Not really - but the REM lyrics seem fitting for this post.
During an earlier era, say 40 years ago when I was a teenager, no one even considered the kinds of existential threats we are aware of today – massive solar flares that could knock out the electrical grid for months on a continental scale, or extinction level asteroid impacts. Oh, science fiction authors of the time waxed poetic about such things (Larry Niven’s Hugo Award nominated 1976 novel “Lucifer’s Hammer” comes to mind) but most folks were more worried (me included) about finding themselves underneath an incoming Soviet ICBM warhead than an asteroid.
Last week two remarkable events came within 24 hours of each other. A small asteroid known as 2012 DA14 passed within 17,000 miles of Earth, closer to than geosynchronous communication satellite orbits (23,000 miles). Then there was the explosion of a meteor between 12 and 20 miles above Chelyabinsk, Russia. That these two events occurred within a day of each other is pure coincidence but also very extraordinary.
The Chelyabinsk event is referred to as a bolide, which is defined as an asteroid entering the atmosphere and exploding due to frictional heating and compression.
I have seen two bolides during my lifetime while sitting outside under a clear sky. The first time was in the late 80’s when I lived in Framingham, and the second was about 5 years ago, when I was on a Scout campout up in Bolton. Neither event was very big or made any sound, but was impressive to watch for the few seconds they were visible.
The Dinosaur Killer
Today, the idea that we could be hit by an asteroid is taken very seriously and the only reason we even know about 2012 DA14 is because astronomers have been actively looking for these things for the last couple of decades.
In addition, the only reason we are now looking for earth-crossing asteroids today is because of the 1980 publication of the then very controversial asteroid-impact dinosaur extinction hypothesis in the premier journal Science. It represented a paradigm shift in how we thought about extinction events and asteroid impacts. I still remember reading this article before my senior year in college and saying to myself . . . “Wow” (yes, I am a science nerd - so sue me). I ended up writing a paper on it for my planetary astronomy class that fall.
Shortly after the idea was first published, scientists referred to this hypothesis as the “KT Event” hypothesis, short for Cretaceous-Tertiary Asteroid Impact Extinction Event. Obviously, the shorthand version is easier to say three times fast.
It was only in 1990, when scientists determined that the previously identified 110-mile wide circular Chicxulub structure buried under the Yucatan Peninsula in Mexico was actually a 65-million year old impact crater that the KT Event hypothesis was accepted based on overwhelming geological, paleontological, and geophysical evidence. Work published as late as last week’s issue of Science again confirmed that the impact coincided with and spelled the demise of all dinosaur families other than birds (yes, birds are dinosaurs – think about that the next time you are filling the bird feeder, munching KFC or cursing Canada Goose poop).
The KT Event hypothesis (now theory) was a paradigm shift because now it was OK for scientists to talk about catastrophes in the geologic record and also to think that these events could also happen in the future . . . or now. The idea of geological catastrophes used to be denigrated in the scientific community . . . just like the idea of continental drift. It takes a lot to change a scientist’s mind – usually overwhelming evidence.
The realization that the Earth is still a target in a cosmic shooting gallery has led to the private and public funding of astronomical surveys of the inner solar system to find other potential “dinosaur killer” type asteroids. Astronomers, both professionals and amateurs, have found them by the hundreds and with advances in technology, the size of the asteroids being cataloged has gotten smaller and smaller. So far, nothing large has been identified as heading our way.
After last week’s event in Russia, something called the 1908 Tunguska Event also was discussed in the news. I wrote research paper about it while in graduate school in 1985 (yes, I still am a science nerd). Something exploded over Siberia in 1908 with a force now estimated at 10 plus megatons TNT equivalent which devastated an area of about 830 square miles or a circle with a diameter of 32 miles, about the distance between Westborough and Boston.
Although hypotheses on the causes of the event ranged from alien spaceships to miniature black holes, the evidence pointed to it being a small asteroid or comet slamming into the atmosphere at a speed in excess of 20,000 miles an hour and exploding, sort of like what happens when you throw a chunk of ice at a brick wall but a tad bit bigger. At the time I wrote the paper, scientists thought events of this size happened about once every 2,000 years and therefore would probably happen again. Those estimates have not changed.
Imagine how history would have changed if the Tunguska asteroid had exploded over Moscow, Paris, London or New York. Actually, it has been imagined, again by Sci-Fi writers (See S.M.Stirling’s “The Peshawar Lancers”), but I digress.
Planetary scientists are not surprised that last week’s Chelyabinsk Event also happened over the Eurasian continent. It’s the biggest land mass on the planet. The size this event is also remarkable. The power of the meteor’s explosion is now estimated to be in the range of 300 kilotons TNT equivalent although that estimate will most like change up or down as more data are collected. That’s 20 times the size of the Hiroshima A-bomb, which seems to be the yard stick to which all large explosions are measured these days.
This meteor came in to the atmosphere at a very shallow angle so atmospheric friction and pressure caused it to self-destruct long before it could hit the ground. I would imagine that if it came in more vertically, it would probably have hit the Earth, utterly destroying an area the size of downtown Boston. Yikes!
Put it into Perspective (fireworks, lightning and sharks oh my)
So, let’s put this into perspective. Your chances of getting killed by a shark are something like 1 in 3 million, yet look at what we did last summer off of Cape Cod, patrolling the waters, tagging sharks and closing beaches. Come on, who wants to be shark food?
Your chance of being killed by an asteroid impact are something like 1 in 200,000 – about 15 times greater than getting munched on by a shark.
According to the National Safety Council (NSC), you have a better chance of being killed by lightning (1 in 80,000) than an asteroid. Granted, it does NOT mean something like this couldn't happen tomorrow. It’s just more likely that you will be killed in a car accident (1 in 84) or by the flu (1 in 63) in the next year than by a meteor . . . or a shark. Interestingly, the NSC does say that your chance of death from fireworks is less likely (1 in 341,000) than being killed by a meteor.
I wonder if this means you can give your kids some M-80s next July 4th or send them into the water at Coast Guard Beach while the harbor seals are swimming around and not worry too much. Well . . . . Probably not.
We have over three times more people spread around the planet now than in 1908 so the actual likelihood of finding oneself underneath some sort of extraterrestrial rock is probably increasing with time. The need for finding asteroids long before they can hit the Earth is not ridiculous because today, we know what they can do and that they are out there whizzing around the solar system at speeds many times faster than a rifle bullet.
The technology for nudging them out of the way of the Earth already exists and it does not require Bruce Willis and an H-bomb (in fact, H-bombs would either be ineffective or only make things worse). We probably won’t find something the size of last week’s Russian meteor before it can do damage, but we are already able to find objects like 2012 DA14 and that was not true 25 years ago.
These are low probability events, but oh boy if they happen; the probability of having a lot of people’s day ruined is pretty high. Just talk to the people in Chelyabinsk.
Food for thought on a cold winter’s day (queue in the shark attack music from Jaws).