Earth impact

bozo the clown

Is it true I have more chance of expiring from a global cotastrophe in the next 50 years as a result of a terestrial object from outer space colliding with Earth than winning the powerball with a $1 ticket.

Chronos

The odds are favorable. Catastrophic global events [according to geologists] only occur about one time every 50-100 million years. Keep buying those lotto tickets.

Phobos

actually...

1 YEAR PROBABILITY FOR ALL AMERICANS...

1 in 5,200,000 - - win Megabucks (1 play) (Massachusetts Lottery Commission, 2001)
1 in 600,000 - - 1 km asteroid or larger hits Earth – causes global havoc & kills billions (reported in Scientific American Nov 2003)
1 in 100,000 - - win Megabucks (play once a week) (M.L.C.)
1 in 5,000 - - small asteroid destroys a city/causes major tsunami (Sci. Am.)

city-destroying asteroids hit once every 200-300 years...the last one was in 1908 (Tunguska) which fortunately hit in a remote region of Siberia

the impact magnitude that Chronos mentions (like the K-T event) does occur once every 100 million years, but it take a lot less than that to cause a global catastrophe

selfAdjoint

In recent years I haven't had much respect for Scientific American, these silly probabilities lower it still more. 1 in 600,00 for a global catastophe asteroid hit means we should see something of that magnitude every 600,000 years, almost twice a megayear. At that rate the earth would be covered with big craters, erosion and mountain building wouldn't have had time to diguise them.

Phobos

Certainly the odds are tricky to calculate, but the order of magnitude matches other sources...

A September 2000 United Kingdom report on Potentially Hazardous Near Earth Objects says that a 1.7 km object hits the Earth once every 250,000 years. The results are:

Both land and ocean impacts raise enough dust to affect climate, freeze crops. Ocean impacts generate global scale tsunamis. Global destruction of ozone. Land impacts destroy area the size of a large state (California, France, Japan). A 30-km creater penetrates through all but the deepest ocean depths.

recently reported by Reuters...

If a massive near-Earth object measuring more than a kilometer (0.6 mile) in diameter slammed into the planet it would cause global devastation and kill an estimated quarter of the world's population. But scientists believe an event of that size would only occur about every 700,000 years

and from the Feb 2004 planetary defense conference in Orange County...

Asteroids capable of inflicting damage on a global scale hit the Earth roughly every million years...

This may be a biased source (from the UK government folks trying to study the asteroid threat), but interesting nonetheless...

Roughly speaking it seems that once every 100,000 years an object hits the earth of sufficient size to wipe out a quarter of life on Earth

Phobos

Quote by selfAdjoint

At that rate the earth would be covered with big craters, erosion and mountain building wouldn't have had time to diguise them.

any insights into this? (mountain building/erosion rates, number of visible craters now, etc.)

selfAdjoint

Well that's 5 KT level events in the last 3 million years (give or take 1 for distribution). Great 5 wipe outs of species, and still visible craters miles across, like Chixalub (sp?). I give you no recorded disaster like this to the Pleistocene fauna, and no such craters. Unless you say they all fell on the glaciers, so that "absence of evidence is not evidence of absence".

bozo the clown

ok there is no question that we do face risk from a major impact whether it be from small area destruction to widespread global destruction. The question is do we have the facilities to guage fair notice as to whether an object is going to collide with the Earth and can we ultimately prevent it from striking our planet.

Chronos

The chances of seeing it coming more than a week or so in advance are almost zero. The chance of us being able to do anything about it are about the same. Fortunately, the odds of it happening are pretty low. In the early solar system, calamity was a frequent occurence. These days, massive orbital bodies are pretty much set in their ways. Most collision courses have already ran their routes. We owe a big thanks to Jupiter for that.

Phobos

Quote by selfAdjoint

Well that's 5 KT level events in the last 3 million years (give or take 1 for distribution).

Ok, there's the confusion. The KT event was from a 10 km asteroid (or comet), not a 1 km asteroid. That UK report estimates the frequency of a 10 km object impact more on the order of once every 100 million years.

Phobos

Quote by bozo the clown

ok there is no question that we do face risk from a major impact whether it be from small area destruction to widespread global destruction. The question is do we have the facilities to guage fair notice as to whether an object is going to collide with the Earth and can we ultimately prevent it from striking our planet.

As Chronos said, it's tough, but not impossible.

We have the technology to find the asteroids. Now we just need to devote the time & money to do so. We (humans) are spending a few million dollars per year looking for the larger (> 1 km) near-earth asteroids. Check recent news stories & you'll see that some scientists & politicians are asking for more funding on this.

We also have the technology to deflect asteroids...given enough lead time. If we detect an incoming object with 1 weeks notice, then forget it. Duck and cover. If we detect it with a few years notice, well then we have a chance.

bozo the clown

oh dear its as bad as that huh

ok lets say an asteroid with say a diameter of 2km hit 'say for sakes of arguments' a sparse area in Arizona what effect would it have ?

Phobos

Quote by bozo the clown

oh dear its as bad as that huh

Well, it can get complex, but simply put, the more lead time, the better off we will be. Smaller objects require less lead time than more massive ones. And then there's the type of asteroid/comet...deflecting a solid rock has different challenges than deflecting a gravel heap.

But it's at least good news that astronomers are looking for near earth asteroids & comets and that NASA (and others) are investigating ways to deflect them. We may not be doing a lot, but at least we're not ignoring it. And the odds are low for anything hitting in the near-future, so we hopefully have plenty of time to deal with this.

ok lets say an asteroid with say a diameter of 2km hit 'say for sakes of arguments' a sparse area in Arizona what effect would it have ?

see my previous post (quoted text for a 1.7 km object impact)

Njorl

I'm sure if I won the lotto, I'd get hit with an asteroid the same day.

That reminds me of a joke:

Everyday a guy stops in his local church and prays, "Please God, let me win the lottery. Please, please PLEASE!"

After a year of this, with no results, the lights of the church dim, a heavenly beam of light falls upon him, and a booming voices states, "WOULD YOU AT LEAST MEET ME HALF-WAY AND BUY A DAMN TICKET!"

Njorl

Nereid

This site provides a good overview of the general issue (the only thing it doesn't really cover is the risks from 'new' comets), and has an up-to-date page with links to news items. Note that only one PHA is rated above zero on the Torino scale.

Chronos

I haven't won the lottery yet. So my guess is the odds are pretty good that the people who have are pretty safe for next few million years. The early solar system was a very violent place. Many collisions, moon formation and an unstable sun trying to reach thermal equilibrium. My best guess is we now live in a more stable system than the past. Most orbital bodies have found stable orbits and prefer to remain there. I would, however, like to see a timeline for crater formation on the moon to support that theory.

russ_watters

Quote by bozo the clown

oh dear its as bad as that huh

ok lets say an asteroid with say a diameter of 2km hit 'say for sakes of arguments' a sparse area in Arizona what effect would it have ?

HERE is an interesting site:

Your Inputs:
Distance from Impact: 500.00 km = 310.50 miles
Projectile Diameter: 2000.00 m = 6560.00 ft = 1.24 miles
Projectile Density: 8000 kg/m3
Impact Velocity: 10.00 km/s = 6.21 miles/s
Impact Angle: 45 degrees
Target Density: 2500 kg/m3
Target Type: Sedimentary Rock

Energy:
1.68 x 1021 Joules = 4.00 x 10^5 MegaTons TNT
The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 2.3 x 10^6 years

Crater Dimensions:
Final Crater Diameter: 29.61 km = 18.39 miles

Similar Threads for: Earth impact
Thread	Forum	Replies
Apophis to impact earth in 2036?	General Astronomy	54
did the core of the Earth collide with the Earth billions of years ago?	Earth	10
'Deep Impact' Impact...	General Astronomy	1
Earth almost put on impact alert	General Astronomy	12

bozo the clown	Earth impact Tweet Is it true I have more chance of expiring from a global cotastrophe in the next 50 years as a result of a terestrial object from outer space colliding with Earth than winning the powerball with a $1 ticket.

Chronos Recognitions: Gold Member Science Advisor	The odds are favorable. Catastrophic global events [according to geologists] only occur about one time every 50-100 million years. Keep buying those lotto tickets.

selfAdjoint Recognitions: Gold Member Staff Emeritus	Well that's 5 KT level events in the last 3 million years (give or take 1 for distribution). Great 5 wipe outs of species, and still visible craters miles across, like Chixalub (sp?). I give you no recorded disaster like this to the Pleistocene fauna, and no such craters. Unless you say they all fell on the glaciers, so that "absence of evidence is not evidence of absence".

Nereid Recognitions: Gold Member Science Advisor Staff Emeritus	This site provides a good overview of the general issue (the only thing it doesn't really cover is the risks from 'new' comets), and has an up-to-date page with links to news items. Note that only one PHA is rated above zero on the Torino scale.