NASA announced this week that it has recalculated the number of PHAs – ‘Potentially Hazardous Asteroids’ for those of us who aren’t rocket scientists (your humble writer included!). Its earlier estimate of 2350 objects has been doubled, and now NASA says there are probably 4700 PHAs out there.
A PHA is an object larger than 110 yards/330 ft across, and which come dangerously close to the Earth from time to time. This size means that they would survive passing through the Earth’s atmosphere. Most objects (which are smaller than this) will burn harmlessly up, leaving nothing more than a brief flash in the sky for their passing, and perhaps a lump or two of space rock as is the case for most asteroids that collide with the earth at present. But these larger sized objects can be enormously destructive.
Look up the Tunguska meteorite which exploded over Siberia in 1908. This is believed to have been a few tens of yards (meters) across, and it is estimated to have had the explosive effect of a 10 – 15 megaton hydrogen bomb (1,000 times more powerful than the bomb dropped on Hiroshima).
So this count of 4700 potentially threatening objects out there starts off with objects three times larger than the Tunguska meteorite. What would the number be if objects down to ‘only’ the size of the Tunguska meteorite were included as well?
Due to various issues, it is not possible to predict with precision if or when any of these objects might strike the earth, due to their orbits being somewhat irregular, and the objects themselves changing in mass, for example, if a journey around the sun causes frozen gases to be melted and evaporated away. All NASA can say is these PHAs might, just possibly, hit the earth, and if one of them were to hit the earth, NASA says it would cause damage on ‘a regional or greater scale’.
There’s probably nothing we can do to protect ourselves from having an asteroid land fair and square on our head, any more than the witch could protect herself from Dorothy’s landing on her at the start of The Wizard of Oz.
However, those ‘regional or greater scale’ damages mean that the consequential effects of an asteroid threaten to be massively more than just a few squashed citizens. And we need to think beyond the immediate effect of the meteorite’s collision with the planet to the secondary and tertiary effects.
For example, if a meteorite landed in the ocean (and 70% of the earth is water, after all) that would be the primary event, and apart from a few bucket loads of fish and any nearby ships and submarines and planes, it wouldn’t be too big a deal.
But, wait. This would likely trigger an enormous tsunamis that would plunge much further inland than anything experienced so far, on countries all around the ‘rim’ of the body of water. This would be a devastating secondary effect for people in the path of the tsunami.
Keep waiting. We’re not done yet. How about the tertiary effect on people safely removed from the tsunami impact. We can’t even start to guess what the tertiary effects would be. However, in most countries around the world, both the population density and the level of industrial development is greatest around the oceans. So, for sure, there would be huge swathes of industry and agricultural production wiped out by the tsunami. Maybe a bunch of nuclear power stations would duplicate the problems in Japan after their 2011 earthquake and tsunami, and the fallout effects from that can travel for hundreds or even thousands of miles.
There’s another thing that tends to be close to the coast as well. Oil refineries. As this article is being written, most of the west coast of the US is seeing their cost of gas escalating, even though the price of gas is dropping around the rest of the country, due to the unexpected closure due to fire of just one of the west coast refineries some months back. What happens if a tsunami wipes out a bunch of refineries, and the docks/wharves/rail lines to get raw crude to the refineries and finished products from the refineries and on to their consumers?
Alternatively, what say the primary event is the meteorite landing on a populated area inland somewhere? The secondary event is clearly the death of everyone within maybe 50 – 100 miles of the meteorite impact (depending on its size). A large-sized event could take out New York City, Washington DC, and everything in-between.
What about a tertiary event? Think of all the dust – much of it toxic and some of it radioactive too – that would be created by this impact. We sort of know about the toxicity of the World Trade Center buildings after the 9/11 event; how much worse would it be after an event thousands of times larger in scale?
All that dust would have a tangible impact on the world’s climate. Whether it precipitated a ‘nuclear winter’ or just a more vague ‘global climate change’ it would sure do something.
In all probability, an asteroid impact would be survivable by the planet as a whole (although it is thought by many that an asteroid impact massively altered the planet’s ecosystem so as to kill of the dinosaurs way back when). But in equal probability, some of our delicately balanced and finely stretched supply and support systems would be totally fractured, causing for breakdowns in unexpected things in unexpected ways. Read again the amazing story of how a fire in a small factory in a small town in Germany is now leading to a worldwide problem in auto manufacturing, and ask yourself how many other single points of failure with wide effect there might not be that would be impacted (perhaps even literally) if an asteroid hits the earth.
Modern life is a bit like a set of stacked dominos. It only takes one or two well placed shoves to knock many of the dominos over. It is hard to tell how many of our dominos would be toppled by a meteorite.
Depending on the nature of the asteroid strike, and depending on where you currently live would depend on if you were able to survive in place, or if you needed to move to your retreat and hunker down. However, we’d classify most asteroid strikes as probably being some type of Level 2 event.
We also don’t really know how much risk there is of a large meteorite colliding with the planet. Smaller ones do so all the time, usually unnoticed (I can relax out on the deck in the countryside and on average will see a ‘shooting star’ pass by once every 20 minutes if the sky is clear and dark). But a PHA? Hopefully not in our lifetimes, and not in the lifetimes of our children, either. But if one does collide, hopefully you’ll be prepared.