There was brief anxiety earlier this year about the mile-wide asteroid 1997-XF-11, when initial calculations showed it passing about 30,000 miles plus or minus a hundred thousand miles from Earth in 2028. But this media panic faded abruptly when new calculations, supported by discovery of additional photos, showed that the 'close approach' was an artifact and there was no chance of a collision. But the preliminary prediction -- which never claimed more than a 1 in a 1000 chance of impact, despite how the news media hyped it -- is a foretaste of things to come when astronomers catalog more and more of the candidate impactors.
We already know what we're going to do about it. It's not just Hollywood and its blockbuster summer movies, or Dr. Teller and his plan to find a new mission for the US's nuclear arsenal. There is a remarkable national consensus of what the right thing to do is.
When we watch these movies, there is no doubt in the audience's minds that artificially saving the Earth by interfering with a natural process is the correct, ethical, and practical thing to do. There were no "Friends of the Asteroid" picketing Cape Canaveral to protest more filthy human interference in the affairs of Mother Nature. There was no moral ambiguity in the action taken.
The Universe threatens us. We resist.
What I want to address today is not merely the asteroid-deflection idea, which is certainly an extreme case, but the entire spectrum of deliberate human intervention in Earth's biosphere. We must as a society discover a strategy of responding to the many unintentional but global impacts of human industrial activity. An activist, interventionist approach to artificially repairing damage and threats to Earth's biosphere -- both accidentally man-made and randomly natural in origin -- is, I predict, going to be one of the most intense ideological and philosophical conflicts of the next century. And governments -- as well as their operational elements which would be tasked in carrying out these projects -- will be at the focus of this controversy.
The current ecological consensus centers on merely reducing human influences on climate. This relies on two unspoken assumptions. First, that Earth's biosphere has powerful self-governing stabilization and healing capacities. And second, that it is human activity which is the main threat to the stability of planetary climate.
I believe that both assumptions are highly questionable, at best. And furthermore, I believe that the most promising option has hardly even been mentioned yet. It involves deliberate artificial application of energy and material to intentionally force large-scale, even global, climate changes.
This new strategy will be based on scientific discoveries made in large part from space vehicles, and when implemented, will depend in large part on monitoring and manipulation from space vehicles. So every government entity which depends on space will be unavoidably involved.
Furthermore, considering the scale of the forces to be applied, and the reliably required, those US government entities with the greatest power and reliability will likely form the implementing teams. As we shall see from examples, purely scientific research groups do not appear to have the proper mindset to be trusted with the task. That leaves agencies such as NOAA, NASA, and the armed forces -- particularly the latter. When the country looks for a team with the capability and the integrity to be trusted with these tasks, it will have a very short list of candidates, and the US Space Command will be near the top of that list whether it seeks the mission or not.
I argue that the current strategy of "hands off the Earth" is a naive, superficial, and ultimately doomed approach, driven more by political ideology and internalized guilt-trips than by practical engineering. Here's why I think it's the wrong approach.
Human civilization is still enormously brittle, dependent on crop growth and other economic activities -- such as transportation -- that are very sensitive to climate fluctuations. Biosphere characteristics such as storms, wind and rainfall patterns, ocean levels, atmospheric transparency, and -- yes! -- outside influences such as solar variability and "falling rocks" have in the past made civilizations prosper, and doomed them. We are not yet that economically secure that such changes wouldn't have equivalent impacts on our civilization as well.
And it's not just a matter of a temporary retreat from modern capabilities, perhaps a fallback to eighteenth century technology that could later be made up again. Our worldwide developing civilization has eaten up all the easily accessible resources -- the near-surface oil, the easily reachable rich ores, the biological reservoirs of fish, game and timber. A future less technogically capable society would be unable to reach the oil and ores we now harvest. It would not be able, no matter how detailed the preserved blueprints and technical drawings, to reach and surpass where we are now.
So the "enemy" is not merely unintentional human pollution and land ravaging, no matter how visible and how graphic may be those and other anti-biosphere effects. The enemy is also Mother Nature with her wind and rain patterns, her biological interactions (including epidemics), her geologic threats, and even her asteroids.
Thus I believe that the ethic will arise -- hesitently at first, then overcoming fierce emotional and philosophical opposition -- that people will step in and interfere on purpose with natural processes.
I suggest an analogy with personal physical health. As a first step, certainly, do no harm. Avoid poisons and dangerous activities. Exercise and eat right. But we all realize that this is only "Part 1" of a 2-part strategy for health.
The second part is the activitist, interventionist phase. Vaccinate against possible outside infections. Surgically intervene to overcome systemic weaknesses or to forestall localized failures. Provide mechanical augmentation of degraded senses and muscles. Respond to external trauma with appropriate levels of care and repair.
This is how people stay healthy. And by analogy, it is how a planet should stay healthy.
By adding in the second phase of this philosophy to the care of Earth, we can begin to see technological solutions to technological AND natural problems. We can begin to see effective, affordable defenses against threats. And in the more distant future -- the subject of a subsequent talk -- we can glimpse desired engineered improvements to this planet, and ultimately to others as well.
Bluntly -- do we know enough now to take this kind of planetary responsibility? Can we guarantee that human meddling in climate won't have unintentional, deleterious effects? No, we don't know enough, and no, we can make no such guarantees.
But that is no more reason to avoid the strategy than the sad history of centuries of medical blunderings toward knowledge is a reason not to make use of modern medical science. The initial ignorance and misconceptions of medical workers were often more of a threat to patients than were the original ailments. But to a statistically significant degree we've passed through that prologue into the dawn of the age of effective medical science.
To refrain from taking actions in defense of Earth's biosphere, using the fear of our ignorance as an excuse, is -- I argue -- an abdication of our responsibility to our planet and to our nation and to our children.
Here's the Hollywood version: high-risk remedies are called for in the face of high-impact dangers. In such extreme situations, there is no moral ambiguity, no doubt about the "whether we should", only a debate about "which method is best".
Now, Hollywood and popular culture isn't always so explicit in accepting this theme. Look at 'Jurassic Park', where the Jeff Goldblum character, the chaos mathematician Dr. Malcolm, argues against the morality of resurrecting dinosaurs. Malcolm argues that "dinosaurs had their chance" but that "nature selected them out" based on some inadequacy of their species. We are hubristic and foolhardy to argue with the verdict of nature, Malcolm -- and millions of like-minded people -- insist.
Nonsense. Malcolm's assessment is wrong. We know why the dinosaurs died out. It was because they didn't have a space program. More specifically, they didn't have a NASA and a Space Command with the powers that ours soon will possess.
Many of the themes of 'asteroid defense' coincide with themes of intimate concern to the US Space Command. Perhaps the most pressing one is surveillance, the ability to know what is happenng out there. Ideally, one should know what is happening soon enough to take effective countermeasures.
For a future asteroid impact, given our current level of insight into the situation in space, the expected warning time before impact will be zero. Well, say, five or six seconds, since there will be a bright flash that a few people will notice before being pulverized.
Programs now in preliminary stages will be able to catalog more and more of the "Near Earth Objects" to smaller and smaller sizes, providing in most cases longer and longer advance notice of impact hazards -- but not for a few decades yet.
Among all the dangers that nature has dished out for Earth, there's a silver lining to the asteroid impact threat. The most likely objects to hit Earth are in orbits that repeatedly pass close enough to Earth to be spotted, tracked, and catalogued far in advance. Their orbital inclinations are close -- ten or twenty degrees off, at most -- and their orbital periods are within a factor of two of Earth's.
These objects constitute 99% or more of the impact threat, because the eccentric comets and deep-space interlopers -- while they exist -- usually have only one shot at Earth as they pass through the inner solar system. In contrast, these "NEO's" keep making passes again and again and again UNTIL they hit, or are flung clear by a very close approach.
The bigger objects -- the ten kilometer rocks -- are the dinosaur killers, the millions of megatons of explosive force. They are pretty well all catalogued and all look safe on a time scale of tens of millions of years.
The one-kilometer rocks, like 1997 XF 11 and a few thousand others, are the continent-killers, the thousand megaton exploders. About 130 of them have been catalogued, and NASA hopes to discover 90% of the rest over the next decade.
The 100-meter objects are the kind that made the 20-megaton Tunguska impact over Siberia in 1908. These are the city-busters, and we should expect them every few decades -- every century perhaps. There are hundreds of thousands of these out there and very, very few have ever been detected visually.
Even smaller objects hit more frequently, as you would expect. In 1965, a tens of kilotons mid-air blast over Revelstoke, Canada, scattered black dust across miles of new-fallen snow. A similar-sized object barely missed Earth, but entered our atmosphere and streaked across the Rockies -- not far from Colorado Springs -- and was videotaped by vacationers. Just a few years ago, a 100-kiloton-sized midair explosion over the western Pacific was startling enough that President Clinton was awakened to be informed of it -- it might have been somebody's nuclear weapons test. More will occur, and not merely over arctic waste, mountains, and open ocean.
There was worldwide near-panic in 1979 when Skylab fell back to Earth, and there has been understandable world concern about the safe disposal of the hundred-ton Mir space station, as it nears the end of its useful life. Russia has promised to steer it into the empty South Pacific when it crashes to Earth. Meanwhile, unnoticed and unwarned, several mini-asteroids as massive as Mir or Skylab fall to Earth randomly every year. So perhaps this illustrates how public attention is somehow misdirected towards manmade threats while correspinding natural threats are entirely overlooked.
In discussing what can be done about such threats, we come across a number of conceptual problems with the purely academic approach. It turns out that the operational skills possessed by NASA and the US Space Command are much more easily and reliably applied to this asteroid problem than are the theoretical skills of the scientific and intellectual community.
For example, Dr. Carl Sagan and some of his colleagues suggested that it was statistically more dangerous to build an asteroid defense system than simply to wait for the impacts. Their argument was based on the thesis that a system-in-being could under some circumstances be abused by "a madman" to deliberately divert otherwise-harmless objects toward an Earth impact. Although admittedly unlikely, this manmade danger was deemed MORE likely than the original natural threat of asteroid impact.
But this view is erroneous. The concern fails to account for operational issues in navigation, targeting, guidance and control, issues which real-world spaceflight operators deal with on a daily basis. By assuming that a space rendezvous -- bringing two objects into contact -- is merely an inverse process of avoidance -- guaranteeing that two objects do NOT come into contact, this concern is unrealistic.
The "avoidance" maneuver is already in the reportory of spaceflight operators today, in low Earth orbit. If the predicted path of a piece of space debris comes "close enough" (defined in the dimensions of the avoidance zone around the shuttle), the shuttle makes a small orbital adjustment to take it (and the zone centered on it) away from the predicted path of the candidate impactor.
Rendezvous is also routine in low Earth orbit, but it is a far different process than merely reversing the avoidance maneuver. As the active vehicle nears the target it receives more and more precise relative position data (navigation), which it converts into desired course corrections (targeting), which converts into required rocket burns (guidance), and which it then performs -- to the required level of precision -- using onboard rockets (control).
As the range and time-to-contact drops, so does the size of the uncertainty zone around the target, where the chaser is aiming. At the same time, the effect of rocket maneuvers on miss distance also drops rapidly -- they have less time to propagate and grow. Unless the approach is flown very precisely, the predicted miss distance can easily drift outside the "uncertainty zone" to such a great distance that the active vehicle's rockets simply cannot bring the aim point back onto the target fast enough. In other words, there is not enough "control authority" in the system. And the active vehicle flies past the target. The rendezvous fails.
For the proposed asteroid-deflection schemes of the next several decades at least, their control accuracy is far too poor to perform a "rendezvous", a deliberate collision, with Earth. Such systems would be fully effective in diverting dangerous asteroids, but would be physically unable to do the opposite, bring them into contact with Earth. As a threat for misuse, they would panic only those who don't understand real space operations.
Sagan however was not off base in raising the question about deliberately steering asteroids closer to Earth, because at some future point there will be excellent reasons to want to do this. Starting with the smallest trackable objects -- the 100-meter rocks -- it's plausible later in the next century to bring some of them back into high-earth orbit for mining. They contain commercially attractive amounts of metals and water, especially in competition with the cost of such materials brought up from Earth. And at a range of several hundred thousand kilometers from Earth, missing an orbital aim point by tens of thousands of kilometers will not matter.
And perhaps these asteroids' greatest resource -- one which military space planners half a century from now should be very interested in -- is simply the slag and dirt left over from mining. This material would provide shielding -- against impacts, against radiation, against visual inspection -- for otherwise-vulnerable space-based systems. Such mini-Gibralters in high orbit could become the literal "high ground" that space strategists have so far sought in vain.
Here's another example where today's experienced space operators already have a better grasp on required mid-century environmental modification operations. The obvious response to an approaching asteroid is to "deflect" it sideways to miss Earth. This is the mode for an approaching tomahawk in "The Last of the Mohicans", sure. But this "common sense" idea fails to appreciate the unearthly nature of out-of-plane dynamics in space.
Assuming a long-enough lead time, the last kind of impulse you would ever want to impart to an asteroid is perpendicular to its motion. This would merely make it wobble in its orbit, but it would for the most part still arrive at future points close to the original predictions.
Instead, the impulse should be directed ALONG its flight path -- slowing it down (from in front) or speeding it up (from behind) would work equally well. This would alter the energy of the orbit and cause it to arrive at predicted future intersection points at a different time. When it got there, the fast-moving Earth wouldn't be there -- and the impact would be avoided.
But try and explain this to someone unfamiliar with orbital operations. Tell them that in order to make it miss Earth, you want to SPEED UP the approaching asteroid, and see the reaction!
The US Defense Department may still be discussing for decades whether or not it wants to get involved in this business -- and in the end, the assignment may be dropped in its lap whatever its own desires may be. But already there have been very practical DoD interests in asteroids, and one of them is the probe Clementine-2.
Although Clementine-2 was line-item-vetoed last year by President Clinton, apparently on the advice of policy wonks that it might be misinterpreted as a space weaponization scheme that might upset the Russians, the recent Supreme Court decision overturning the constitutionality of the whole line-item-veto idea may allow the project to resume. It was always a good idea from the DoD's point of view -- test an autonomous microsatellite sensors and controllers -- but it is also very good idea from an asteroid deflection point of view, since it addresses the key unknown about asteroids, what is their internal structure and how would they respond to external forces (such as the US Space Command!).
Not long ago, astronomers thought of asteroids as rocks, perhaps rubble covered, but still mainly single bodies. But evidence has accumulated that asteroids are rubble piles all the way through, loosely bound together by what is generously called "gravity" (escape velocity is 11,000 meters per second on Earth but less than 1 meter per second on a typical small asteroid). The Shoemaker-Levy object was torn apart by a close brush with Jupiter in 1992 so when it fell back onto Jupiter two years later it was a string of smaller objects. Crater chains on the moons of Jupiter, on Earth's moon, and on Earth itself also point to the gravity-induced disintegration of many asteroids prior to impact. Asteroids which rotate fast enough to fling pieces clear are extremely rare -- only two are known -- which suggests that these are the rare single-rock objects.
What this means is that big impulses -- say, from another asteroid collision or from a nuclear detonation -- would more likely disperse the material than deflect it. Pushing an asteroid has been likened to clearing a landslide off a road, rather than rolling a rock.
So other techniques -- gentle pushes over long periods -- may prove to be required. There are plenty of such ideas. None of them will prove workable, I predict, but the second and third generation ideas will turn out to be quite feasible. And information from a reborn Clementine-2 may powerfully augment new astronomical discoveries.
Once the concept of asteroid deflection becomes widely accepted, in both practical and philosophical terms, we can move on to much more interesting and much more likely biosphere engineering projects. For many of them, the connection with the future US Space Command is going to be unavoidably profound.
By the way: If there's one class of modern intellectuals who do not find the idea of deliberate environmental modification to be incredible, it's the international lawyers and diplomats. There already is a treaty -- the Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques -- which was signed in 1977 and ratified in 1980. It defines "environmental modification techniques" to be "any technique for changing -- through the deliberate manipulation of natural processes -- the dynamics, composition or structure of the Earth, including its biota, lithosphere, hydrosphere and atmosphere, or of outer space." But all that is forbidden is doing this in order to create "widespread, long- lasting or severe effects as the means of destruction, damage, or injury." So peaceful uses are explicitly allowed.
The US Air Force's last major involvement with climate engineering was Project Stormfury, a quarter century ago. Attempts were made to steer hurricanes by preferential cloud seeding, to increase localized rainfall and heating. This was supposed to lead to alteration of the 'steering currents' which naturally and randomly direct a storm's motion. Results were ambiguous, except for the discovery that once you "touch" a hurricane, everybody blames you for where it eventually goes (of course, those living in areas the storm avoids do NOT come out to thank you). That's another reason for governments to do this -- so you won't be sued for damages. In any case, future projects to steer hurricanes -- or at least, mitigate their wind speeds when they do reach populated areas -- are only a matter of getting up the nerve to try it.
Equally daunting in a political sense is the question of earthquake control and the "geologic engineering" involved. The problem is not the slippage of tectonic plates, but their stickiness. They grab and hold as tension builds up (tension perhaps measurable in terms of magnetic field distortions observed by very high altitude sensor arrays), then break free all at once. Geologists have long known that near-surface fault lines can be "greased" or "fixed" by artificially varying the amount of water in the rock, and it has been proposed that known fault lines be massaged by fixing two end points and then deliberately slipping the inside region. This would allow a constant and low-force release of the energies. But for deeper faults lines, who in the government is going to suggest taking action to deliberately trigger an earthquake -- even though such an effort, at a predetermined time, would be far safer and probably much less damaging than simply waiting for it to happen at random? Here again it is not the science and technology but the politics and philosophy that stand in the way.
Global warming depends on many factors, of which greenhouse gases are only one component. The degree of cloudiness -- and hence, heat reflection -- is a factor subject to manipulation by high-flying aircraft. The degree of surface absorption of heat depends on ground albedo, which in turn can be controlled by area-wide plant cover -- another factor already being manipulated in semi-desert lands. And eventually the amount of solar energy falling on Earth's atmosphere could be modulated the same way we vary the heat coming into our cars and homes -- setting up blinds and shades.
Proposals to modulate solar insolation -- incoming energy -- from space have been discussed since the 1920s. Counting on the kinds of projects likely to get his government's financial backing, German space pioneer Hermann Oberth suggested using mirrors to concentrate sunlight to ignite forests in enemy territories, as Archimedes is said to have done with soldiers' shields to ignite the sails of an attacking Roman fleet. Less belligerently, Krafft Ehricke later worked out a sequence of peaceful terrestrial applications for very large space reflectors he called "lunettas" and (bigger) "solettas". NASA made some studies of its own, and their were even DoD studies in the 1960s to see if the Ho Chi Minh trail could be illuminated from space.
Five years ago, the first small "space mirror" was tested by the Russians -- they used a 20-meter diameter disk called "Znamya", held taut by spin, to reflect sunlight onto the Earth below. A follow-up test of a 25-meter mirror was planned for this November but has now been indefinitely postponed due to budget problems in the retreat from Mir. It could easily be rescheduled for an early mission to the International Space Station.
The biggest objections to the Russian space mirror project came from amateur astronomers, who prefer a night sky. But there were also environmentalist attacks on the proposed follow-on brighter project. Newspapers were full of accusations that space mirrors could upset the breeding habits of endangered species or could melt the Arctic ice pack.
Those accusations and objections are just a tiny foretaste of the kind of emotional clash that will be caused by any future proposals for artificial environmental modification. But in closing, I want to stress that this concept -- an activist, interventionist approach to maintaining our planet's health -- is going to slowly gain ground in coming years. And when the time comes to actually perform experiments and ultimately operational activities of this sort, it is going to be NASA and the US Space Command that will be intimately involved.