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Re: [Phys-L] Russian Meteor Contrail(s)



On 02/17/2013 06:52 PM, Chuck Britton wrote:
One of the (many) videos of the recent meteor hit clearly shows two parallel counter-rotating contrails.

To create a contrail - wouldn't the meteor have to contain water?
I'll assume that this (internal) water caused it to explode into two (major) pieces that were then counter-rotating to conserve L.

I don't see how humidity in the air (per se) could cause a (persistent) contrail.

Or am I overlooking something?

My #1 hypothesis is that trail was made of smoke ... not water vapor to any
significant degree.

One can easily hypothesize that the object was made primarily of stone, containing
silicon dioxide and various metal silicates. When it burns in the air, you wind
up with micron-size particles of silica and various metal oxides, with maybe a
few exotic nitrides thrown in. Small particles of almost any dielectric material
will look like white smoke (because that's what they are).

By way of contrast, wood smoke is often gray, brown, or black due to unburned
carbon, associated with a low-temperature flame. At temperatures of thousands
of degrees, I wouldn't expect to see a lot of unburned carbon ... and the object
might not have had much carbon to begin with.

My hypothesis says the object did not contain much water. This is supported by
the fact that the object must have been mechanically strong in order to stay
together as long as it did. Any object with internal water would have exploded
long before reaching the observed fireball stage. There could have been a small
amount of external superficial water, but that would have cooked off at an early
state without anybody noticing.

Conservation of momentum (angular or otherwise) is not relevant because of the
huge aerodynamic forces. Any odd-shape object is likely to spin one way or
the other. If it /doesn't/ spin, things get even more interesting, because
now it flies like a knuckleball, and all kinds of weird things can happen.
I've seen fireballs turn corners.