quiescent elsewhere and was significantly more subject to postextinction
biotic invasions. Although further analyses are desirable, particularly from
a phylogenetic standpoint, these patterns are likely to be robust: they hold
whether the bloom taxa are treated as a proportion of the biota or as raw
species numbers when the K-T bottleneck is taken into account (34).
Furthermore, neither burst nor excess invasion appears in an extensive new
analysis of an important fauna in the earliest Tertiary of northern Europe
(36), which is the region most likely to conform to North America by reason
of proximity and climatic similarity.

Understanding these paleontological patterns is particularly pressing in
light of the massive biotic interchanges that are currently being directly
or indirectly mediated by human activities. Why was North America subject to
more intense invasion after the K-T event despite its unexceptional (if
severe) extinction intensities? This response implies a nonlinear between
extinction and invasion intensities, or perhaps simply a threshold above
which the relation breaks down. Another possibility is that when losses
approach paleontological mass-extinction levels (that is, 50% of the
relatively abundant and widespread genera) or are globally both severe and
homogeneous, qualitative as well as quantitative losses determine the
probability of the evolutionary excursions and invasions seen in North
America: the identity of the victims and not just their numbers becomes
particularly important. The functional role of taxa lost from each of the
regional biotas will be difficult to assess rigorously, but divergent
regional responses to homogeneous extinction intensities provide a natural
experiment sufficiently rich in potential insights to demand further
investigation. Lockwood's analyses showing no relation between abundance and
survivorship in this fauna undermines one of the simplest hypotheses: that
preferential removal of abundant and thus dominant taxa was masked by a
strictly taxonomic approach (although a detailed parallel analysis of other
regions is required for a definitive test, of course).

The evolutionary effects of biotic homogenization may depend in part on how
it is achieved. Homogenization via elimination of endemics will leave a
residue of already widespread taxa that may be relatively resistant to
geographic isolation and rapid diversification, whereas homogenization via
range expansion may more readily promote the origin and diversification of
new endemic taxa. Invaders are not drawn randomly from the source biota,
however (34, 37), and this bias could itself channel subsequent evolution
into narrower pathways among regions than would otherwise be expected.

Spatial effects may be important in finer scales as well. For example, in
North America within-habitat molluscan diversity appears to recover within a
few million years after the K-T extinction (38), but total regional
diversity evidently does not reach preextinction levels until roughly 10
million years after the event (34, 35). Although this result needs to be
verified elsewhere, and tested more rigorously for sampling artifacts, it
suggests that beta diversity, the differentiation of local faunas among
habitats and along environmental gradients, takes longer to recover than
alpha, i.e., local, diversity.

Continuity and Creativity

Mass extinctions have never entirely reset the evolutionary clock: even the
huge losses at the end of the Permian, which appear to have permanently
restructured marine and terrestrial communities, left enough taxa and
functional groups standing to seed the recovery process without the origin
of new phyla (39). One key to understanding the past and future evolutionary
role of extinctions will involve the factors that permit the persistence of
certain biological trends or patternse.g., net expansion or contraction of
clades or directional shifts in morphologyin the face of extensive taxonomic
loss and ecological disruption. Besides extinction, at least four
evolutionary patterns can be seen in the fossil record. These are: (i)
unbroken continuity, (ii) continuity with setbacks, (iii) survival without
recovery ("dead clade walking"), and (v) unbridled diversification.

Unbroken Continuity. Some large-scale patterns withstood one or more of the
Big Five extinctions with little disruption. These include the continued
dominance of reefs by rugose and tabulate corals and stromatoporoid sponges
across the Ordovician-Silurian boundary (40, 41), the escalation of
morphological responses seen in molluscan shells to increased predation
intensity across the K-T boundary (42), the prolonged Paleozoic decline of
trilobites (43), and the onshore-offshore expansions and retreats of a
number of post-Paleozoic marine orders (44).

Continuity with Setbacks. Other trends suffer setbackspresumably owing to
the contrast between mass extinction and "normal" selectivitiesbut then
resume their long-term trajectories. These include rising cheilostome
bryozoan dominance relative to cyclostomes (45), the ecological expansion of
angiosperms (46, 47) although this may be more an ecological than an
evolutionary setback, and the spread to greater burrowing depths by veneroid
bivalves, all at the K-T boundary, the early Paleozoic spread of
suspension-feeding bivalves to offshore shelf environments (48), and the
overall Paleozoic increase in suture complexity in ammonoids (49). An
important open question amenable to direct testing and simulation is whether
such setbacks are generally a simple byproduct of high extinction
intensities (if the extremes of the morphospace volume are sparsely
occupied, for example, then random extinction could clear those portions),
or represent selection against the traits being maximized under low
extinction intensities.

Dead Clade Walking. Clade survival is no guarantee that preextinction trends
will persist or be reasserted in the postextinction setting. Each extinction
has examples of clades that survived the extinction event only to fall into
a marginal role or eventually disappear (dead clade walking). These include
bellerophontid snails (7) and prolecanitid ammonoids at the Permo-Triassic
boundary (50), the brachiopod order Spiriferoida after the end-Triassic
extinction (51), and the planktic foraminiferal Zeauvigerina lineage after
the K-T event (52). Such lingering demises need to be tested against
stochastic attrition, of course (43). My preliminary, unpublished analysis
suggests that the intervals after mass extinctions tend to be significantly
enriched in taxa that failed to cross the next stage boundary, relative to
other intervals before the extinction event; in other words more clades that
survived a mass extinction tend to dwindle or disappear shortly after the
event than would be expected by chance. Also intriguing is the geographic
variation in the proportion of dead clade walking taxa across the K-T
boundary, with values highest not in North America (which makes an
interesting statement on the impact of the greater influx of invaders
therethey followed extinctions but did not drive them), but in the tropical
Indian Ocean.

These diverse postextinction trajectories again demonstrate that analysis of
the evolutionary role of extinctions must include much more than taxonomic
survivorship at the event itself. We need to understand why some clades, and
some polyphyletic trends such as escalation of antipredatory defenses,
persist uninterrupted across the extinction event, why others stumble but
recover their preextinction trajectory, and still others survive but never
recover. All of the patterns discussed so far strongly attest that
postextinction evolutionary processes involve not simply unbridled radiation
(see below), but a sorting of survivors in the postextinction world. At this
early stage, many alternative hypotheses are feasible and the relative power
of the alternatives may vary among different situations. The most obvious is
the taxonomic breadth of the trend: all else being equal, any evolutionary
trend that advances along a broad ecological or taxonomic front is less
likely to be halted by extinction. Although this is surely a factor, it is
unlikely to be sufficient in all cases, because many trends are fairly
circumscribed phylogenetically, as in the bryozoan and veneroid examples
given above.

Given the discordance in selectivity between times of high and low
extinction intensities, another factor in the persistence of trends is
likely to be the strength of association between traits involved in trends
and those related to survivorship. The role of this macroevolutionary
linkage in promoting the long-term persistence of trends is virtually
unexplored. A final potential explanation is even more context-specific,
that the differential persistence of trends depends less on the intrinsic
traits of clades than on the strong variation recorded in postextinction
recovery (i) among ecosystems, e.g., the more rapid recovery of diversity in
oceanic plankton vs. marine benthos (53, 54) (with potentially important
implications for the relative persistence of mineral and nutrient cycles);
(ii) across ecological scales, e.g., discordances in the time to recovery of
local vs. global diversity (as mentioned above, with potentially important
implications for the accumulation of biological diversity and the
development of spatial structure); and (iii) among regions in clade dynamics
and biotic interchanges, e.g., the concentration of bloom taxa and
postextinction invasions in particular areas (with potentially important
implications for the persistence and recovery of local biotas and
intrerregional source-sink dynamics).

Unbridled Diversification. The most dramatic and creative evolutionary role
of mass extinctions is the promotion of postextinction diversifications,
typified most vividly by the exuberant radiation of the mammals after the
demise of the dinosaurs and other reptilian clades at or near the K-T
boundary. Postextinction bursts of diversification have been extensively
discussed and documented for many extinction events, both morphologically
and at several taxonomic levels (6, 39, 41, 55-58). Therefore, before
returning to the need for further analysis of geographic variation in
evolutionary dynamics, I will make only two further points, on
predictability and time scales.

Predictability. Although the evolutionary response to mass extinction has
sometimes been depicted simply in terms of the reoccupation of preextinction
adaptive peaks ("reinventing the ecological wheel," ref. 59), evolution is
both too opportunistic and too constrained by inherited body plans for this
to be wholly true. Striking convergences in form and habit are, of course, a
major theme in evolution, but postextinction dynamics are complicated by
near-simultaneous radiation of multiple clades [with the powerful incumbency
advantage at stake (32)], the distinct ecological context of each
postextinction interval, and the raw material provided by surviving
lineages. These effects can be seen in the incomplete congruence of
successive occupations of morphospace after extinction events (60, 61).

To drive home these important but somewhat abstract points on the long-term
prospects for evolutionary replacements, consider the Cenozoic history of
birds. The large, flightless phorusrhacid and diatrymid birds, probably the
top carnivores of early Cenozoic terrestrial communities (62, 63),
interfered with the triumphant mammalian ascent to center stage in the
postdinosaurian world, and probably were not replaced by an exact mammalian
analog once they disappeared. Note also that these carnivorous birds
opportunistically converged on theropod dinosaurs rather than adhering to
the pterosaur models that might have been the most likely targets for
convergence given a flying avian starting point (62). Over the course of
Cenozoic diversification, other birds did assume modes of life similar to
those vacated by pterosaurs: skimmers may roughly correspond to
Tropeognathus with its keeled jaws, swallows and swifts to Pterodactylus
with its similar size and wing proportions, flamingos to Pterodaustro with
its bristling array of fringe-like teeth, and perhaps even condors to the
enormous Quetzlcoatlus (64, 65). This does not mean, however, that birdsor
even birds plus batsmanaged to occupy the full range of pterosaur habits
(66). Equally important, the granivorous habit so important in modern birds
evidently represents a novel expansion of bird ecospace relative to their
supposed pterosaur models (see ref. 66 on the avian trophic
diversification). There may be good functional or ecological reasons for
this (e.g., was the Mesozoic seed bank as rich and dependable a resource as
in the angiosperm-dominated Cenozoic?), just as there seems to have been for
the absence of baleen-like filter-feeding in Mesozoic marine reptiles (67),
but such constraints and contingencies are precisely the factors that
prevent a given set of clades at a given time from fully overlapping the
evolutionary pathways of their predecessors. Attempts to predict
evolutionary behavior after major extinction events can only operate in
broad generalities, and always with the caveat, "expect the unexpected."

Time Scales. The fossil record shows that destructive and generative aspects
of extinction generally operate in different time frames, as many authors
have pointed out (2, 41, 68). The biotic impoverishment and homogenization
necessarily precedes the evolutionary response, and there is surprisingly
little hard evidence for major evolutionary innovations within a major
extinction episode. Even for apparently protracted or multistep extinctions
that see origination within the extinction interval, such as the
end-Ordovician or end-Permian episodes, "little biological innovation is
apparent" (41).

Recoveries of different biomes, clades, or communities may have different
postextinction lag times; for example, broadly defined "reef" systems lag
behind oceanic plankton systems (see ref. 2 for discussion). Whether these
lags reflect a general property of large-scale diversity dynamics (13, 69),
sampling and other biases (6, 70), the duration or intensity of
environmental stresses (71), a protracted process of assembling new
ecological communities (2, 72), or evolutionary waiting times set by
intrinsic diversification rates (73) awaits further comparative analysis.

Geography. The spatial dimension is important not only to extinction
selectivity and postextinction interchange, but to long-term evolutionary
dynamics in a postextinction world. Certain habitats and regions, such as
onshore marine settings (44), and the tropics in both marine (27) and
terrestrial (74-76) settings, appear to be important sources of
postextinction evolutionary novelty, but the implications of this nonrandom
creativity have only begun to be explored. On finer geographic scales, a
systematic search for diversity hotspots in the geologic record to test for
their long-term persistence and evolutionary significance would be valuable.
For example, is the end-Ordovician extinction of brachiopods and other
benthic taxa in North America a potential case study in the destruction and
later refurbishment of a diversity hotspot? North America straddled the
equator and harbored a rich biota of endemic taxa in the epicontinental sea
that occupied the center of the continent. Oscillating climates and
fluctuating sea levels virtually eliminated this and other interior seaways
and their biotas, and the postextinction interval saw an invasion pulse as
taxa from outside the region expanded to occupy the returning favorable
habitats (77, 78).

Tracking such hotspots and other crucibles of biotic novelty over
evolutionary time might help to prioritize targets for both research and
conservation efforts in the near future. Do relatively localized hotspots
primarily contribute taxonomic richness to the global biotic inventory, or
are they also important reservoirs of biodisparity, that is morphological
richness? The evolutionary importance of the answer will depend in part on
the mean lifetime of such hotspots, and the extent to which novelties that
arise in hotspots tend to spread elsewhere, as has been documented for
novelties that originated in onshore environments or within tropical
latitudes (27, 44, 74-76). For these and many other questions, paleontology
can be a rich source of natural experiments in macroevolutionary dynamics
before, during, and after perturbations of widely varying intensities and


I would not go far wrong in saying that the most dramatic evolutionary
effects of mass extinctions can be epitomized in just four words: they
remove successful incumbents. But going beyond what amounts to a concession
to contingency, what are the lessons of the past that transcend the specific
mechanisms, intensities, and participants of earlier events?

(i) Mass extinctions happen. The fossil record provides ample evidence that
even the more widespread and species-rich clades, ecosystems, and
biogeographic provinces are not infinitely resilient. Biogeochemical and
other data are accumulating on the concomitant breakdown of nutrient cycling
and other ecosystem-level processes (53), and the links among the collapse
and recovery of taxonomic diversity, morphological, or functional disparity
and ecosystem function should be a high priority.

(ii) Survivorship during mass extinctions need not be closely related to
many aspects of biological success as measured during "background" times. An
understanding of the evolutionary role of mass extinctions requires
continued analysis of why well-established incumbents are lost, surely at
least in part a function of the spatial scale of perturbations, and the
long-term consequences of such losses.

(iii) Extinction itself promotes biotic interchange. Asymmetries in ancient
biotic interchange generally appear to reflect geographic differences in
extinction intensity. The K-T extinction shows, however, that although
biotic interchanges pervade the postextinction world, simple linear
relationships can break down to produce unexpected source-sink patterns.

(iv) The evolutionary response to mass extinction is slow on human time
scales, difficult to predict owing to the contingencies of postextinction
conditions including the identity and evolutionary dynamics of the
survivors, and geographically heterogeneous. Each of these complications,
however, is amenable to comparative paleontological analysis and modeling,
with the attendant opportunities for detecting patterns, testing hypotheses,
and drawing lessons relevant to the future of evolution.


I thank D. H. Erwin, S. M. Kidwell, A. H. Knoll, R. Lockwood, and D. M. Raup
for valuable discussions and reviews, N. Myers and A. H. Knoll for the
invitation to participate in such a stimulating interdisciplinary symposium,
and the National Science Foundation and the John Simon Guggenheim Memorial
Foundation for support.


K-T, end-Cretaceous.

* E-mail:

This paper was presented at the National Academy of Sciences colloquium,
"The Future of Evolution," held March 16-20, 2000, at the Arnold and Mabel
Beckman Center in Irvine, CA.

Lockwood, R. (1997) Geol. Soc. Am. Abstr. Programs 29, A-404.
Lockwood, R. (1998) Geol. Soc. Am. Abstr. Programs 30, A-286.


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Copyright 2001 by the National Academy of Sciences


From SpaceDaily, 8 May 2001

by Paul Kimpel

Gainesville - May 8, 2001
In what reads like a story from a 1950s science fiction magazine, a team of
University of Florida scientists has genetically modified a tiny plant to
send reports back from Mars in a most unworldly way: by emitting an eerie,
fluorescent glow. If all goes as planned, 10 varieties of the plant could be
on their way to the Red Planet as part of a $300 million mission scheduled
for 2007.

The plant experiment, which is funded by $290,000 from NASA's Human
Exploration and Development in Space program, may be a first step toward
making Mars habitable for humans, said Rob Ferl, assistant director of the
Biotechnology Program at UF.

Ferl and a team of molecular biologists chose as their subject the
Arabidopsis mustard plant. They picked it, Ferl said, because of three
attributes that make it ideally suited for the Mars mission: Its maximum
height is 8 inches, its life cycle is only one month and its entire genome
has been mapped. Moreover, in December 2000 it became the first plant to
have its genetic sequence completed.

To create the glow, the team will insert "reporter genes" into varieties of
the plant, which will express themselves by emitting a green glow under
adverse conditions on Mars. Each reporter gene will react to an
environmental stressor such as drought, disease or temperature. For example,
one version will glow an incandescent green if it detects an excess of heavy
metals in the Martian soil; another will turn blue in the presence of

In fact, one of the reporter genes itself is somewhat otherwordly, having
come from the depths of the ocean.

"What makes the plants glow blue is a protein derived from an incandescent
jellyfish whose DNA is spliced into the mustard plant," Ferl said. "The
implanted DNA then synthesizes the iridescent blue protein in the plant,
which expresses itself under stress."

Ferl's team, in collaboration with Andrew Schuerger, a manager of Mars
projects at the Kennedy Space Center-based Dynamac Corp., is competing with
other biologists to receive the NASA contract for the Mars trip.

But both men, who also are professors at UF's Institute of Food and
Agricultural Sciences, have worked with NASA before. In 1999, Ferl sent 40
reporter-gene plants into orbit aboard the space shuttle. On that flight,
gravity had an adverse effect on the plants' ability to utilize water, a
condition called "space adaptation syndrome."

The scientists are using that experience to engineer smarter plants.

"Just like humans, plants must learn how to adapt to a new environment,"
Ferl said. "We are using genetics to create plants that have the ability to
give us data we can use to help them survive."

The 2 1/2-year Mars mission -- nine months traveling 286 million miles each
way and one year stationed on the planet -- would work like this: The seeds
of the plant would make the trip aboard a spacecraft similar to NASA's Mars
Odyssey, which was launched April 7.

Upon arrival, the landing vehicle's robot would scoop up a portion of
Martian soil, and the scientists will analyze it using the robot and a
specialized camera. After modifying the soil with fertilizers, buffers and
nutrients, the scientists will germinate the seeds and grow the plants in a
miniature greenhouse on the landing vehicle.

Despite working with alien soil they know little about, the biologists are
optimistic about the experiment.

"I'm confident we can grow plants if we know the pH levels and the oxidizing
agents in the Martian soil," Schuerger said. "We'll test the soil before
planting, and then we can raise or lower pH, flush excess salts and add
nutrients as needed."

As for long-term plans, Ferl and Schuerger have worked together on a concept
called "terra-forming" or "ecosynthesis," which would use plants to reduce
the carbon dioxide in the Martian atmosphere and produce oxygen for life
processes. Although the plants are genetically engineered to detect -- and
then adapt to -- certain environmental stressors, terra- forming presents
additional obstacles.

Schuerger said that on Mars, daily temperatures range from a high of 45
degrees Fahrenheit at noon to a low of minus 170 degrees at night. Also, the
planet's moisture content is 0.3 percent, which is extremely low.

But Ferl, Schuerger and the rest of the team are taking all bettors.

"I have no doubt that we can get plants to survive on Mars," Ferl said.
"When we do, we will have shown that Earth-evolved life is capable of
thriving in distant worlds, and we will have set the stage for human

Copyright 2001, SpaceDaily

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