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The California Literary Review asked me to answer some questions pertaining to Chapter 1 of my book, Death from the Skies!, where I talk about asteroid impacts. They’ve posted my replies on their site.
This is such a broad and interesting topic, and it’s really hard to boil down the important stuff to just a few dozen words. I tend to be a bit, um, wordy, so sometimes I have a hard time saying my name in a few dozen words, but I hope that the Q&A gives you a sense of what’s going on.
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The original BA site (with the Moon Hoax debunking, movie reviews, and all that) can be found here.
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December 2nd, 2008 at 4:06 pm
Other reporters have also inquired.
Greetings, Mr. Plait;
My name is Mark LaFlamme. I’m a crime reporter and columnist at the Sun Journal in Lewiston, Maine. Lately, I’ve been writing cover stories for our hip and happening B Section, which runs on Sundays. For no good reason, I’ve decided to write about the threat of asteroid strikes as a feature for the end of November. I’m sort of a hack astronomy buff and asteroids are my current obsession.
I subscribe to Bad Astronomy and so clearly, I’m very familiar with your book “Death from the Skies.” I thought it would be enlightening for my readers (and beneficial to your book promotion efforts) to get a few words from you on the subject. I won’t be writing anything heavy on science so my questions will be light. In fact, I’d be content if you ignored my questions altogether and went in your own direction. I am nothing if not easy.
If you’re interested in some easy book promo, let me know and I’ll fire off some questions for you. God willing, we’ll survive long enough to get in a decent interview. I don’t trust that shifty Apophis to stay on schedule at all.
Thanks. I hope to hear from you.
Mark LaFlamme
Lewiston, Maine
mlaflamme@sunjournal.com
http://www.marklaflamme.com
December 2nd, 2008 at 4:12 pm
[...] do global damage would be big enough and bright enough to spot a long time in advance. (Cited in BA Blog: What if a large asteroid were on its way in?) __________________ 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 [...]
December 2nd, 2008 at 4:26 pm
The story about when to do what (and who’s gonna make the decision) is vastly more complicated than the interview suggests – just look at the proposals made in this recent report to the United Nations. Which still leaves the crucial questions basically unanswered, esp. regarding the threshold between doing nothing and doing a lot (namely launching a nuke into space).
December 2nd, 2008 at 4:27 pm
I’ll get the obligatory Bruce Willis reference out of the way now so we can move on to more constructive commenting.
December 2nd, 2008 at 4:38 pm
if big chunks hitting us is whatever small a risk, are there any official statements by re-insurance companies how they deal with that kind of risk?
December 2nd, 2008 at 4:47 pm
Lewiston!? Don’t answer him Dr. Plait, I escaped from Maine. Mr LeFlamme is really a black bear, and he’ll steal your blueberries! (Sorry, I couldn’t resist being a little extra goofy there!)
After 2029, let’s see what sort of excitement a 1 in 45,000 chance generates for 2036.
December 2nd, 2008 at 4:54 pm
Lewiston is a city by Maine standards (which of course means it actually has traffic lights). I happen to live in the last town in the whole US with a crank telephone system, they only modernized in the mid-80s. The fact I can even get an internet connection here is amazing.
Can’t beat Maine though for being pretty and wonderful lack of light pollution to see the sky.
December 2nd, 2008 at 4:55 pm
Ok what does that make a New Brunswicker like me?
December 2nd, 2008 at 5:01 pm
Uhhh … Canadian?
December 2nd, 2008 at 5:02 pm
That is the province not the city in New Jersey. Noadi the skies are diffently better around here then most other places.
December 2nd, 2008 at 5:04 pm
@Brain it just sounded like we were all primitives around here.
Sorry to everyone else, just had a couple of minor shocks tonight.
December 2nd, 2008 at 5:11 pm
chance of dying by asteroid strike is 1 in 700,000? About the same as dying in an amusement park ride? We should have several people worldwide dying in asteroid impacts per year! Where are these asteroid strike deaths?
December 2nd, 2008 at 5:52 pm
On another thread on this subject, I had posted an embedded (Japanese) video simulation of a giant asteroid impact on Earth. Click on my name and the link will direct you to it, if you’re interested.
December 2nd, 2008 at 6:35 pm
Cormac McCarthy’s novel The Road portrays the aftermath of an asteroid impact. I highly recommend it.
December 2nd, 2008 at 7:23 pm
I used to live in a little town in Maine called Owl’s Head. Hence why I was being a bit silly with Mr. LaFlamme.
Once I took my wife to visit the folks up there over the holidays, and she was amazed at the sky on a crisp winter’s night (of course she’s a city girl, so seeing stars was a rarity for her!).
callmeclint, as I recall, McCarthy never really specifies the cause of the disaster. I too think it was an asteroid, but there are numerous debates about the subject. And yes, it’s a pretty cool book.
December 2nd, 2008 at 7:23 pm
The only black bears who come to Lewiston are the crack addicted ones. It’s very sad.
Anyway, I’m going with Dr. Julie Ziffer for the sure Pulitzer-winning asteroid piece. A foremost expert on the topic and one with great class and media sense.
December 2nd, 2008 at 7:26 pm
Owl’s Head is very nice. The kind of place to which people from Lewiston book vacations, if they can stay off the crack rock long enough. Have I mentioned we’re filthy with crack?
“The Road” is amazing. Very noir.
http://www.amazon.com/Road-Movie-Tie-Cormac-Mccarthy/dp/0307472124/ref=sr_1_1?ie=UTF8&s=books&qid=1228271103&sr=1-1
December 2nd, 2008 at 10:51 pm
Phil, the science section of the New York Times has some reporting on some early Earth studies, which are showing that the Late Heavy Bombardment, which put all the mare basins on the Moon, may not have made much of a splash (groan) in the Terrestrial biosphere. In short, there is no evidence that Earth’s oceans disappeared during that time.
http://www.nytimes.com/2008/12/02/science/02eart.html
December 3rd, 2008 at 1:03 am
Blaise Pascal, I think you’re confusing frequency of an event with its average death rate. You may hear every year of one dying in an amusement park, but most likely you will never in your lifetime hear of a single event with 1000 casualties, happening every 1000 years. But still, both scenarios represent the same death rate. Human intuition is quite bad at accurately assessing risk.
December 3rd, 2008 at 1:47 am
1 in 700,000 odds are because an asteroid strike has the potential to kill EVERYONE on the planet at the same time. If one such strike occurred once every 700,000 lifetimes (which is around 50-60 million years) then each person who lived during all those millions of years would have, on average, a 1 in 700,000 chance of dying because of it.
To be honest, though, I think the odds of being killed by an asteroid, at least a sizeable one we can see coming, are zero. I think that we are at the technological level that if we did see one coming that is still twenty years off, we would get off our backsides and actually get the job done. Since that threat really is upon us yet, we don’t feel like we have to be so proactive.
December 3rd, 2008 at 2:53 am
On the Tunguska-event asteroid:
“So this is a threat astronomers take pretty seriously… even if something this big only hits us on average every few centuries.”
Here’s what I’ve been wondering about that: assuming asteroids of this size hit us every couple of centuries, can you give us some other examples? Even taking into account that most of these would hit in remote areas or the sea, wouldn’t there be geographical evidence at the very least? Like relatively recent craters? These things are big enough to leave a significant mark, aren’t they?
December 3rd, 2008 at 5:42 am
Arik Rice, I admire your faith in humanity’s ability to overcome bureaucracy and nationalism.
December 3rd, 2008 at 8:09 am
Arik,
I’m not so sure about that — Phil addresses the issues involved in deflecting/blowing up/etc. an incoming projectile and it’s not about the technological level… the laws of physics don’t care about technology…
nonetheless, I’d like to think we could figure something out if someone yelled “incoming!”
December 3rd, 2008 at 8:16 am
Arik (cool name by the way)- I don’t think you can say the odds are “zero”. We just had a pretty big one smack into the skies above Canada the other day (yes, I know it didn’t cause any damage and was basically just cool- but if it was 10 or 100 times bigger….).
Also, maybe we are pretty good about tracking asteroids from the main belt. But I’d be a little more worried about some rogue comet that could come screaming in from deep space.
Since either a comet or an asteroid could (potentially) be an extinction level event I’m totally baffled by the fact that we don’t have an internationally funded and coordinated program in place to track these objects. But we do now have beer that was made from wheat that was grown on the ISS so I think we can have a relax over it (couldn’t resist another jab at the ISS- don’t get me going on the spider experiment up there).
December 3rd, 2008 at 9:30 am
“Here’s what I’ve been wondering about that: assuming asteroids of this size hit us every couple of centuries, can you give us some other examples? Even taking into account that most of these would hit in remote areas or the sea, wouldn’t there be geographical evidence at the very least? Like relatively recent craters? These things are big enough to leave a significant mark, aren’t they?”
Arizona was hit 20000-50000 years ago, leaving a 1200 meter wide crater. The chunk that hit there is only believed to be an 80ft rock. Still, if something like that were to hit a populated area, it would be a major disaster.
Speculations are also going into a hypothesis that the Indian Ocean was hit 5000 years ago. Traces of a huge tsunami in both Madagascar and Australia points to such an event, but it is still disputed.
I can’t think of any other recent events of that scale, but I wonder how many traces we would find of a Tunguska-like event if it happened in a remote area even a few century’s ago?! If it exploded in the air over e.g. the Himalayas, Antarctica or other areas where you wouldn’t find remnants of fallen trees, it would be hard to tell anything had happened without actively looking for it.
December 3rd, 2008 at 10:52 am
@Job “Here’s what I’ve been wondering about that: assuming asteroids of this size hit us every couple of centuries, can you give us some other examples? Even taking into account that most of these would hit in remote areas or the sea, wouldn’t there be geographical evidence at the very least?”
There is an 18-mile wide crater at the bottom of the Indian Ocean called Burckle crater. According to some researchers it was created by an asteroid impact only 4,800 years ago.
http://www.iht.com/articles/2006/11/14/healthscience/web.1114meteor.php?page=1
If such an impact were to happen today it might kill 250 million people and cause a tsunami wave 50 meters high out to a distance of almost 5,000 kilometers.
***************************************************************************
Burckle crater in the Indian Ocean
Age = 4,800 years
Latitude = 30.865 deg S
Longitude = 61.365 deg E
Width = 18 miles = 29 km
Depth of ocean = 12,500 feet = 3,810 meters
Target planet or moon = Earth
Diameter of the impactor = 900.0 meters
Density of the impactor = 7.80 gm/cm^3
Initial velocity of the impactor = 50.00 km/sec
Initial elevation angle of the impactor above horizon = 90.0 degrees
Density of the target surface = 1.00 gm/cm^3
Ocean strike: depth of water = 3810.0 meters
Distance of observer from surface impact point = 1000.0 km
Gravitational acceleration at surface of planet = 9.81 m/s^2
Minimum velocity of an impactor = 11.2 km/sec
Maximum velocity of an impactor = 71.9 km/sec
Atmospheric pressure at surface = 1.013E5 pascals
Atmospheric density at surface = 1.226E-3 gm/cm^3
Surface temperature = 15.0 deg C
Atmospheric scale height (isothermal) = 8.43 km
Initial kinetic energy of impactor in outer space =
3.72E21 joules = 8.89E5 Megatons TNT
An impact of this size occurs once every 3.37E5 years
Atmospheric entry:
Velocity of the impactor at the surface = 49.91 km/sec
Elevation angle of the impactor at the surface = 90.0 degrees
Amount of energy dissipated in the atmosphere = 0.38%
Duration of the atmospheric entry = 1.69 sec
Kinetic energy of impactor at the surface =
3.71E21 joules = 8.86E5 Megatons TNT
Ocean entry:
Velocity of the impactor at bottom of ocean = 32.09 km/sec
Elevation angle of the impactor at bottom of ocean = 90.0 degrees
Amount of energy dissipated in the ocean = 51.05%
Duration of the ocean passage = 0.10 sec
Kinetic energy of impactor at bottom of the ocean =
1.53E21 joules = 3.66E5 Megatons TNT = 8.25 Richter scale
Cratering effects:
Width of transient crater at bottom of ocean = 1.94E1 km
Depth of transient crater at bottom of ocean = 6.85E0 km
Volume of transient crater at bottom of ocean = 1.01E3 km^3
Width of final crater at bottom of ocean = 2.87E1 km
Depth of final crater at bottom of ocean = 1.09E0 km
Volume of final crater at bottom of ocean = 3.53E2 km^3
Thermal effects:
The fireball cannot be seen by the observer
Radius of the fireball generated by the impact = 3.10E1 km
Maximum distance that fireball can be seen = 6.27E2 km
Time for thermal radiation to reach its peak = 6.20E-1 sec
Duration of the thermal radiation = 4.02E2 sec
Distance out to which 1st degree burns happen = 522.0 km
Distance out to which 2nd degree burns happen = 475.0 km
Distance out to which 3rd degree burns happen = 429.0 km
Seismic effects:
Magnitude of ground shaking experienced by observer = 3.19 Richter scale
Time for the seismic waves to reach the observer = 2.00E2 sec
Observer’s experience: Shaking noticeably felt by people who are indoors
Distance out to which everyone feels ground shaking = 488.0 km
Distance out to which buildings partially collapse = 175.0 km
Distance out to which most private houses collapse = 43.0 km
Distance out to which most buildings collapse = 1.0 km
Air blast effects:
Peak overpressure of blast wave at the observer point =
8.20E3 pascals = 8.09E-2 atm
Time for the air blast wave to reach the observer = 2.94E3 sec
Peak wind velocity at the observer point =
1.90E1 m/s = 6.84E1 km/hr
Observer’s experience: Glass windows shatter
Distance out to which glass windows shatter = 1127.0 km
Distance out to which wood-framed houses collapse = 482.0 km
Distance out to which steel-framed buildings collapse = 149.0 km
Distance out to which highway girder bridges collapse = 128.0 km
Tsunami effects:
Inner diameter of initial cavity in the ocean = 3.77E1 km
Outer diameter of initial cavity in the ocean = 5.33E1 km
Depth of initial cavity in the ocean = 1.26E1 km
Wavelength of the peak amplitude = 3.98E1 km
Maximum height of tsunami at obs. without shoaling = 7.52E1 meters
Maximum height of tsunami at obs. with shoaling = 2.26E2 meters
Velocity of the tsunami for its maximum amplitude =
1.83E2 m/s = 6.58E2 km/hr
Period of the peak amplitude = 3.63E0 min
Time for the tsunami to reach the observer = 9.12E1 min
Distance out to which tsunami is 2 meters high = 20015.0 km
Distance out to which tsunami is 5 meters high = 20015.0 km
Distance out to which tsunami is 10 meters high = 20015.0 km
Distance out to which tsunami is 20 meters high = 11955.0 km
Distance out to which tsunami is 50 meters high = 4698.0 km
Distance out to which tsunami is 100 meters high = 2313.0 km
Estimated human death toll:
Estimated non-tsunami death radius = 482.0 km
Estimated tsunami death radius = 11955.0 km
Population density = Australia avg : number of deaths = 1.45E7
Population density = Russia avg: number of deaths = 4.67E7
Population density = USA avg: number of deaths = 1.72E8
Population density = World avg: number of deaths = 2.49E8
Population density = China avg: number of deaths = 7.68E8
Population density = UK avg: number of deaths = 1.37E9
Population density = India avg: number of deaths = 1.87E9
Population density = Bangladesh avg: number of deaths = 5.81E9
Percent of deaths caused by cratering effects = 0.00%
Percent of deaths caused by thermal effects = 9.39%
Percent of deaths caused by seismic effects = 0.09%
Percent of deaths caused by air blast effects = 11.85%
Percent of deaths caused by tsunami effects = 78.67%
December 3rd, 2008 at 11:06 am
One potential additional risk of a Tunguska size object, if it hit over a major city in a volatile political region, would be the impactor being mistaken for a nuclear strike, since the detonations will be of equivalent energy levels, and this setting off a nuclear confrontation, if cooler heads fail to prevail over itchy trigger fingers.
December 3rd, 2008 at 12:24 pm
@BA “Right now the chances are really low. Your personal odds of dying in an asteroid impact over your lifetime are about 1 in 700,000 – you’re just about as likely to die in an amusement park accident.”
As I’ve shown in a previous post, that 1 in 700,000 figure is pretty iffy. It depends on many different parameters that are assumed such as the maximum size of the impactor, etc. Changing some of those parameters can give you figures as low as 1 in 15,000. So I wouldn’t put too much stock into that number.
@BA “If there isn’t, we may have to launch a rocket at the thing and simply smash into it – the energy of impact is actually far larger than the detonation of a nuclear weapon.”
Hmmm, that one made my eyes open a bit. I’m pretty sure that’s an incorrect statement but let’s see. Let’s assume you have some type of rocket with a mass similar to an Apollo command, service, and lunar module which was roughly 100,000 lbs (45,000 kg). Let’s assume it impacts the asteroid with a relative velocity of 30 km/sec (30,000 m/s). That’s a kinetic energy of 2.0E13 (20 trillion) joules.
1 kiloton of TNT = 1.0E12 calories = 4.184E12 joules
So the impact energy is about 4.8 kilotons TNT which roughly one third the yield of the Hiroshima bomb of 1945 and about 1.5 percent the yield of a modern nuclear warhead (e.g., W78 warhead of the Minuteman III ICBM) and 0.01 percent the yield of the largest nuclear weapon ever tested (the 50 Megaton Tsar Bomba detonated by the Soviet Union on October 30, 1961).
So unless the mass of the impacting rocket is much larger than the Apollo payload I’m going to have to call BUSTED on that statement.
December 3rd, 2008 at 12:42 pm
Logic clearly dictates that sufficient force, applied for sufficient time, will cause any object to deviate its course.
Since time appears to be afforded to us, this simply leaves force to consider, both ensuring it is sufficient, and how it is applied.
About that…has anyone thought of using the energy in that big bright thing in the sky to help us?
Oh, and as he hasn’t been mentioned for a while… Bruce Willis.
December 3rd, 2008 at 12:49 pm
@Lazze “Speculations are also going into a hypothesis that the Indian Ocean was hit 5000 years ago. Traces of a huge tsunami in both Madagascar and Australia points to such an event, but it is still disputed.”
Slight correction. The chevrons found in Madagascar and Australia are from different impact events. The Madagascar chevron is thought to be related to the Burckle crater event of ~2,800 BCE. The Australian chevrons are from a different impact in the Gulf of Carpentaria that happened in 536 CE. Apparently there is some historical record of this second event – the Byzantine historian Procopius reported that the “sun gave forth its light without brightness” for the years 536 and 537 CE.
December 3rd, 2008 at 1:40 pm
@BA “Right now the chances are really low. Your personal odds of dying in an asteroid impact over your lifetime are about 1 in 700,000 – you’re just about as likely to die in an amusement park accident.”
David Morrison, who is really the acknowledged expert in this area, came up with a different number:
http://www.georgehoward.net/htmlfiles/David%20Morrison.htm
“Earth today in terms of probable casualties, noting in particular the existence of a threshold at about one million megatons of energy (corresponding to a two-kilometer asteroid) at which the global climate is severely affected and everyone is at risk, independent of proximity to the impact. One conclusion of such studies is that the statistical risk is greatest for impacts near the global threshold, amounting to an average risk of death for each individual on Earth of nearly one in a million per year, comparable to the risk of other more frequent (but less catastrophic) events such as earthquakes, severe storms, and volcanic eruptions.”
So Morrison’s risk of death per individual per year is 1 in 1,000,000. If you assume an average lifetime of 70 years then that’s a probability of 1 in 14,000 per individual per lifetime. This is roughly the same as my previous calculations in a previous post which assumed a maximum impactor size of some 10-20 km. So Morrison’s number is some 50 times more risky than the 1 in 700,000 amusement park accident rate being cited. He says that the risk is comparable to other natural disasters such as earthquakes and volcanoes. But unlike those other risks this one is potentially preventable which leads me to conclude that we should be spending at least some of NASA’s budget on this issue. How much? I’d vote for about 10 percent.
December 3rd, 2008 at 2:39 pm
@Tom & Lazze: Thanks!
So it’s actually closer to once every millennium or so than to once every couple of centuries?
December 3rd, 2008 at 3:47 pm
@Job “So it’s actually closer to once every millennium or so than to once every couple of centuries?”
It all depends on the size. Size matters. From what I’ve been able to gather the standard view on recurrence interval (time between impacts of a given size) from the Morrison, et al crowd is something like:
T-recur = (D / 4) ^ 2.35
T-recur is recurrence time in years
D is diameter of asteroid in meters
So let’s say you let D = 100 meters to represent an asteroid that can cause serious damage. So T-recur = 1,900 years.
I take it that some “radicals” in the Holocene Working Group think that number 4 should be replaced with something like 10. So a 100-meter impact happens much more often than once every 1,900 years, say once every 220 years.