Transcript once-a-century atmospheric explosion (30-40 m body)

http://www.boulder.swri.edu/clark/clark.html
NEO IMPACT SCENARIOS
Clark R. Chapman
Southwest Research Institute
Boulder, Colorado, USA,
and “The B612 Foundation”
Session 3-PD-3 “Threats & Consequences II”
AIAA-2004-1416
2004 Planetary Defense Conference:
Protecting Earth from Asteroids
Garden Grove CA USA 23 February 2004
In the Post 9/11 World...
What kinds of impact
predictions do we
really have to plan for?
How does society respond to real (or imagined)
threats? It’s more than engineering, folks!
How Often Impacts
of Different Energies Happen
Asteroid Size Distribution:
Courtesy
Al Harris
Sizes, Impact Frequencies of
NEOs
Smallest, most
frequent
Leonid meteor
shower
Peekskill meteorite
Huge,
extremely rare
Tunguska, 1908
K-T mass extinctor, 65 Myr ago
SL9
hits
Jupiter
1994
Max
Nominal
Min
Asteroid Diameter (km)
Worldwide Deaths (Annual)
Worldwide Deaths (Annual)
Death Threat from Impacts, by Asteroid
Diameter and Location of Impact
(For nominal case)
Global
Land
Tsunami
Asteroid Diameter (km)
 Statistical mortality from impacts, post-Spaceguard, distinguished by size
and location of impact (NEO Science Definition Team [SDT], 2003)

SDT tsunami hazard is divided by 10 (think deaths, not property damage)

Land impacts by <100m asteroids (Tunguskas) are objectively important, but
they also occur MUCH more frequently than Global destroyers

Tunguskas and their smaller cousins may dominate popular interest in the
impact hazard, and hence the work of the NEO community.
The Four DEFT Scenarios:
Other Considerations
Remember:
an impact scenario is
unprecedented in
historical times; there
are no protocols to deal
with one, nor is there a
base of experience with
an impact’s unique
social and physical
repercussions…
 Aramis best simulates ever-changing (generally
improving) knowledge of impactor and impact
circumstances. Other cases would be similar.
 Who will inform what officials about these threats?
 Technical and political arguments in a context of
worldwide anxiety and fear.
 Preparation for evacuation, storing food, post-
disaster relief (if deflection is uncertain or fails).
Impacts of Practical Concern
OBJECT IMPACT
DIAM.
ENERGY
>3 km
1.5 mil. MT
>1 km
80,000 MT
>300 m
2,000 MT
>100 m
80 MT
>30 m
2 MT
>10 m
100 kT
>3 m
2 kT
CHANCE CHARACTER OF DAMAGE
PER 100 YR
1 in 50,000
Global climate disaster, most
killed, civilization destroyed
0.02%
Devastation of large region or
an entire ocean rim
0.2%
5 km crater; huge tsunami or
destruction of small nation
1%
Exceeds greatest H-bomb; 1
km crater; locally devastating
40%
Stratospheric explosion;
damage within tens of km
6 per century Broken windows, little serious
damage on ground
2 per year
Blinding flash, could be
mistaken for atomic bomb
Case Studies of Potential Impact
Disasters (in my 2003 OECD study)
a. Civilization destroyer: 2-3 km asteroid
or comet impact
Six case studies,
exemplifying the different
sizes and types of impact
disasters, were discussed
in these terms:
 Nature of Devastation.
 Probability of Happening,
in 21st century.
 Warning Time.
 Possibilities for Post-
Warning Mitigation.
 After-Event Disaster
Management.
 Advance Preparation.
What can we do now?
b. Tsunami-generator: ~200 m asteroid
impacts in the ocean
c. ~200 m asteroid strikes land
d. Mini-Tunguska: once-a-century
atmospheric explosion (30-40 m body)
e. Annual multi-kiloton blinding flash in
the sky (4 m body)
f.
Prediction (or media report) of nearterm impact possibility
We just experienced Case (f)
threatening a Case (d)
LAST MONTH!
d. “Mini-Tunguska”: Once-in-aCentury Atmospheric Explosion
 Nature of Devastation.
30-40 m “office building” rock hits at
100 times speed of jetliner, explodes ~15 km up with energy of 100 Hiroshima A-bombs. Weak structures damaged/destroyed by hurricane-force
winds out to 15 km. If over land, dozens or hundreds may die, especially
in poor, densely populated areas (minimal damage in desolate places).
 Probability of Happening.
Once-a-century, but most likely over an
ocean or sparsely-populated area.
 Warning Time.
Very unlikely to
be seen beforehand; no warning at all.
 Mitigation Issues.
MiniTunguska
Little can
be done in advance (an adequate
search system would be very costly).
Rescue and recovery would resemble responses to a “normal” civil
disaster. No on-the-ground advance preparation makes sense, except
public education about this possibility.
f. Prediction (or Media Report)
of Near-Term Impact Possibility
 Nature of the Problem.
Mistaken or
exaggerated media report (concerning a nearmiss, a near-term “predicted” impact, etc.)
causes panic, demands for official “action”.
 Probability of Happening.
Has
already happened several times, certain to
happen again in next decade. Most
likely route for the impact hazard to become
the urgent concern of public officials.
 Warning Time.
Page-one stories
develop in hours; officials totally surprised.
 Mitigation Issues.
Public education, at all
levels of society: in science, critical thinking, and about
risk, in particular. Science education and journalism
need improvement with high priority.
The Impact that Didn’t Happen:
AL00667, 13/14 January 2004
 Nominal MPC Confirmation Page ephemeris, based on 4 LINEAR
positions, suggests impact in 24 hr (few hrs after Bush space speech)
 Posting noticed by amateur astronomers, discussed on Yahoo’s MPML
while MPC staff, professional astronomers “in the dark”
 Cloudy skies in much of Europe and USA prevent definite follow-up
 Steve Chesley (JPL NEO Program Office) calculates 10% - 25% chance
of impact, in northern hemisphere, during next few days of ~30 m body
 Midnight considerations to announce Torino Scale = 3 prediction
 Lucky ad hoc e-mail connection enables amateur astronomer Brian
Warner, with 20-inch telescope, to search for “virtual impactors”
 Warner finds no object; LINEAR recovers object; calculations few hrs
before Bush speech place it 10 times farther away, impact ruled out
 Czech recovery next night provides designation 2004 AS1
LINEAR site in N.Mex.
Attributes of the AL00667 Case
 Predicting imminent, “final plunge” impacts is not in the
scope of the Spaceguard Survey (LINEAR, MPC, JPL NEO
Program Office, NEODys, IAU WGNEO, etc.)
The NEO Confirmation Page
 A system that notifies observers to “confirm” very preliminary
NEOs necessarily makes the data public; and if data indicate
a possible impact, they cannot be ignored
 AL00667 positions had larger-than-usual uncertainties (we
now know); but analysis of trajectories within usual
uncertain-ties yielded 40% impacting the Earth; there was no
mistake
Brian Marsden
Palmer Divide Observatory
 But AL00667 data were delayed or held private; not available
at all to experts, e.g. at Lowell Observatory, Univ. of Pisa
 Is a public announcement ethically required if there is a
professional calculation of >10% impact chance?
 Should Bayesian statistics be folded into calculation?
 Communications network for AL00667 was mainly ad hoc,
unfunded, and cannot be relied on in future
 There have been only rudimentary (at best!) protocols, plans
to handle out-of-scope, unexpected cases
Suggestions and Recommendations
in Aftermath of AL00667
 Should Spaceguard infrastructure be enhanced
to operate “24/7” and handle imminent impacts?
NO: mismatched priorities; only few-% chance
that next small impactor will be seen before it hits
 YES: only if “SDT Report” is implemented with
system optimized to find smaller impactors

“SDT Report”
August 22, 2003
 Should there be plans/protocols for best-effort
handling of unexpected, out-of-scope cases?

YES: public expects responsible, professional
responses; we were lucky this time
 Instead of “one-night-stand” preliminary data
being held private by LINEAR/MPC, should data
be made immediately available to qualified
international asteroid orbit specialists?


MPC says “NO”: unverified data can be misused
I say “YES”: preliminary, time-urgent, noisy data
are normal in science; independent calculations
are essence of open science. Why keep private?
NEO Impact Scenarios: Public
Issues
 Whether people actually “panic”, impact
predictions generate anxiety and demands
for action, for which no plans exist
 The Torino Scale provides just a first cut
estimate of how serious a prediction is
(but remember Homeland Security scale!)
 Public relations issues will evolve as
technical knowledge about impactor, time,
location of impact evolves
 “Trustworthy” handling of deflection
 Many unprecedented issues involving
evacuation, contingencies, disaster relief
 National, international responsibilities?
Public Perception
 While “known” to many from movies and the news, a
serious impact disaster has never been experienced in
recorded history.
 The tiny chances and huge consequences are
extremely difficult for people to relate to.
 The impact hazard is “dreadful” (fatal, uncontrollable,
involuntary, catastrophic, increasing…) and apocalyptic
(with religious or superstitious implications for many).
Public response to a real impending impact is
expected to be exaggerated (e.g. Skylab falling).
 Experience with news media hype and misinformation
suggests we need more science literacy among
journalists and citizens in general.
Two-Tiered Approach to Dealing
with Irrational Risk Responses
 Public officials must be prepared to
deal with disproportionate responses
The public politically demands that they do
 There are real psychological, economic, and
other consequences

 Politicians, educators, and science
journalists must endeavor to teach
citizens how to evaluate more
rationally the risks that affect them
Generally, fear would be reduced; rational
concern would lead to constructive response
 Our national and personal resources would
be employed more cost-effectively

Conclusions…
 Scenarios should extend
beyond the scientific
discovery and
reporting…and beyond
engineering considerations
of deflection…
B612
 Scenarios should also
consider the psychological,
sociological, and political
consequences of predicted
asteroid impacts and
subsequent courses of
action.