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Comment by carbon8 | Hacker News Reader

Two more good videos (high quality, trail/train detail, booms, etc):

http://www.youtube.com/watch?v=XDqYclzto7k

http://www.youtube.com/watch?v=0ozSq3yEm3g

Sonic boom followed in 2 minutes, so the altitude was in 30-40km range. That's damn impressive, with all the sharp shadows from the buildings ... damn.

Why do you suppose there would be two contrails?

Quoting Phil Plait's very early speculation (http://www.slate.com/blogs/bad_astronomy/2013/02/15/breaking...):

"It appears to split, so I’m guessing the main mass split there. That’s not surprising; it’s happened with previous falls (like Sikhote-Alin). That means they could have disintegrated at different times, so there may be multiple places where pieces could fall."

I wouldn't think they are contrails. One would expect them to mainly be smoke and dust from the disintegration/combustion/ablation during the descent.

By definition, they aren't "contrails". A "condensation trail" can only happen when something like an internal combustion engine injects water (or another compound that will condense) into the air.

A fast object compress the air in front of it reducing the amount of water that can be solved into it, so the excess of water condenses.

It's very visible in planes about to break the sound barrier. Look for Youtube videos. The cones are spectacular, but also notice how a trail is sometimes visible originating from the tips of the wings.

So you don't need to inject the water, but to extract it from the air compressing it. Anyway, I'd bet the meteor trails consist of vaporized matter from the meteor itself.

Edit: see this one at 0:20:

http://www.youtube.com/watch?v=gw9MjutMhLs

It's true you can get water condensation features from local pressure minima like in wingtip vortices. However, they are transient, because as soon as the air returns to ambient pressure the condensation goes away.

Well. If the meteorite was partially composed of water, which was then vaporised off during the atmospheric ablation, then it might indeed be partially contrail!

A pure water meteorite hitting the atmosphere would be contrails all the way; just not in the way we're used to.

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