[meteorite-list] let me just share this graph

From: mexicodoug <mexicodoug_at_meteoritecentral.com>
Date: Fri, 5 Oct 2007 19:44:36 -0500
Message-ID: <002d01c807b2$16abcc70$4001a8c0_at_MICASA>

Hi Herman,

Glad it could be helpful, and also would like to thank your for the always
positive comments and attitude you have on the list.

I prefer the graph I already posted, but I got a private email that it was a
nice graph, but...but one had to stand on their head to read it best. So
here is another version to save anyone from breaking their neck:

http://www.diogenite.com/Huanocollo2.gif

The original, which I prefer, is at http://www.diogenite.com/Huanocollo.gif

Let me try to give a little meaning to the graph in case there are any
casual readers interested. As mentioned the graph is specific to the
latitude of the new Peruvian fall in October, though quite reasonable as an
estimate in most other circumstances for many latitudes. It simply shows
the fraction of the mass of the atmosphere above (or between if you like)
any altitude between sea level and 25 kilometers height. The total mass of
the atmosphere is considered by considering all the mass up to 100
kilometers altitude.

So, by looking at the graph, you can see that 63.7% of the atmospheric mass
is above 3.8 Km, the altitude of the new fall. Actually on the graph it is
closer to 64%, as the elevation I used was from the Bolivian report which is
a little less than the 3.8 Km, in case anyone was wondering. (Note to
Sterling, the 62.1% I quoted before was actually didn't include the value of
the mass in the interval from 3.8Km to 4.0Km going upward due to a little
careless arithmetic on my part, so there is a minor bit more atmosphere to
go through to get to the 37XX meters of the fall elevation..)

Alternately, by looking at the graph, you could determine that:
between 15Km (12.9% atmosphere mass above) and 20Km (5.6% atmosphere mass
above) altitude, i.e., there is 7.3% of the atmosphere mass, and above that
only 5.6%. This is of special interest to meteoritists, as those are the
typical altitudes given for bolides when ablation ceases usually at 3Km per
second fall speed (plus of minus 1 Km/s). For a meteorite(oid) not to enter
free fall velocity, i.e., maintain a non-trivial portion of its cosmic
velocity, a vertical descent, entering at an angle like Peru's, a vertical
fall (and this was not vertical, causing the requirement to be higher) would
have to be something over 5 tons of basically surviving material. There is
one unknown, though, and that is relative velocity the meteoroid had with
Earth, though one would expect it to have been fairly low in order to reach
the ground.

Finally, the free fall velocity or a sphere that weighs 2 tons at the air
density (same used to make the graph) is between 0.345 Km/s to 0.385 Km/s.
That is slightly above the speed of sound which over there is about 0.325
Km/s. So we are at least 6% above Mach 1 in free fall for a two metric ton
sphere of denisty 3800 kg/m^3. That would be a nice baseline for some
scenarios as data is released.

For the impact to have been subsonic, for a sphere of that density, the main
mass would definitely have to weigh less than 1.4 metric tons when it
impacted (assuming a sphere: orientation can half or double this value).
That is less than one ton of TNT (popular way to measure explosions), the
crater looks like it could be as much as a 2-ton TNT size or so but better
an more bellical person comment on this. That would require an impactor
weighing in the 5 to 25 metric ton range, traveling over 0.6 Km/s, but I see
I am getting into something Sterling might want to comment on.

Hope this sets set some more bases for thought...it is not intended to limit
scenarios, though. Hope I've not made any mistakes as I am in sort of a
rush since today is Monze Day.

Best health, Doug




----- Original Message -----
From: <Metorman46 at aol.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Friday, October 05, 2007 12:35 PM
Subject: [meteorite-list] let me just share this graph


>
> Thanks Doug;
>
> This graph is very useful for future reference.Great job thanks for
> sharing.There is some very informative posts coming out of the carancas
> fall.What
> an event!Record breaking probably."Meteoritically speaking".Thanks to all
> posters on this event and the calculations involved.
>
> Best Regards;Herman Archer IMCA # 2770
>
>
>
>
>
>
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Received on Fri 05 Oct 2007 08:44:36 PM PDT