[meteorite-list] Rock on the ground or not?

[Chris Peterson]

That's a difficult question to answer. The majority of meteorites come 
from meteors that are not terribly bright. But mag -4, while technically 
a fireball, isn't much of one, and is very common. It's fair to say that 
a -4 meteor is a candidate for meteorite production, but I don't know 
how to quantify that chance.

If the information you are providing is purely from your own 
observation, there's not enough information to make any estimates. From 
a single vantage point, the velocity and fall angle of the event are 
impossible to determine. It may have been heading nearly towards you, 
several hundred kilometers away, or it may have been dropping straight 
down 50 km away. There's no way to tell. Finally, from a single 
viewpoint you have no way of estimating where the actual fall might be. 
Even with many witnesses and camera views, it's usually not possible to 
narrow a fall zone to less than many square miles.

The meteors that are most likely to produce meteorites have some common 
characteristics. They are slow, usually less than 20 km/s (which is most 
likely in early evening meteors). Their entry angles are shallow, which 
provides lots of time to slow down while high in the atmosphere, before 
the air becomes so thick that a fast object can ablate rapidly ablate 
away, or fragment into small pieces that burn up.

Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


----- Original Message ----- 
From: "Lasse Lindh" <3l at comhem.se>
To: <meteorite-list at meteoritecentral.com>
Sent: Sunday, March 30, 2008 6:44 AM
Subject: [meteorite-list] Rock on the ground or not?


> Hi all
>
> If one sees a meteor fall with a brightness of -4 or brighter, it's 
> duration is +10 sec. What is the chances of finding a small rock where 
> it suppose to have landed? Is it big enough  considering the 
> brightness and length of fall. It needs to be said that the angle of 
> the fall was around 75-80 degrees, allmost straight down.
>
> Regards
>
> Lasse