Imagine a potato 5km long and 2km wide hurling though space like a badly thrown football. Now imagine that spud crashing into your backyard and decimating the planet with the combined energy of millions of atomic bombs.



Such a collision would destroy most of life on Earth. Any surviving cockroaches would be mighty pleased, however.

“The space spud is PHA (Potentially Hazardous Asteroid) 4179. French scientists discovered the asteriod in 1989 and named it Toutatis after the Gaulish god of Thunder and Destruction. Toutatis' peculiar shape, wobbly rotation and wacky orbit make it unique among the near-Earth asteroids whizzing around our blue planet. Scientists at NASA's Jet Propulsion Laboratory in Pasadena, Calif., study these space rocks with radar. [. . .]

“Orbit-altering experiences with planets Earth, Mars, Venus and Jupiter, as well as the Sun, make Toutatis consistently inconsistent, passing closer or farther to larger bodies as gravity wills. On its most recent visit, October 31, 2000, Toutatis passed within less than 29 lunar distances of earth (a lunar distance is the average distance from Earth to Moon: 384,400 km). When Toutatis is next in the neighborhood (galactically speaking), on Sept. 29, 2004, it will pass just 4 lunar distances from Earth. The asteroid will be the brightest it's ever been and easy to see through binoculars.”

The concept of a large meteor like this one eventually breaking thru our atmosphere and trashing the Earth is hardly just Hollywood fluff. It’s been surmised by several scientists that an asteroid just like Toutatis struck what is now Mexico about 65 million years ago and effectively ended the dinosaur age in one fell swoop.

Nor is this a mere tale of bygone days. On March 23, 1989, an asteroid with a kinetic energy of over 1000 one-megaton hydrogen bombs (i.e., about 5,000 times more powerful than the bomb dropped on Hiroshima) was recorded to have passed very close to Earth. Named 1989FC, scientists only discovered the closeness of its pass to the Earth after the fact, during a calculation of the asteriod’s entire orbital path.

Then in 1994, the new Spacewatch Camera in Arizona discovered four asteroids that sped by twice as close to us as our nearest neighbor, the Moon.

News of these activities brought what are called Near Earth Objects (NEOs) into the political arena.

What--if anything--are scientists and governments doing about this? Is it that much of a concern, or were those close passes simply freakish accidents, horrible things that--thankfully--almost never happen? S.O.S. investigates.

Getting a Grip

Asteroids, like comets, are really just chunks of flying debris left over from the formation of the solar system about 4.5 billion years ago. Some are huge; for instance, the potato-shaped asteroid Eros is bigger than the whole District of Colombia.

Before you freak out entirely, it must be noted here that the statistics on the chances of an NEO over one kilometer (3,000 feet) long--about the size of the one that probably killed off the dinosaurs--hitting the Earth soon are practically nil. A hit by such an asteroid is unlikely to hit Earth for hundreds of thousands of years. By then we’re probably sure to have something to at least alter the NEO’s course . . . if we’re still around, that is.

And because many asteroids heading for us end up bouncing off our atmosphere or principally burning up on entry, there aren’t many asteriods that can get thru and maintain the size necessary to cause widespread damage.

The statistics on smaller hits are vague and subject to change, however. In the general press, too little coverage is given to the small asteroids which could conceivably cause terrible local destruction (e.g., to nearby coastal cities) but little worldwide impact, and which probably hit once every hundred years.

Also, our current best telescopes can hardly see the 100-meter asteroids because they’re so small; hence the vague statistics.

Still, "Near Earth Objects"--the term "near" is a pretty relative one, since it refers to space debris within a third of the distance to the sun--pose a threat to all nations.

For instance, a reasonably large asteroid of 200 meters (600 feet) in diameter crashing into the Atlantic Ocean could create a tsunami (a giant tidal wave) that would sink both Britain and the entire East Coast of the United States within minutes.

Up to the 1970s, there was actually little interest in asteroids, including NEOs. They were considered little more than low class astronomical objects. Indeed, the small comet which destroyed hundreds of square kilometers in remote Siberia in 1908 was an event little known to the general public. And a small asteroid which skimmed the upper atmosphere in the 1970s, as detected by a US military satellite, received little publicity.

Things began to change in the late 70s. A small but increasing number of astronomers interested in asteroids began to be concerned by the abundance of these objects passing close to the Earth. They instituted processes to catalog the asteroids accidentally seen on telescopic plates that had not previously been recorded.

Theoretical computer models revealed that the gravity of the planets caused a sizeable number of asteroids from the Main Belt between Mars and Jupiter to cascade down into lower orbits, with many approaching the Earth. Further, a significant fraction of comets passing thru the inner solar system would be diverted into orbits near Earth, due to gravitational encounters with the inner planets.

As a result of these discoveries, the estimated number of NEOs expanded by about 1000 times.

After that, some in the know say half-jokingly, even scientists and government officials began taking notice.

The ever-improving U.S. Defense Dept. sensor technology used to spot the satellites of adversaries began inadventently recording a surprisingly high frequency of asteroid fly-bys, some viewed as meteor fireballs hitting Earth’ s upper atmosphere. A tedious part of this process however was discriminating between man-made satellites and distant asteroids.

New telescope technology (CCDs) emerging around 1990 increased the discovery rate of all asteroids and eventually confirmed their abundance via solid statistical sampling rates. In fact, it is now estimated that there are about 300,000 Near-Earth Asteroids over 100 meters (about 300 feet) in diameter, and about 2,000 over 1 kilometer (3,000 feet) in diameter.

What does that mean to us? Well, if an asteroid at least 1 kilometer in size hit Earth, it would cause a dust cloud which would block out sunlight for at least a year and lead to a deep worldwide winter, exhausting food supplies. The latter is what caused the dinosaur extinction.

Many scientists estimate the impact by a single 1-km object could kill up to a quarter of our planet's population.

Smaller hits--about 100-200-meters (300-600 feet), say--are far more common. Unfortunately for research, their effect doesn’t show up much in global geologic histories. It is estimated, however, that such hits have created many local tsunamis and brief climate changes in recorded history, without any understanding of their cause at the time.

The 1989FC near hit prompted a division of the American Institute of Aeronautics and Astronautics (AIAA), the Space Systems Technical Committee (SSTC), to publish a position paper in April, 1990, entitled "Dealing with the Threat of an Asteroid Striking the Earth." This paper was submitted to the US Congress as part of the AIAA's annual testimony.

The U.S. House of Representatives' Committee on Science, Space and Technology was moved by this submission and stated, in the NASA Multiyear Authorization Act of 1990:

"The Committee believes that . . . the detection rate of Earth-orbit-crossing asteroids must be increased substantially, and that the means to destroy or alter the orbits of asteroids when they do threaten collisions should be defined and agreed upon internationally. The chances of the Earth being struck by a large asteroid are extremelly small, but because the consequences of such a collision are extremely large, the Committee believes it is only prudent to assess the nature of the threat and prepare to deal with it."

Though Congress directed NASA to conduct two workshops according to the AIAA's recommendations, and the final reports (click here and here to view) were presented to the Committee on March 24, 1993 in a hearing entitled "The Threat of Large Earth-Orbit Crossing Asteroids; Hearing Before the Subcommittee on Space of the Committee on Science, Space and Technology, U.S. House of Representatives," little was actually done due to budget cutting and intense competition between traditional recipients of NASA money.

With no significant new funding coming from Congress, initiative quickly fizzled.

But in 1995, the AIAA released an update to their previous position paper, entitled "Responding to the Potential Threat of a Near-Earth-Object Impact," recommending four actions:

1.) Support of an accelerated detection program

2.) Start systems engineering studies immediately

3.) Perform laboratory and/or in-space tests of any key elements

4.) Establish a central management and information system regarding activity in this field, both US and international.

It’s also said by many that an asteroid early warning system is much simpler and less expensive than the SDI/"Star Wars" plans that have resurfaced recently, and would give much better economic spinoffs. At the same time, the cost of an accelerated detection program plus a rapid deployment force are very small compared to the damage due to a hit by a small asteroid.

In the 1995 paper NASA promised to identify all potentially dangerous space objects by 2005. NASA currently spends about $2 million annually on NEO identification, but has fallen far behind the original schedule. (If you wish to look at all major Congressional hearings and statements regarding NEOs, click here.)

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Taming the Satellites

Apparently worried that NASA may have blown a golden opportunity, in 2000 a blue-ribbon scientific panel based in London called the Task Force on Potentially Hazardous Near Earth Objects called for Britain to spend “ as much as $100 million on a defense system against space objects, with a blueprint similar to the military's missile defense systems--an early detection network coupled with some means to stop an incoming threat,” according to a later story by the Washington Post. [Note: The chapters themselves are in PDF format, found at the bottom of each chapter webpage. The link to each chapter also provides a short, hypertext summary of that chapter’s contents. Don’t confuse the hypertext summary with the detailed chapters in PDF.]

The Post said the panel “recommended that Britain take the lead in defending the people of our planet from an overhead threat of . . . killer asteroids.”

Perhaps sensing that much of the public may find such statements alarmist, Britain's science minister, Lord Sainsbury, was quick to say, "This is not science fiction . . . The risk is extremely remote . . . but it is real. We put a lot of money into astronomy. It's sensible to put just a little bit into making certain we know if there is any danger of an object hitting our very fragile planet."

The detailed report describes probable impact damage and death tolls for asteroid/comet hits of various size and composition.

But it also spends some considerable time talking about how, with enough advance warning, we could save several lives by moving large population segments away from the impact zone. It reminds us there would still be severe destruction, fire storms, envirnomental impacts, etc. to deal with.

It also adds that it “would be difficult to sustain the population during the long period which might follow when the Sun's rays were blocked by dust injected into the atmosphere at the time of impact.”

The only realistic course,” the study surmises, “would be to try to avert the predicted collision.”

The task force report urges construction of new telescopes, particularly in the Southern Hemisphere, which has fewer astronomical installations. Their increased numbers could help astonomers spot a potentially dangerous NEO more quickly.

The panel recommended spending about $24 million immediately on a new 10-foot telescope somewhere south of the equator. The team also suggested launching "Spaceguard" satellites to watch for incoming destruction.

They insist an asteroid racing toward Earth might then be spotted a year, a decade, or even a century before impact. The task force suggests destroying or deflecting the unwelcome visitor. The report doesn't provide specifics, but U.S. nuclear scientist Edward Teller has suggested using nuclear bombs in space to nudge an asteroid off a collision course with Earth.

Many others, including those who created the British report, are unsure about using weapons that could potentially blow up the asteriod, even if that wasn’t its intention, since the pieces could still rain down on Earth.

According to some, the task force paper also suggests we may need this know-how sooner than many of us think.

According to these individuals, Asteroid 1998 OX4 has been identified as having some real statistical possibility/probability of impacting the Earth this century.

Asteroid 1998 OX4 is a 300-400 meter wide asteroid predicted, they say, by NASA and other authorities to be on a possible collision course with Earth.

At about page 50 of the report, they say the task force identifies three asteroids whose collision with Earth cannot be ruled out. Two of them are, they assert, too small to cause any real damage on the ground; they would probably burn up in the Earth’s atmosphere.

That leaves 1998 OX4, whose projected impact "has not been ruled out." They say the task force give dates of 2014, 2038, 2044 and 2046 as possbile "impact years."

According to the estimates they say is found elsewhere in the Report (thought they did not clarify where), an impact by this asteroid could:

1.) be anywhere from a "Large sub-global event" to a "Low Global Effect Threshold" event;

2.) leave an impact crater 6 to 8 Kilometers wide;

3.) be expected to kill "on average" somewhere between 500 thousand and 1.5 billion people;

4.) totally destroy an area the size of Delaware;

5.) release an energy equivalent of up to 1,000 Hydrogen bombs.

This asteroid is referred to as a “double Earth crosser,” which means its orbit crosses the Earth’s twice. It comes around about every two years (or every 723 days) during its orbit.

Which means it will, of course, be back around in 2002, 2004 and 2006 . . . The task force, these individuals say, denies any potential risk those years.

Though S.O.S. gave only a cursory examination of the large British report on NEOs, it could find no direct evidence of the data quoted by these individuals.

However, in what appears to be a clear but little-known response to the 2014 impact possibility, S.O.S has verified their claim that the report does refer repeatedly to a NASA test probe, due to be launched in 2004, called Deep Impact - yes, that’s its real name - that will chase Comet 9P Tempel 1 and launch a half-ton, solid copper projectile into the comet's nucleus in 2005, to see if the sudden weight can alter its orbit.

While the comet is not a “real threat” to the Earth, the mission is meant to give us experience in how to alter the orbit of the real thing.

The quicker such an operation can be performed on a potentially damaging NEO, the report says, the better chance we will have for a successful escape from a terrible end.

Cruel, Cruel Fate

Luckily, Earth's atmosphere gives protection against the vast majority of small asteroids. Asteroids hit the atmosphere at typical speeds in excess of 10 km/sec. Those whose entire orbits reside within the inner solar system hit with an average of about 20 km/sec - with exact relative speed depending upon their angle of approach - and with speeds over 50 km/sec common for small cometary objects making a pass from the outer solar system.

At this speed, they usually break up due to severe shock pressures, and burn up due to friction with the atmosphere. Think about it -- 10 kilometers per second (6 miles per second) is bone-scrapingly fast -- about 36,000 kilometers (22,000 miles) per hour.

For asteroids coming in at 20 km/sec, it's generally thought that to penetrate the atmosphere and cause major damage by tsunami, an iron asteroid must be around 40 to 60 meters in diameter, and a stony asteroid 200 meters in diameter.

However, a stony asteroid 60 meters in diameter can cause significant damage by explosion due to atmospheric influence.

The exact damage inflicted by an asteroid or comet depends upon a number of factors -- size, speed, composition of object, and whether it hits land or ocean.

For a land impact, it can be said that an object of roughly 75 meters (225 feet) diameter can probably destroy a city, a 160-meter (480-foot) object can destroy a large urban area, a 350-meter (1050-foot) object can destroy a small state, and a 700-meter (2,100-foot) object can destroy a small country.

Smaller objects can cause far more widespread damage with an ocean impact. The effects of an ocean impact are felt much further away than the effects of an airburst due to the more effective generation of water waves, and the fact that human populations and assets are largely concentrated in coastal cities.

For example, the earthquake-induced tsunami in Chile in 1960 produced waves in Hawaii 10,600 km away of height up to over 10 meters (30 feet), and up to 5 meters (15 feet) in Japan 17,000 km away with an average of 2 meters, causing heavy damages and loss of lives.

The damage caused by a tsunami is due not just by a heavy wall of water hitting things, but much more to the solid debris carried by the powerful, churning deep water wave as it hits the continental shelf--the solid debris rams and batters anything in its way.

The 1998 earthquake-induced tsunami in Papua New Guinea that wiped out coastal villages and killed uncounted thousands of people was only a few meters high. If an asteroid hit the ocean, we could see a tsunami wave 100 times higher.

Such a tsunami would cause unprecedented damage to now-developed low lying areas all along the U.S. east coast, and may totally submerge vast areas in Europe such as Holland and Denmark. A 100-meter (300-foot) tsunami would travel inland about 22 km (14 miles) and a 200 meter (600-foot) tsunami would travel inland about 55 km (34 miles).

Stopping it All

Unlike most other problems you might have encountered in your readings at S.O.S., there simply is no good way to fight or run away from a killer asteriod - not alone anyway. As the British task force report shows us, we may together be able to stop an asteriod from wiping out so many lives, human and otherwise.

The trick? Early, early detection, and quick, effective interplanetary action by the big powers.

Fine, but how can this be done? The Task Force on Potentially Hazardous Near Earth Objects writes:

“A number of possible mechanisms have been considered for deflecting or breaking up potentially hazardous Near Earth Objects; most would require the use of a spacecraft with some means of transferring energy or momentum to the object, for example by kinetic energy transfer (by heavy projectiles carried on the spacecraft or by causing a collision between asteroids), by chemical or nuclear explosives, or even by mounting "sails" on the object to harness the Sun's radiation pressure.

“Some of these mechanisms are more realistic than others. [. . .]

“To try to destroy an asteroid or comet in space by a single explosive charge on or below its surface would risk breaking it uncontrollably into a number of large pieces which could still hit the Earth, doing even more damage.

“A more promising method would be to fly a spacecraft alongside the object, perhaps for months or years, nudging it in a controlled way from time to time with explosives or other means.

“This relatively gentle approach is particularly important because many asteroids and comets are held together only by their own very weak gravitational fields. The longer the time before impact, the more effective even a small nudge would be.”

There have been many scientific analyses on alternate ways to deal with a large object on a collision course with Earth.

The methods can be roughly split into two categories--destruction and deflection.

Destruction means breaking up the object into pieces small enough that none can penetrate the Earth's atmosphere. For example, if done by nuclear detonation, the dispersion of the fragments would mean that most--but not all--pieces would miss the Earth.

The further away the detonation, the more dispersed the pieces by the time they arrive in Earth's vicinity. As you can see, blowing up the object is actually a combination of destruction and deflection--the dispersion is a sort of deflection. The problem with destruction is the uncertainty of explosions. Success is risky.

Deflection means simply nudging the body so that it misses the Earth. The further away the object is from Earth, the less we need to nudge it because the change in its trajectory adds up over time.

If we detect an object on an impact trajectory, then we will need to make a decision on a method of planetary defense. The method chosen will depend upon the size of the object, how soon we can rendezvous with it, of what the object consists, the rotation rate of the object, its geometry, and any fractures in the object.

There would be considerable uncertainty regarding the composition of the object without a thorough on-site visit. For analysis purposes at this point in time, models have considered objects consisting primarily of ice, friable material, gravel, hard rock and pure metal.

Most proposed methods have been rejected due to risk and economic and/or technical feasibility in the near future. The remaining methods seriously considered to date include:

1.) Blowing it up by nuclear bomb--This option is generally unfavored because it seems unlikely that it would completely break up most objects well enough, or assuredly move all pieces into a non-impact trajectory.

It's still considered because it is economical and technically feasible--it might work, and it might be all we can do if given extremely short notice.

2.) Nudging it by nuclear bomb--This option explodes a nuclear bomb above the surface of a volatile asteroid or comet, causing intense heat at the surface in order to create gas jets which would thrust it away from Earth.

Another nuclear nudge option is to blow off a piece by targeting an existing natural fizzure, splitting it in two so that both dangerous pieces miss the Earth in a straddling way.

The drawback to both options is that both are often considered too ‘slick’ for scientists to be certain of their results. However, it very well might work, and it might be the most reasonable option if given very short notice.

3.) Nudging it by kinetic impact--This option simply has a sizeable object strike the asteroid or comet at high speed in order to nudge it, possibly with an explosion upon impact to enhance the effect. This could work with small objects. The risk is that it will fragment the target and put a sizeable chunk on a collision course with Earth.

4.) Thrusting the object--This precludes utilizing something on the asteroid that can be used to propel the object from its current trajectory. This option is attractive for very small objects whereby it would be feasible to send up to the asteroid a very high performance engine with the required fuel propellant for the move; for small to medium sized objects known to be rich in water, we could use it as fuel propellant in a thermal rocket.

Nuclear rockets (which use a small nuclear reactor to heat any kind of propellant) would be preferred for their simplicity and high performance.

Notably, solar ovens would not be preferred in the immediate future compared to a nuclear thermal rocket. Lack of simplicity, uneven performance, and the possible need to clean dirty mirrors argue against the solar device.

The advantage of thrusting is that the object won't be fragmented, giving us more control. The disadvantage is that it won't handle very large objects in a short time frame.

If an object were approaching Earth and we were given sufficient time, we could send out multiple missions using different techniques. If the first mission failed, a second mission could give it a shot. If an earlier mission fragments the asteroid, a later mission could deal with a fragment on a collision course with Earth. If it's a large object, it could fragment into multiple threats.

But in all cases, the more advanced notice we have, the greater our chances for success. The experts agree that time is the critical element which can make all the difference in the world.