Phew! The above didn’t happen. 2012DA14 whizzed past. If all those overworked astro guys had instead made some rounding-off errors, it could very well have hit.
The amount of damage an asteroid impact might cause is directly proportional to the asteroid’s density, volume, velocity and the angle at which it strikes. While the mass, volume, density may vary, asteroid to asteroid, speeds normally are upwards of 25000kms per hour and the angle at which they enter our atmosphere is general 45˚. At lesser angles of incidence they might glance off back into space.
Anything that’s up to 40 meters across or, as NASA puts it on its website, “smaller than a modest office building,” would be incinerated by the atmosphere before it hit the ground. At most, its remains would produce a blast equivalent to three megatons — very bad news for anyone in the vicinity but not a cataclysm. Asteroids from 40 meters to 1 km across (2012DA14 is 80meters) could do tremendous damage but on a local scale, says NASA. A hit by a 2km or larger asteroid would cause a million-megaton blast and produce severe environmental damage on a global scale. The probable consequence would be an ‘impact winter’ with loss of crops worldwide and subsequent starvation and disease.
Everyone has read about the asteroid that impacted the earth at the Yucatan Peninsula near the Mexican town of Chicxulub, 65 million years back. It was estimated to be 10kms across and it left a crater 180 kms in diameter.
Imagine you were a herbivorous diplodocus spending a quiet afternoon with your girlfriend, a comely, plump brachiosaurus. You were thinking of sex of course but she roared she was hungry and so you both were merrily chomping away on the dense foliage at a spot where present day Chicxulub, Mexico, is. You munched, making Spielbergesque trumpeting sounds of pleasure at the salad you gobbled.
Those days the North American landmass looked different. It had a huge water body running right through it, splitting it into half. Africa was closer, real close. You could take an afternoon swim across the Atlantic Ocean to Africa, to say ‘yo’ to your cousin Bronto who’d moved there when the Cretaceous Age began. But I may be getting carried away. Chicxulub is roughly where the map below says ‘Gulf of Mexico’.
Here’s a graphic account of what might have happened….
If it fell on the day lit side, you’d probably not see the asteroid approaching against the bright sky. In daylight, it would become unavoidably noticeable eight to ten seconds before impact because it would then reach the upper atmosphere, and air trapped in front of it would be compressed to white heat. At 10 seconds before impact, it would appear eight times larger than the sun or moon. From that point onward it would grow to fill the sky and become millions of times brighter than the sun, as will be described.
If the asteroid approached on the night side of the earth, entirely in the earth’s shadow, it would not be visible until it hit the upper atmosphere, about 70 miles up. At 30,000 mph, it would cross those final 70 miles in 8.5 seconds.
Under local twilight conditions, a 10 km diameter object coming straight in should easily be visible with the naked eye at a distance of 15000kms, which would be tewnty minutes before impact. It would be small but visible. Two minutes before impact, at a thousand miles out, it would be the brightest thing in the twilight sky, almost as bright as the full moon.
A speed of 30,000 mph is 40 times the speed of sound and this means that air molecules in the path of the asteroid cannot possibly move laterally out of the way. Instead, the air gets compressed in front of it. The estimate for the temperature as a function of the kinetic energy of air moving at the asteroid’s speed is more than 50,000 ˚C, more than forty times the temperature of the Sun’s surface.
The final seconds
Regardless of the local time of day, when the asteroid is 30 miles out, anyone would see it as forty-five times larger than the sun. If you were standing near the point of impact, you’d feel ten million times as much radiation as comes from the sun. Combustibles on the earth will begin to smolder within a tenth of a second, and then explosively ignite, including trees, houses, clothes, and skin; even rocks would fracture because of the thermal loading. Nearly four seconds would still remain before “impact.”
“Impact” is in quotation marks because I am likening the impending collision as being between two solid objects, similar to a rock hitting another rock or some other hard surface. But the layer of 50,000˚C air in front of the asteroid would, in the eight seconds of atmospheric transit time, cause the asteroid’s rocky or metallic surface to melt and begin to boil and merge with the gaseous plasma state of the super-hot air. The situation on the ground would become similarly extreme in the final seconds.
In the final millisecond, all of the atmosphere that had been in the path of the asteroid would be compressed between it and what had been the earth’s solid surface. The density of the air would approach that of water. At one-tenth of a millisecond before the now hypothetical surfaces meet, the density of the air would be more than twice that of granite and approaching the density of iron. In the final microseconds before “impact,” the density of the trapped air would become equal to that of the adjacent materials and would soon far exceed the density of any ordinary substance as everything became a super-hot, high-pressure gas.
Then would come the “collision,” in which the asteroid merged with the matter of the earth.
The atmosphere would be pushed out of the way in the region of the impact and an atmospheric tsunami would radiate outward at an initial speed of thousands of miles per hour. The pressure wave would race across the continent at a slightly slower rate than the ground wave and acoustic waves in the earth. Within an hour, the shock waves would get to every part of the North American continent. The atmospheric pressure waves would sound to dinos like you like a rumble, on top of the rumble of the shaking earth and the rumble would rapidly increase to a blast of wind, followed by the first appearance of airborne dust. Debris falling in from space would arrive shortly.
Ground zero of the hit was over water for the Chicxulub meteor and it would cause a tsunami to radiate outward. The oceanic wave would trail the atmospheric pressure waves and your uncle Rex on the Eurasian landmass, who loved to shake but not stir other dinos with a booming,” I’m Rex, T-Rex”, would hear the rumble first, and then the disrupted ocean would begin surging inland as a two hundred foot high wave. Within a few hours at most, the main oceanic tsunami would arrive, well after the great blast of air and this time the wave height would be upwards of five hundred feet. Your uncle Rex would of course be history then. Sorry, prehistory.
Within maybe six hours, the whole would be jarred by the shock waves traveling through the core of the planet itself. Atmospheric shock waves would traverse the earth many times, reverberating as the hole that had been punched in the atmosphere by the asteroid filled back and forth in a swooshing oscillation that would decay over days back to equilibrium. For several days, secondary and tertiary shock waves and earthquakes would continue over the whole planet as previously pent up stresses at tectonic boundaries were released by the flexing of granitic continental and basaltic oceanic crusts.
Some ten-thousand cubic miles of continental rock and underlying mantle material from as deep as 50 miles would be blown into space by the impact. Rocks returning from space would be reheated in passing through the atmosphere. Slower settling, smaller pieces of dust and gravel would fall over the entire planet. The atmosphere would cloud up and block sunlight for several years, causing the earth’s surface to cool down while, at the same time, the low-albedo dust would collect solar energy and heat up, the temperature difference between air at altitude and near the surface resulting in intense winds and storms all over the earth.
Within the first few hours, the physical plant of life on the whole planet would be destroyed. You, my friend, and your plump, leaf-eating lady love with bad breath would kick it. So would your African cousin, Bronto.
And so it would remain that way for several years, the earth a huge orb,throbbing and smouldering, gasping for breath, until the atmosphere began to clear enough for the surface to begin to warm again. Plants would start coming out of cooling ground, and small animals would crawling out of the ruins of the former earth, into a new geologic age. Ironically, your sad demise would help the evolution of other creatures, among them smart Bengalis like me. Discovery Channel has a terrific must-see simulation of just such a cataclysm. Here it is…
There. I’m done. It’s not original of course. I’m no asteroid scientist. I filched it from the net and tried to inject some humor into it. Amen. But all this we have could end that way, suddenly, without warning as it has happened before on the earth. The evidence in the rocks is compelling.
Time Magazine’s Science correspondents, Jeffery Kluger and Nina Burleigh have written about a ‘Probability-of-impact grid’, called the Torino scale, which attempts to quantify the overall risk any one asteroid poses, on a graph with the risk from 0 to 100% on its x-axis and the size of the object on the y-axis. After objects are given a Torino score, they are ranked on a five-color chart, going from white (no hazard) to red (certain collision, capable of causing at least regional devastation of a kind seen only once every 10,000 to 100,000 years). And what is the Torino rating for 2012 DA 14, which will whiz by on Feb. 15? It’s a reassuring white — or no hazard at all.
According to Wikipedia, the Spaceguard Foundation (SGF) is a private, non-partisan, non-political and non-profit organization, dedicated to the study, discovery and tracking of Near Earth Objects (NEO) and protect the earth from the possible threat of impact. The foundation, established in Rome in 1996, is a chain of observatories engaging in NEO observations. It provides the observatories with services which would optimize the international coordination in NEO tracking. The individual observatories in the system participate in these services on a volunteer basis. All the observatories in the system are ground-based. Apollo astronaut Russell (Rusty) Schweickart’s B612 Foundation for Planetary Defense plans to launch a satellite telescope into the orbit of Venus to provide an eye in outer space for the Spaceguard Foundation.
In 1995, the US Congress, thanks in part to the efforts of Spaceguard and individuals like Schweickart, got NASA to take asteroids seriously. But the global financial situation and the fractious relations that exist between the countries of the world do not bode well for a coordinated response to NEO strikes. Designs for ingenious machines and methods to protect the planet, from nuking incoming NEOs to launching giant magnets to drag them off their orbits, are on paper, but have never been tested. One of the proposals at the last international conference of Planetary Defenders was a dual spacecraft kinetic impactor to nudge an incoming rock off course.
This month in Vienna, the Scientific and Technical Subcommittee of the U.N’s Committee on the Peaceful Uses of Outer Space will finalize formal recommendations on international asteroid defense coordination. The recommendations go before the full UN General Assembly this fall.
Schweickart has been pushing for such a plan at the U.N. for years. But he told TIME he doesn’t think most world leaders will pay attention until an actual object is incoming. “The first time a threat arises is the earliest time that most countries will become aware of the work we do, despite the fact that their representatives probably were part of the discussion process. Many, many issues will begin to be debated that should have been anticipated and simulated well ahead of time. It would not surprise me at all if this debating continues until it is too late to act.”
But you knew all this, didn’t you? Of course you did. I have really smart friends, all of them. Some very pretty but…sigh…unavailable. I have snatched most of the paragraphs above from Time, NASA and Wikipedia. The references to sex, the birds and the bees are all uncopyrighted.
The thingamaboid, 2012DA14, is estimated to be 80 meters across and if it hit, say Manitoba, it could wipe out the entire province, start raging fires and set off seismic tremors that could destroy all built-up structures there. I checked with the Lord. It’s not coming anywhere near Quebec, where I live. I could check with Sire if it’s coming your way, for a fee of course, which you can transfer into my Swiss bank account. Anyway, if you’re going to be squished, what do you need your money for?
Till now, I’ve never given a flying hoot about the possibility of being vaporized by a large asteroid. 2012DA14 makes me sit back, take stock, think, reminisce, pass wind. Ignore the last one. Anything can make me pass wind.
Anyway, in very general terms, I’m going to be nicer with Nurse Ratched (the boss lady who’s flatter than Saskatchewan). I shall utilize my middle finger only to scratch my head and scrape the insides of the depleted jam jar, not to waggle it saucily behind her departing back. I’m going to give my son, Andy, more frequent bear hugs and sit and watch his Mustang GT500 drifting car videos with him as many times as he wants. I might buy him the IPhone5 and a model airplane he has eyes on and all the RC cars he wants.
And then there are those scores of folk I have cocked a snook at over the years. I have taken the time to thumb my nose at them too. That’s just in case thumbing nose is not exactly the same as cocking snook. There were also myriads of others I’ve told off in my long and eventful life. As there are perfectly normal and probably nice folk that I have unfriended on facebook. And let’s not forget those others that I’d thought up some really mean and petty things to do to. I’d like to say to these folks how sorry I am.
Above all, I’m going to try to convince the Lord that I was only trying to look cool when I entered ‘agnostic’ in the religion field on my profile. Of course I believe in Him. He has given me my daily bread (though He could have done more, made it French Toast with mushrooms and coriander, if He wanted). He has forgiven me my trespasses, of which there have been many. I have been passing tres ever since I first learned that boys and girls were built differently.
(Of course, I take all my remorse back if 2012DA14 misses).
© 2012 Achyut Dutt.