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Asteroid Impacts Bigger Risk Than Thought
Rambo Tribble (1273454) writes "The B612 Foundation, a U.S.-based nuclear test monitoring group, has disclosed that their acoustic sensors show asteroid impacts to be much more common than previously thought. Between 2000 and 2013 their infrasound system detected 26 major explosions due to asteroid strikes. The impacts were gauged at energies of 1 to 600 kilotons, compared to 45 kilotons for 1945 Hiroshima bomb."
8/25/2000 (1-10 kilotons) NORTH PACIFIC OCEAN
4/23/2001 (1-10 kilotons) NORTH PACIFIC OCEAN
3/9/2002 (1-10 kilotons) NORTH PACIFIC OCEAN
8/9/2006 (1-10 kilotons) INDIAN OCEAN
9/2/2006 (1-10 kilotons) INDIAN OCEAN
10/2/2006 (1-10 kilotons) ARABIAN SEA
12/9/2006 (10-20 kilotons) EGYPT
9/22/2007 (1-10 kilotons) INDIAN OCEAN
12/26/2007 (1-10 kilotons) SOUTH PACIFIC OCEAN
10/7/2008 (1-10 kilotons) SUDAN
10/8/2009 (>20 kilotons) SOUTH SULAWESI, INDONESIA
9/3/2010 (10-20 kilotons) SOUTH PACIFIC OCEAN
12/25/2010 (1-10 kilotons) TASMAN SEA
4/22/2012 (1-10 kilotons) CALIFORNIA, USA
2/15/2013 (>20 kilotons) CHELYABINSK, OBLAST, RUSSIA
4/21/2013 (1-10 kilotons) SANTIAGO DEL ESTERO, ARGENTINA
4/30/2013 (10-20 kilotons) NORTH ATLANTIC OCEAN
yyeeeah, those are technically all between 1-600 kilotons.
Also, between 1 kiloton and 600 gigatons.
70% of the time over the ocean, 99.99% of the time over somewhere that isn't populated. It's a 1 in 10,000 occurrence that this happens over a populated area. Given a rate of 2 a year, that means once every 5000 years on average, and many of these will not do any damage. So I'd say this is pretty much pure hype.
Maybe some of those events were earthquakes. I find it hard to believe that their were 26 major impacts that we didn't know about. 600KT is hard to miss even if it is in a remote area.
About 3% of the planets land area is considered "urban". Taking into account the oceans that makes for right around 1% of the total surface area of the planet. That means that any given year there's about a 2% chance of an asteroid explosion happening over a major population area. That means a 1/3 chance of a significant (greater than 1 kiloton) explosion over an urban area over a 50 year time span. That's not crazy high, and most of those will occur at high altitudes, but it's certainly not once in 5000 years.
600 kilotons TNT is about 2.5e15 J. In comparison, the sunlight incident on the Earth is around 174 petawatts, meaning it takes roughly 20 milliseconds for that much solar energy to be absorbed (clouds, oceans and land masses) by the Earth (taking into account the ~30% reflected power). In comparison, the total world annual energy consumption is around 5e20 J. So, I wouldn't be too worried about added heat due to asteroids.
Sources:
https://www.google.com/search?...
http://en.wikipedia.org/wiki/O...
http://en.wikipedia.org/wiki/S...
Little Boy clocked in at ~15 kilotons, not 45 kilotons per TFS. Fat Man was ~21kilotons, though it was dropped off target and ended up doing less damage than Little Boy.
I want peace on earth and goodwill toward man.
We are the United States Government! We don't do that sort of thing.
Right - if we find out that these are happening much MORE often than previously thought, and yet damage is rare, then it seems like they're LESS of a risk than previously thought. Sort of like finding out that when you swim at the beach, sharks are close by more often than you realized - meaning the risk of them attacking you is lower. If anything this indicates that the Earth's natural asteroid defenses are more robust than previously realized.
Besides, I remember reading that kiloton-scale atmospheric asteroid detonations happened once every month or two, but this indicates it's less often than that, so they're actually LESS common than I thought. I could have misremembered that stat, though.
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Your math is off. If your numbers are correct, the risk of having at least one meteor over an urban area during those 50 years is:
P(N>1) = 1-P(N=0) = 1-(1-0.3*0.03)^100 = 60%
We don't have enough history to gauge what actually has happened over time, so we have to estimate.
We approximate by finding big rocks or chemistry on earth, looking at craters on the moon, or this.
In all these cases we are using the small but frequent to infer the distribution of big but hugely problematic events. Our best answer the question about the likelihood of a killer impact is grossly changed if this tail is changed.
Think about it like floods. We ask how likely a 10,000 year flood is going to happen next year. We have ~100 years of rainfall data. We fit it to a distribution that is appropriate and then use those fit parameters to make a best guess. If our rain gauge was only measuring half the rain, we might under-estimate the actual risk by a factor of 10x or 20x.
There is good correlation between "killer impacts" and location of the sun in the galaxy (yes it moves around). We are starting to enter a higher risk region (transition to edge of arm) and perhaps the fundamental distribution is changing. In that case the history of craters on the moon or other might not be meaningful indicator of the near future.
Considering this I think good tracking is not a bad idea and should be thought out well and properly considered.