Comet Impact!
Jacob Schwartz
When the comet Hale-Bopp approached Earth in 1996-97, it looked like a starry cue-tip with a fuzzy ball of light trailed by tapering cotton candy. When astronomers talk about death from above, it's just such a cue-tip swimming against a field of stars and galaxies that does it.
The most likely person to spot such a distant moving innocent looking villain would be an amateur astronomer. Thousands of them nightly patrol the skies with telescopes and binoculars hoping to discover a comet, or an asteroid, that might later bear their name. Having noticed such an object, the astronomer checks charts and maps to see if the object has already been observed, such as one of the 10,000 or so asteroids with computed orbits, or a comet. Then the next night, the astronomer would re-visit the same section of sky observing if the new object moved. And suppose it does move, and suppose you're the astronomer, and you calculate the path of this thing, and discover it could collide with Earth. Then you check it again, and reach the same conclusion.
The first thing the typically skeptical astronomer would do is send an e-mail or telegram to the Harvard-Smithsonian Center for Astrophysics in Cambridge MA, and specifically to Brian Marsden, a portly white-haired astronomer with the bright eyes and enthusiasm of a man with a profession of solving astronomy puzzles.
Comets are huge chunks of ice and rock leftover from when our solar system was made. Most of them are way out in space, beyond the reach of the most powerful telescopes. Some approach the Sun, and on their way sometimes come near Earth. As comets approach the Sun, the ice comprising them melts a bit and forms a vapor trail stretching hundreds of miles long.
Asteroids, on the other hand, are made of rock and no ice. The rock is usually comprised of the same metals on Earth. Most asteroids are in a wide belt of sky between the planets Mars and Jupiter, but thousands are closer and cross our Earth's orbit. Marsden has been announcing the arrival and departure of these comets and asteroids for many decades, like an airport's public address system announcing arriving and departing flights.
Let's say that Marsden checks out the discovery of our hypothetical amateur astronomer and his or her cue-tip. Marsden will first calculate if the object might strike the Earth. Let's say that initial indications show the object having just a slight chance of striking our planet. He then sends out an alert, and within hours dozens of astronomers all over the world focus eyes and equipment on the new visitor. They know that many calculations over several days and weeks, and from different perspectives, are necessary to calculate orbits precisely enough to predict an earth impact. This is extremely serious business, and errors are not taken lightly. No one wants to frighten humanity unnecessarily, and neither do they want to ignore a dangerous invader.
Let's further assume that the comet enters our star system on the far side of the Sun, but comes very close to the Earth's orbit on the outbound journey returning to its lair in the dark recesses of our system. Yes, it will be visible to the naked eye just as Hale-Bopp was, with its vaporous tail stretching across the night sky. Comets hardly ever threaten the Earth, but maybe this one is the exception. Let's say the hypothetical comet will come so close that the Jet Propulsion Laboratory (JPL) at the base of the San Gabriel mountains near Pasadena California is alerted, similar to the scenes in the film Contact featuring Jodie Foster. Radio dishes are alerted in remote areas of Spain, Australia, Chile and Puerto Rico. Astrophysicists place the few observations of the new comet into their computers, scan the data, and blink! Yes, the new comet is approaching Earth with a small but real possibility of impact. More calculations are necessary.
The JPL further calculates the path and speed of the comet and construct a graphic display with impact probabilities displayed by elliptical, egg shaped, lines meant to represent possible trajectories of the comet. The Earth's orbit is indeed somewhere very close to the comet's expected timetable of arrival into close orbit around the Sun. And, gosh, the comet could hit us.
Now the global messages multiply with alert bulletins to all observatories capable of precisely calculating the comet's orbit. More prestigious astronomers studying quasars and black holes are pushed aside by the lowly solar system specialists eager to be important in calculating a possible threat to our very existence. Even the Hubble Space Telescope is enlisted to track the possible villain.
Virtually all astronomers examining the data conclude the comet will swing close to the Sun, increase in velocity from the centrifugal force and on its outbound journey have a 20 percent probability of hitting Earth. Why a probability? For one, orbits of newly discovered objects always have some errors partly because the background position of stars contain their own residual errors. Second, as the comet approaches the Sun and warms up, gases within its icy core warm and burst much like geysers. And all this activity can change its speed and trajectory. No one will know whether impact will or will not happen until about only twenty days in advance.
With so many laboratories and observatories hot on the track of this threat to our very existence, the press has gotten wind of the story and drawings of the predicted orbits of the comet and its impact with the Earth are splashed onto newspaper and magazine covers around the world. The countdown is 89 days to impact.
What would happen if people around the world realized we may all die in three months. Would computer operators quit their keyboards, would stocks soar or decline, would we all max out credit cards and head for Pago Pago, would banks fail as depositors withdraw savings? Would the doomsday naysayers crawl out of the woodwork and beat themselves while chanting Biblical verses or passages from the Tibetan Book of the Dead? There's no precedent for this scenario since the whole planet has never been so clearly threatened by an outsider before. Or would we continue to do what we usually do, but with a bit more theatrical bravado and anxiety? Perhaps shy persons will have the inspiration and courage to approach the potential friends and lovers admired only from a distance? And would those of us who have spent a life accumulating money and possessions suddenly feel better, whether relieving guilt or responsibility, just by letting it go.
As the comet approaches the Sun, people all over the world will have an opportunity to see the comet coming closer and closer to the Sun and then enlarge as it neared us. And everyone asks "Will it hit, or will it fly away." Military leaders of nations with missile capabilities confer on whether it will be possible to knock the comet out of the sky if it comes too close. Some scientists support the idea, while others warn against the impact of the resulting debris. Binocular and camera sales zoom, church attendance surges, psychics and spiritual teachers urge visualizing the comet speeding past the Earth undisturbed on its return to the darkness of outer space.
The gentle curve of the comet's trail in the evening sky cautions all of us to distrust beauty and nature itself. How can something so attractive be so deadly? For a few days the comet ducks behind the Sun and our anxiety reaches a new high. Some wishfully proclaim it has left us, while others fearfully bite their nails or have sleepless days and nights dreading its return. The Hubble Space Telescope can be turned into an oven simply by aiming its lenses to the Sun, but the risk is necessary and the safety protocols are ignored. The comet emerges from behind the Sun and Hubble picks up the image then broadcast to every computer and news organization in a frightened and weary world. Fine tuning their calculations, scientists grimly announce the news is even more frightening than at first estimated. The probability of impact has risen to 75 percent.
Remember that Earth travels around the Sun at a speed of 66,500 miles an hour, and our rendezvous point with the comet is 10,000,000 miles away. But we know we'll reach that point, and so will the comet. The comet dominates our nightmares and coming so close, it can be seen in broad daylight, its fuzzy cue-tip cotton candy conical tail silhouetted against the blue sky.
As the comet nears, small fireballs light the sky from the debris exploding out from it. One of the rocks exposed in its melting ice flakes off and bores a hole in an English office building, forest fires are ignited from other fireballs landing in Brazil.
The comet hits the South Pacific ocean near an island in the Tahiti chain. The explosion vaporizes air, water, and land creating a 200 mile diameter crater in land and sea. The tsunami and roar roll around the world, and the mountainous splashes impacts the western coast of Canada, Washington, Oregon, California and Mexico simultaneous with Australia, Hawaii, and Indonesia. The roar of the impact soon follows. The fifty foot waves move steadily at a speed of 500 miles an hour.
The floods now begin to be felt in Asia and Africa as the wave moves around Australia into the Indian Ocean and in the opposite direction around southern South America and into the Atlantic. Florida and northern Brazil is submerged. Before the day is over, all of the low lying areas of the Earth will be submerged from northern Germany to Hong Kong, from New Jersey to Southern Africa.
In the final assessment of damage, fire is the greater threat. Fireballs coming from the comet approaching the Earth become ever larger and more frequent as the gravitational forces within its core go wild. The explosions move out in all directions, filling the night sky with fireballs creating forest and urban firestorms. Some of the nuclear warfare detection systems automatically confuse these fireballs hurtling through space at tremendous speeds as invading nuclear warheads from an unknown enemy; counter attacks are mistakenly dispatched in response. And we have a nuclear war by mistake. Thousands of fireballs are extinguished before reaching Earth's surface, but too many more thousands make it intact and their heat and thrust ignite everything around them. Soon the world is ablaze, and the air is black from the fine dust and smoke. The Sun is invisible even at midday, and the rain is so rich in sulfur dioxide and toxic metals that any surviving plant and animal life is extinguished -- life near the surface of the Earth. The only creatures to survive are those we know the least about, the animals and plants at the bottom of the oceans kept alive not by light but by the heat from geysers on the ocean floor heated by the inner Earth's molten magma. Those humans, however resourceful who manage to survive the blast, fires and flood will find themselves facing starvation. In the worst case scenario, when greed reaches its ultimate, nuclear nations will blackmail those without nuclear weapons for whatever food and water remains. But the inevitable doom is only temporarily delayed. We begin what Carl Sagan once called the "cold and dark of a nuclear winter". Small enclaves of humans, plants and animals may survive a comet impact, but civilization won't.
Accepting Rocks from Space is New. Until recently, scientists denied that stones come from the sky at all. Comets were considered "vile stars" by the ancient Chinese, and Europeans in the 17th century saw them as ghost ships in the sky bringing disaster for earthly sins. But debris from these comets, now known as meteorites, were unknown. As late as the 19th century, scientists looked upon meteorites (chunks of comets or asteroids) as superstitious folklore, not accepted by rational people. Holes in torn roofs and rocks beneath were considered by academicians as deceptions. Scientists felt that anything not already understood in physical terms must be superstitious rubbish.
However, since these rocks reported from heaven had such a different chemical compositions than rocks in their immediate surroundings, scientists were forced to entertain an extra-terrestrial origin for them. When two thousand rocks fell on a French town in April 1803, the Academy of Sciences investigator was reluctantly forced to acknowledge stones from space. Geologists up to that time attributed the craters both on the Moon and Earth to come from volcanoes only, not from impacts of solid bodies from space.
In fact, the more scientists were able to observe the surfaces of Mercury, Mars, and the solid satellites of Jupiter and Saturn, the obvious conclusion emerged that the solid spheres of our solar system have always been targets for invaders. The theory of volcanic origin for most craters is now discredited. Those depressions came from outside, not inside. Were it not for erosion from wind, rain and geological upheavals, Earth would be as pock marked as our Moon and neighboring planets. In fact, the showers of meteors that happen periodically, what we call fallen stars that quickly streak across the sky, may be the rocky residue of comets having passed this way leaving a trail of rocks that Earth passes through every year. The most impressive meteor showers occur every year about January 3 (Quadrantids), August 11 (Perseids), October 21 (Orionids), November 18 (Leonids), and December 13 (Geminids). One of the largest meteor showers this century is expected November 18, 1999, reminding us all that a comet once passed here, and might have impacted Earth if the timing was different. Another millennium precursor of doom? or a signal for a new enlightened millennium?
Have we had a preview of the above scenario. You betcha! On March 23, 1993 during a routine observing run, the husband-wife team of Carolyn and Eugene Shoemaker, and the amateur astronomer David Levy, spotted a strange object on their photograph. They reported a strange smear near Jupiter that was later revealed to be a comet torn into fragments by the Jovian tidal forces. Just as in the scenario above, scientists around the world were alerted and observers collectively predicted, for the first time in recorded history, impacts by a series of cometary fragments onto Jupiter. Sixteen months later in July 1994, the Shoemakers and Levy witnessed the comets named after them bombard Jupiter, one iceberg after another, battering and scarring the Jovian atmosphere with black wounds taking many weeks to heal. Had Jupiter been Earth, we would all be dead now. After that experience, we all took our solar system more seriously. Any dinosaur you ask will tell you Earth is a dangerous place!
The good news however is that such impacts happen every hundred million years. However that doesn't mean we are guaranteed a hundred million year interval between impacts. An impact is as likely to happen three months from now as a million years from now. We simply don't know.
The above worst case scenario is a story and written as a vaccination against the negative, fearful thinking becoming ever more popular before milennia. Can any of us survive a direct comet impact? Probably not? But what will negative thinking bring: negative results. Thoughts are things, what we envision can happen. While the scientific estimates of likely scenarios are very real, the above is written as fiction and not fact, as a wake up call to respect the purpose and gratitude for the life we have however difficult it appears to be.
The common expectation is that the neighborhood of time called 2000 will bring a new era of destruction, enlightenment, both or neither. Whatever happens, are we ready for a leap of trust to embrace new forms of body and consciousness. Are we so attached to a physical body, that another richer form of spirit seems impossible if not ridiculous? If your answer is in the affirmative, then you've been trapped by the demon of fear, weakness, and vulnerability to uncontrolled reaction; no explanation is possible. If you trust a spiritual or etheric body thrives alongside the physical, another level immune from mortality, forms, time and space, then no explanation is necessary.
But if you live your life expecting such a calamity. Buy into negativity , then negativity is what you will live. If there's any moral lesson here, it that every moment counts, and it'
s in the moment that live is the most enriching. Living in the memory of the past, or in the anticipation of an uncontrollable future, is living in another time and not now. The only real life is this very moment.
SIDEBAR #1: How many comets are there? Scientists estimate a trillion! Where are they? In the Oort cloud -- named after the astronomer who theorized it, a thick shell around our Sun that starts well beyond the orbit of Pluto, the outermost known planet, and extends almost two light years beyond, half way to the nearest star. This is the incubator of comets, where they travel amongst one another in a vast, dark orbit, knocking each other about, absorbing dust and gas as they pass. For a comet to fall from its wanderings in these nether regions down to Earth's orbit takes about a million years. Another comet belt closer to home is the Kuiper Belt, where a 120-mile wide iceball called Chiron dwells in the region between Saturn and Uranus. Nobody knows how many icebergs exist in this belt of sky.
SIDEBAR #2: Did an asteroid or comet extinguish the dinosaurs and more? The smoking gun, so to speak, is a crater six miles wide in southern Mexico's Yucatan. Some massive thing impacted that place about 65 million years ago, and the resulting dust and fires killed the dinosaurs and 90 percent of all species on our planet. In November 1996, a meteor struck western Honduras excavating a 165-foot crater and destroying acres of coffee plantations. Had it struck ten hours later, Manila or Bangkok would have been totally destroyed. We're bombarded with tons of cosmic dust every day; just run your finger across any bookshelf and you'll pick up a few bits of powder left by colliding asteroids. A fist sized meteor survives the journey to earth about every two hours! Thousands of Americans saw a meteor streak across the sky above a football game the evening of October 9, 1992, and a 28 pound chuck of cosmic debris, still warm to the touch, smashed the fender of a Chevy Malibu nearby (a collector bought the meteorite for $59,000 and the Malibu for another $10,000).