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Lifeboat Foundation
AsteroidShield
By
Al Globus and other members of
the Lifeboat Foundation Scientific Advisory Board.
Print report!
Artwork by
Don Davis of large asteroid beginning the destruction
of
most
life on Earth. Courtesy, NASA.
1. OVERVIEW
Until fairly recently there were no significant efforts to identify
asteroids and comets that may impact the Earth. This began to change
in 1992 with the
Spaceguard Survey Report which in 1994 led the House Committee on
Science and Technology to direct NASA to
work with the space agencies of other countries to identify and
catalogue within 10 years the orbital characteristics of 90% of all
comets and asteroids larger than 1 km and in orbits that cross the
orbit of Earth. In 2005, the U.S. Congress further
tasked NASA to identify 90% of near-Earth
objects with a size greater than 140 meters in diameter by the year
2020 and 90% of objects greater than 1 kilometer by the year
2008.
This report will conclude with our solutions to the problem of asteroid
impacts.
2. PROBLEM
If we don't do something, sooner or later Earth will be hit by an
asteroid large enough to kill all or most of us. That includes the
plants and animals, not just people. Maybe this won't happen for
millions of years. Maybe in 15 minutes. We don't know. For example, on
23 March 1989 asteroid 1989FC with the potential impact energy of over
1,000 megatons (roughly the equivalent a thousand of the most powerful
nuclear bombs) missed Earth by about six hours
[1]. We
first saw this fellow after closest approach. If 1989FC had come in six
hours later most of us would have been killed with zero
warning.
It's unlikely, but a large comet or asteroid could impact the Earth in
15 minutes and eventually we will be be hit, for sure. We are hit by
thousands of smaller asteroids every year and we don't see any of them
before the collision. Detection of larger, Earth-threatening rocks is
very far from complete.
At the present rate it will take
years before
we find just 90% of them. Beside these inevitable cosmic disasters the
long list of potential human-induced potential calamities —
nuclear
war, ecological collapse, global warming, epidemics, etc. — are
less
certain and far less dangerous, although much more likely in the near
term. After all, the worst of these would probably kill less than three
quarters of the people on the planet. A good sized asteroid will get us
all.
2.1 HIROSHIMA LEVEL IMPACT
We have been warned. In October of 1990 a very small asteroid struck
the Pacific Ocean with a blast about the size of the first atomic bomb;
the one that leveled Hiroshima, Japan killing roughly 200,000 people in
seconds. If this asteroid had arrived ten hours later it would have
struck in the middle of more than a million U.S. and Iraqi soldiers
preparing for war. It could have struck near U.S. forces.
The U.S.
would have thought Iraq attacked with a nuclear weapon. America would
have used its immense nuclear arsenal to turn Iraq into a radioactive
wasteland, and even one nuclear bomb can ruin your whole day. Don't
worry though, these small asteroid strikes only happen about once a
month [3]. Besides, it gets
worse.
2.2 HYDROGEN BOMB LEVEL IMPACT
Some of the 60 million flattened trees from the 1908
Tunguska event.
|
The energy of the Tunguska asteroid impact would have been
equivalent
to 10
to 40 Megatons of TNT. Had this happened over a
populated area it would constitute one of the greatest natural
disasters of all time. |
In 1908 a small asteroid (perhaps 50 meters across) hit Tunguska,
Siberia and flattened 60 million trees. That asteroid was so small it
never even hit the ground, just exploded in mid-air. If it had arrived
four hours and fifty-two minutes later it could have hit St. Petersburg
[3]. At the time St. Petersburg was the capital of Russia
with a population of a few hundred thousand. The city would have ceased
to exist. As it was, dust from the blast lit up the skies of Europe for
days.
Asteroid strikes this size probably happen about
once every
hundred years. However, this is just an average. Just because we got
hit once doesn't mean we're safe for another hundred years. Indeed,
there was another Tunguska-class strike in the Brazilian rain forest on
13 August 1930 [3]. But don't worry,
it gets
worse.
2.3 GREATER THAN EARTH'S ENTIRE ATOMIC ARSENAL LEVEL
IMPACT
It's not just Earth. In 1178 our Moon was hit by an asteroid
creating 120,000 megatons explosion (about six times the force of
Earth's entire atomic arsenal). The collision dug a 20 km (12 mile)
crater. This strike was recorded by a monk in Canterbury, England. We
are extremely lucky it didn't hit us. The moon is a smaller target and
has much less gravity to attract an impactor. If a 120,000 megaton
blast had hit the Earth our history would have been dramatically
different.
Catastrophes of this magnitude happen on Earth
perhaps once
every 1,000 years or so. We're just lucky the last one hit the Moon
instead.
2.4 FIFTY TIMES THE EARTH'S ENTIRE ATOMIC
ARSENAL LEVEL IMPACT: A BILLION DEAD
There are about 1,000 asteroids a kilometer or more in size that cross
Earth's orbit (the path Earth takes around the Sun). About a third of
these will eventually hit Earth [2]
if we don't do something
about it. An asteroid strike this large can be reasonably expected to
kill a billion people or so, depending on where it hits. A strike in
China or India will kill more, in Antarctica less. Even a strike in the
ocean would create a tsunami so enormous most people living near the
coast would be drowned.
A strike of this size is expected
about once
every 300,000 years or so. We might as well be playing Russian
roulette. Admittedly, the revolver has 300,000 cylinders, but if we
keep pulling the trigger long enough we'll blow our head off, and
there's no guarantee it won't be the next pull. But
don't worry, it gets worse.
2.5 TEN THOUSAND TIMES THE EARTH'S ENTIRE ATOMIC
ARSENAL LEVEL IMPACT BUT HIT JUPITER
INSTEAD...
|
Brown spots mark the places where fragments of Comet
Shoemaker-Levy 9 tore through Jupiter's atmosphere in July 1994.
|
The most recent large strike also missed Earth. In July 1994, the comet
Shoemaker-Levy 9 plowed into Jupiter. The comet broke up into roughly
20 large pieces before contact, but when the pieces hit they left a
string of enormous explosions clearly visible to our telescopes. The
scale of the destruction was staggering. Each impact was the equivalent
of about 10 million megatons of TNT.
If Shoemaker-Levy
had hit Earth
instead of Jupiter, in the extremely unlikely event you were alive you
certainly wouldn't be reading this report. You'd spend every waking
moment trying to survive. But don't worry, it gets worse.
2.6
TEN THOUSAND TIMES THE EARTH'S ENTIRE ATOMIC
ARSENAL LEVEL IMPACT AND IT HIT US!
Life 65 million years ago was about to
change.
Sixty-five million years ago a huge asteroid several kilometers across
slammed into the Yucatan Peninsula in Mexico. The explosion was the
equivalent of about 200 million megatons of dynamite, about the
equivalent of all 20 pieces of Shoemaker-Levy. The blast turned the air
around it into plasma — a material so hot electrons are ripped from
the
atomic nucleus and molecules cannot exist. This is the stuff the Sun is
made of. Enormous quantities of red-hot materials were thrown into
space, most of which rained down worldwide burning literally the entire
planet to a crisp. Anything not underground or underwater was
killed.
Evidence gathered by the University of Colorado at Boulder suggests
that all the dinosaurs above ground were incinerated in a few hours
reference. Surprisingly, only about 75% of the plant and animal species
on Earth were exterminated. What's surprising is that everything wasn't
wiped out. This scenario has been repeated over and over, perhaps once
every 100 million years or so. Each collision killed up to 95% of all
species on Earth. As many as two-thirds of all species that ever
existed may have been terminated by asteroids hitting the
Earth.
2.7 OCEAN IMPACT
Just because an asteroid misses land does not mean it
won't be deadly.
Courtesy, Twentieth Century
Fox from the movie
The Day After Tommorrow.
|
We know about the asteroid that killed the dinosaurs because we found
the crater. But what happens when an asteroid hits the ocean? After
all, oceans cover two-thirds of the Earth's surface. Most asteroid
strikes must be in water. Unless the asteroid is very large there won't
be a crater. However, if you drop a rock into a lake it makes a wave.
The larger the rock the bigger the wave.
Drop a 400 meter
(three
football fields) diameter asteroid into the Atlantic Ocean and you get
a tsunami 60 meters (yards) high [4]. Do that
today and beach side property values will plummet due to the sudden and
complete absence of any people or buildings. Almost every human culture
has a flood story (for example, Noah's Ark). These may be the living
memory of asteroids hitting the oceans. This is not idle speculation,
there are several hundred thousand asteroids in near Earth orbits large
enough to cause world-wide casualties by creating tsunamis [1].
Of course, if the asteroid is big enough, even a hit in the ocean will
rearrange the Earth's crust. Researchers from the University of Toronto
and the Geological Survey of Canada determined that an asteroid the
size of Mt. Everest probably hit the Earth about 1.8 billion years ago,
and literally turned part of the Earth inside out
[5]. The crater is
about 250 kilometers (156 miles) wide. It's amazing that anything
survived at all, but somehow a few of our single-celled ancestors lived
through the ensuing hell. Life started on Earth over 3 billion years
ago, but no large animals appeared until about 700 million years ago
—
perhaps because of the devastating bombardment Earth was still
suffering through.
2.8 PROBLEM SUMMARY
These are just a small sampling of the cosmic threats to Earth. We are
living in an orbital shooting gallery. There are lot of objects out
there and, someday, many of them are going to hit something — the
Sun,
another planet, or Earth (some will also be ejected from the solar
system). Of the known near earth asteroids, between 25 and 875 large
objects will hit the Earth causing global devastation and another 400
to 6250 smaller objects will strike the Earth's oceans causing tsunamis
devastating coastal regions
[4].
We just
don't know when. We don't know if the next strike will be in five
minutes or 50 million years, but we do know it will happen. It's just a
matter of time. Only mankind can end this threat. If we don't do it, no
one else will. No one else can. Fortunately, we are starting to pay
attention.
The first step is to simply find the dangerous asteroids and comets.
NASA has a program to locate potential Earth killing asteroids —
those more than a kilometer (a bit more than half a mile) across and
hopes to identify 90% of them by 2008
[6]. If one
of the unfound has our number on it, it's not only Houston that will
have a problem.
Even an asteroid only a couple hundred
meters (yards)
across may, if it hit the Atlantic Ocean, create a wave that would
completely wash over Florida, making it irrelevant in the next
Presidential election. In 2005, Congress also assigned NASA the task
of
detecting 90% of near-Earth
objects with a size greater than 140 meters in diameter by the year
2020
[7].
|
Apophis Path of Risk (PoR); the locus of points on the Earth's surface
where Apophis could
impact, if it were to impact the planet on April 13, 2036. Note that
the PoR extends almost 270 degrees
around the Earth's surface. |
We have found hundreds of kilometer-sized Earth orbit-crossing
asteroids and determined their orbits well enough to know that these,
at least, pose no threat in the immediate future, although one does
have a small chance of getting us in 2036. If we took this particular
threat seriously, we would have time to divert it. In principle, such
an asteroid can be given just a little shove and will then miss Earth.
While we're not sure of the best way to do this, if we knew a collision
was coming one can be confident that every scientist and engineer on
the planet would be bent to the task. Funding would not be a
problem.
3. SOLUTIONS
The goal is to first detect the asteroid and then to alter its
orbit [9].
If you attempt to destroy an asteroid as
they often do in Hollywood movies, you will likely change
the situation from a single impact situation to a
many impact situation.
There are many proposed methods under consideration for detecting
asteroids and altering their orbits.
3.1 DETECTION
We support our Scientific Advisory Board member Nick Kaiser's efforts to locate
any asteroids
that may impact the Earth. He is principal investigator of the $50
million Panoramic Survey
Telescope & Rapid Response System (Pan-STARRS) asteroid
early-warning system.
|
The under construction PS1 telescope, part of the
Pan-STARRS
asteroid early-warning system |
|
Schematic diagrams of the 1.4 gigapixel camera to be
installed in PS1 in mid 2007. Each of the 60 black squares in the
center of the camera is an Orthogonal Transfer Array (OTA) consisting
of
64 individual 600 x 600 CCD devices. |
Currently, it is difficult to detect asteroids approaching on the
"blind spot" caused by the glare of our sun, and this limitation can
best be solved by the creation of extraterrestrial telescopes
sufficiently removed from Earth to change their vantage point
[10].
(Asteroids are relatively small and dark so you want as clear of a view
as possible of them.) We recommend that such space based telescopes be
built and deployed.
3.2 ALTER ASTEROID ORBIT
We support the proposal by
the
B612 Foundation
to significantly alter the orbit of an asteroid in a controlled manner
by 2015. They propose use of the gravity deflection approach, where
you station a spacecraft a short distance from the asteroid, and use
the gravitational attraction between spacecraft and asteroid to pull
the asteroid off course.
This method would be less likely to break up an asteroid than
alternative methods since there would be no physical contact with the
asteroid. You do not want the asteroid to break
into
multiple pieces as you will then have multiple problems instead of one
problem
[8].
Also note that a large asteroid could be blown apart by a
nuclear device detonated in its core only to have gravity draw the
asteroid back together, essentially nullifying the effect of the
explosion.
|
The schematic geometry of a Gravity Tugboat proposed
by the
B612 Foundation that is towing an
asteroid. If the distance d between the
centers of gravity of the asteroid and GT is equal to 1.5 r and the
half-plume angle ø is assumed to be 20
degrees the engines will each have to be canted outward by 60 degrees
and each will have to produce thrust
equal to the towing force. |
Many asteroids are "flying rubble piles" that are loosely glued together,
so you need to be careful when trying to alter their course.
Additional course altering methods include:
- Setting up "mass drivers" on the object to scoop up dusty
material and shoot it away, giving the object a slow, steady nudge.
- Flying a big sheet of reflective aluminized
PET film to wrap
itself around the asteroid, acting as a "solar sail" to use the
pressure of sunlight to shift the object's orbit. Dusting the asteroid
with titanium dioxide should have the same effect. Attaching an actual
solar sail to the asteroid would work faster than these solutions,
especially if the solar sail was hundreds of kilometers across. A
large solar sail would be nontrivial to build.
- Dusting the object with powdered chalk or soot to perform a
similar adjustment, utilizing the
Yarkovsky effect.
- Focusing solar energy onto its surface to create thrust from the
resulting vaporization of material. Or do the same with Earth based
lasers or microwaves. (Note it would be difficult to focus Earth
based beams millions of miles.)
- Have a spacecraft dock with the asteroid and then use its engines
to alter the trajectory of the asteroid. This would be difficult if
the asteroid was rotating quickly or was a "rubble pile".
If an asteroid was too close for you to have time to slowly adjust its
orbit, you might try:
- Directly altering its momentum by sending a spacecraft to collide
with the asteroid.
- Detonating a series of smaller nuclear
devices alongside the asteroid, far enough away as to not fracture the
object. This form of nuclear pulse propulsion would alter the
asteroid's course and hopefully not turn it into many asteroids.
-
Blowing it up with a nuclear weapon and then praying that no fragments
are
created
larger than 35 meters across. (Smaller fragments would burn up in the
Earth's atmosphere.)
- Attach an engine to it and then break it up by spin up.
This involves spinning the asteroid so fast it
breaks up sending fragments flying off into the solar system, hopefully
not headed towards Earth any more.
And if we detected the asteroid with plenty of time to spare, our
preference would be to:
- Consume the threat for profit. Now we're talking. This is our
favorite solution although it is more complicated than simply nudging
an asteroid a little.
The smallish near-Earth asteroid (3554 Amun) contains metals worth
about $20 trillion (that's not a misprint, it's trillion with a 'tr')
at today's prices [2].
3.3 CONCERNS
Carl Sagan, in his book
Pale Blue Dot, expressed concerns about
deflection technology: that any method capable of deflecting impactors
away from Earth could also be abused to divert non-threatening bodies
toward the planet. Considering the history of genocidal political
leaders and the possibility of the bureaucratic obscuring of any such
project's true goals to most of its scientific participants, he judged
the Earth at greater risk from a man-made impact than a natural one.
Sagan instead suggested that deflection technology should only be
developed in an actual emergency situation.
We share Sagan's concerns and believe more effort should be put into
detecting asteroids than deflecting asteroids.
|
|
|
4. CONCLUSION
Asteroid impacts are a concern and Hiroshima level impacts occur about
once a month but do not make the news because they have missed
populated areas so far.
We support efforts to locate asteroids that may impact Earth including
our Scientific Advisory Board member Nick Kaiser's efforts to locate
dangers with the Panoramic Survey
Telescope & Rapid Response System (Pan-STARRS) asteroid
early-warning system.
The worst way to deflect an asteroid is to attempt to destroy it. Not
only would this potentially cause the Earth to be hit by multiple
impactors instead of one, but it would waste a good source of space
habitat materials. We prefer use of the gravity deflection approach,
where
a spacecraft is stationed a short distance from the
asteroid, and uses
the gravitational attraction between spacecraft and asteroid to pull
the asteroid off course.
5. NOTES AND REFERENCES
1. George Friedman,
The Increasing Recognition of Near-Earth-Objects (NEOs),
Space
Manufacturing 10: Pathways to the
High Frontier, Proceedings of the Twelfth SSI-Princeton Conference, 4-7
May 1995, edited by Barbara Faughnan, AIAA.
2. J. S. Lewis,
Mining the Sky: Untold Riches from the
Asteroids, Comets, and Planets, Helix Books, Addison-Wesley
Publishing
Company, Inc.
3. J. S. Lewis,
Rain of Iron and Ice, The Very Real
threat
of Comet and Asteroid Bombardment, Helix Books, Addison-Wesley
Publishing Company, Inc.
4. Allan J. Willoughby and Melissa L.
McGuire (1995),
Adroitly Avoiding Asteroids! Clobber, Coax or
Consume?, Space Manufacturing 10, Pathways to the High
Frontier,
Proceedings of the Twelfth SSI-Princeton Conference, 4-7 May 1995,
edited by Barbara Faughnan, AIAA, pages 103-113.
5. University of Toronto,
Meteorite crash turned Earth inside out: study, June 4,
2004.
6. NASA,
A Study to Determine the Feasibility of Extending the Search for
Near-
Earth Objects to Smaller Limiting Diameters,
2003.
7. NASA,
The Threat to Earth from Asteroids & Comets,
2006.
8.
Leonard David, SPACE.com,
Supercomputer takes on cosmic threat,
June 14, 2006.
9.
John G. Cramer, Analog,
Killer Asteroids and You, July 1992.
10.
Robert Roy Britt, SPACE.com,
Asteroid Buzzes Earth, Highlighting Cosmic Blind Spot, March
19, 2002.
RESOURCES
Apophis Mission Design Competition by The Planetary Society.
Plans to put an electronic tag on Apophis, a 300-meter diameter
asteroid.
Earth Impact Database.
NASA Near-Earth
Object Program.
The Torino Impact Hazard Scale.
Why Build Orbital Space Colonies? by
Al Globus - ongoing
project.
ONLINE ARTICLES
20 Things You Didn't Know About... Meteors by LeeAundra
Temescu, Discover Magazine,
2006.
Are mirrors the best way to deflect asteroids? by David
Shiga, NewScientist - October 9, 2007.
Asteroid Hunters Receive Grants by Edwin L. Aguirre, Sky & Telescope,
2003.
Flying Rubble by Jeffrey Winters, Discover Magazine,
1996.
Hunting Asteroids From Your Backyard:
A convergence of technology has opened the realm of asteroid
discovery to virtually any backyard observer.
by Dennis di Cicco, Sky & Telescope,
1996.
New Cosmic Defense Idea: Fight Asteroids with Asteroids by
Robert Roy Britt, SPACE.com - June 20, 2006.
Technical Critique of NASA's Report to Congress and associated of
"2006
Near-Earth Object Survey and Deflection Study: Final Report" by
Russell L. Schweickart,
Chairman, B612 Foundation
and
Chairman, Association of Space Explorers Committee on NEOs
- December 28, 2006.
The End is Near:
The remarkable journey of a tough little space probe to the
place where killer asteroids lurk by Kathy A. Svitil, Discover
Magazine,
2001.
DVDS
Last Days on Earth, History Channel documentary about
potential asteroid collisions, 2007.
BOOKS
Asteroid Impact by
Doug Henderson, Dial Publishing - 2000.
Asteroids: A History
by Curtis Peebles, Smithsonian - 2001.
Death By Black Hole: And Other Cosmic Quandaries by
Neil deGrasse Tyson,
New York: W. W. Norton -
2007.
Hazards Due to Comets and Asteroids by
Tom Gehrels, Mildred Shapley Matthews, A. M. Schumann,
University of Arizona Press -
1994.
If an Asteroid Hit Earth by
Ray Spangenburg and Kit Moser,
Franklin Watts Press -
2000.
Mining the Sky: Untold Riches from the
Asteroids, Comets, and Planets by J. S. Lewis, Helix Books,
Addison-Wesley
Publishing
Company, Inc. - 1997.
Rain of Iron and Ice, The Very Real
threat
of Comet and Asteroid Bombardment by J. S. Lewis, Helix Books, Addison-Wesley
Publishing Company, Inc. - 1997.
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