What caused the massive explosions in Russia?

[OmCheeto]

Not necessarily - it is a matter of distance from the explosion.

And I would imagine, duration. The meteor would have been dissipating energy the entire time, from entry, to disintegration. Does anyone know how far it traveled through the atmosphere?

hmmm...

from my calculations, this meteor arrived with a speed of 17.8 km/sec

Earthsky.org lists these numbers for various showers:

Leonids: 71 kilometers per second
Perseids: 61 kilometers per second
Orionids: 67 kilometers per second
Lyrids: 48 kilometers per second
Geminids: 35 kilometers per second
Fall Taurids: 30 kilometers per second
Delta Leonids: 23 kilometers per second
Draconids: 23 kilometers per second

ref

Bah! Lame! Slower than a Draconid!

 

[BobG]

Or put another way, it sounds like you think an unperturbed trajectory (again, of at least the last 10 million km) exists that can cause a below escape velocity impact and that most or all NEOs that hit us have such such a trajectory by definition of being NEOs. It doesn't make sense to me that you used the Earth sweeping out its NEOs as an example unless you think a significant fraction of them (all of them?) Impacted at below escape velocity.

Could you please try to answer more succinctly because all of the qualifiers you are putting on this don't add clarity and seem to contradict your examples.

If there's a lot of debris sharing the Earth's orbit (as there was early in the Solar System), then there's a lot of collisions. Low velocity impacts are still the exception, but there's still a lot of them.

You can't have an unperturbed trajectory. Both the asteroid and the Earth are orbiting the Sun and the Earth is perturbing the asteroid's orbit (and, likewise, the asteroid is just slightly perturbing the Earth's orbit).

To glance at the orbits of near Earth asteroids, you'd say a lot of them look pretty similar, but having a similar size isn't enough. They have to match other parameters as well. And they have to collide before their orbit is changed again.

 

[Solon]

Now that the large chunk of meteorite has been removed from the Chelyabinsk lake, I'm puzzled as to how it remained intact and also ended up 6 feet or so below the lake bed. I'm getting mixed results from different experts on meteorites as to the terminal velocity on impact with the water, anywhere from 100 to 600 miles per hour. !00 seems slow to me, 600 probably too high. The streamlined kinetic impact weapons will reach up to Mach 2 from 50,000 ft, 900 mph from 30,000 ft, so an irregular object must be at the lower end of the estimates it seems.

Using this calculator, with a "brick" drag coefficient, 600 Kg, and 1 meter cross section gives impact speed of 70 M/s. (150 mph, 230 ft/sec)
http://www.calctool.org/CALC/eng/aerospace/terminal
From info on the chunk:

"The rock crumbled into several chunks as scientists began lifting it from the ground with the help of levers and ropes."

Crumbled would suggest a relatively soft object, and that should not have survived impact. Could a much harder object, even at 100 mph, remain whole on initial contact? Water is incompressible and quite dense. It will stop a 50 caliber machine gun bullet in 5 feet or less of water, so how far could the meteorite have traveled before being stopped? How much energy would be dissipated? I'm stuck trying to form a complete, mechanically sound model of this work in my head, so hoping someone can put some numbers together that do make sense!

 

[Bandersnatch]

Now that the large chunk of meteorite has been removed from the Chelyabinsk lake, I'm puzzled as to how it remained intact and also ended up 6 feet or so below the lake bed. I'm getting mixed results from different experts on meteorites as to the terminal velocity on impact with the water, anywhere from 100 to 600 miles per hour. !00 seems slow to me, 600 probably too high. The streamlined kinetic impact weapons will reach up to Mach 2 from 50,000 ft, 900 mph from 30,000 ft, so an irregular object must be at the lower end of the estimates it seems.

Using this calculator, with a "brick" drag coefficient, 600 Kg, and 1 meter cross section gives impact speed of 70 M/s. (150 mph, 230 ft/sec)
http://www.calctool.org/CALC/eng/aerospace/terminal

Why do you think it was falling at terminal velocity? (hint: see post #101)

 

[Solon]

"Meteorites hit the ground at terminal velocity, about 200-400 miles per hour."

http://meteorites.wustl.edu/realities.htm

I thought that some of the forward velocity the meteorite carried from the meteor entering the atmosphere would have been added to the gravitational acceleration, but that's not the case, so I am informed.