Tunguska-Sized Asteroids Impacts Not So Common

JoeGee writes "MSNBC.com is reporting that a new study aided by data from U.S. Military satellites is causing scientists to revise the frequency of Tunguska-like impacts downward. Military satellites used to detect rocket launches and/or nuclear flashes are also good at monitoring the frequency of flashes in the atmosphere caused by ten meter to one meter sized objects burning up in our atmosphere. The study has concluded that Earth encounters much less interplanetary debris than was previously thought, and Tunguska-scale events only occur on average of once every millenium."

Comments

Variable

[Henry V .009]

This information is only as good as the time period we've been collecting it for. Meteor frequency is quite variable, therefore one decade's (or less) observation may not be of much value.

Let's just say...

[suprnova]

this is a good thing:

"Peiser said the study was valuable in another way because it helped show the U.S. military can detect the difference between a nuclear explosion and a meteor that sets off a flash similar to it -- a capability he said could help governments avoid mistaking a meteor blast for a nuclear weapon.

It would probably be good to have this capability to keep some guy with a key in a silo from pushing the panic button and obliterating us all....

Huh?

[Daniel Dvorkin]

So if I read the article right, what they're saying is that because only X meteors of a given size hit Earth in a given period, only Y meteors of a much bigger size will hit Earth in a much longer period? How do they know that Y has any relation at all to X?

Re:Huh?

[Merlin42]

My guess:
If you look out into space and a ratio(lets say L:B) of little asteroids to big asteroids and if you make the assumption that for an individual asteroid its size does not effect its chances of hitting a planet then:
X/Y=L/B => XB=YL => Y=XB/L
Now if you want to get fancy and remove the above assumption then it wouldn't be all that difficult to run a monte carlo simulation where you initialize a solar system with different populations of asteroids and apply the laws of gravity to simulate a few million years and use the output statistics to replace the above ratios. Hmmm maybe I should write up a grant proposal and see if anyone would pay for that cluster I've always wanted ;)

Re:Huh?

[fava]

|\
| \ Legend:
| \ \ = Observed meteor data (small sizes)
| \ or
F | \ Telescope observations (large sizes)
R | . . = Interpolated data
E | . * = Tunguska sized
Q | .
U | *
E | .
N | .
C | .
Y | \
| \
| \
+-----------------
0 S I Z E

According to the article there is a good coorilation between the
meteor data for the small sizes and the telescope observations
for the large sizes, therefore they assume that the graph is a
resonable model of the sizes of the interplanetary debris.
Therefore they feel that the interpolated data between the
two data sets is fairly accurate.

I cant believe that I am drawing ascii art graphs on slashdot.

I need to get out more. (Actually I am going to the premere of the
new Bond film this evening so I am getting out, just not enough)

Re:Huh?

[Daniel Dvorkin]

Okay, that actually helps a lot. I appreciate the effort you put into the ASCII art. Have fun at the Bond film. ;)

Re:Well....

[uncoveror]

We have very little to worry about from Asteroids, but we have a great deal to worry about from Space Invaders... ...what's the deal with all these asteroid stories? They are getting old.

Re:Well....

[einhverfr]

One possibility is that is was a loosely held together lump of gravel. This would have pancaked in the atmosphere and eventually exploded.

The problem is we don't know, and scientists are still debating it.

Bah!

[KillerBob]

Don't you read Spider Robinson? Tunguska wasn't caused by an asteroid, it was caused by Nikola Tesla's death ray device!

Based on hypothesis...

[Mazzaroth]

The conclusion of the analysis is valid if the following hypothesis (somewhat related, i know) are considered as true:

The rate of objects entering the atmosphere in the 10 years observation period is representative of the average rate of the 1000 years period of the conclusion

The rate is constant (no asteroids or comets storms like the Leonids shooting stars storm we just observed)

The sampling (300 meteors) is statistically significant

The extrapolation/interpolation to bigger size meteors is valid.

This is definitely not a sig.

Other Tunguska theories

[geoswan]

There are other Tunguska theories. One theory explaining the Tunguska explosion is that it was due to the release and subsequent explosion of a very large, high pressure, deposit of natural gas.

Proponents of this theory describe how near the very center of the explosion the trees were unburnt. They say that the gas squirted out from the underground deposit under such high pressure, over a number of days, that an ice dome formed around the hole -- just like your can of canned air gets cold. This ice protected the most central trees.

The explosion is said to be right over a natural gas field. The region of Siberia has huge natural gas reserves .