[meteorite-list] Meteorite from Jupiter-- uh, I mean TO Jupiter

[Chris Peterson]

Hola Doug-

My earlier response to Pete had numbers attached: a 50 g stone suggests a 30 
mm diameter and a terminal velocity of 50 m/s (I assumed a sea level fall). 
Not having viewed the stone in question, I simply assumed it was spherical, 
hence there was no speed range given. I'm happy to see we've arrived at 
about the same numbers- ain't math grand?

All the same, it is possible, albeit extremely rare, for a small object to 
arrive at the ground significantly above terminal velocity. However, such 
scenarios would seem pretty much to require the low altitude fragmentation 
of a much larger body, ala Sikhote-Alin. It's hard to imagine such an event 
could occur without attracting a good deal of attention, so I think we can 
pretty safely conclude (for reasons other than the obvious statistics) that 
an isolated fall of a 50 g meteorite, or even the somewhat larger 
Wethersfield falls, occurred at anything other than the expected terminal 
velocity.

Sterling commented that all falls are different. But really, I think they 
are actually quite similar in most cases; what is different are the last 
second dynamics dependent on just what they actually fall on.
Chris

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


----- Original Message ----- 
From: <MexicoDoug at aol.com>
To: <meteorite-list at meteoritecentral.com>
Sent: Thursday, June 22, 2006 1:26 AM
Subject: Re: [meteorite-list] Meteorite from Jupiter-- uh, I mean TO Jupiter


> Chris wrote:
>
> <<It is certainly possible to devise entry scenarios where  meteorites 
> have
> unusually large velocities.>>
>
> Hola Chris and Sterling,
>
> You guys need to attach more numbers to these arguments imo with 
> sensitivity
> analysis.  Concretely, that meteorite in Darren's  picture-considering its
> shape-would be going about 47m/s (105mph), and not less  than 40 m/s 
> (89mph) and
> not more than 60 m/s (134 mph).  The worst  case is the energy of a fast 
> ball
> in the company baseball league, though  likelyhood is half that.
>
> There are lots of ways to throw a fastball and bruise a grandma or loosen
> old plaster that your fingers can push through anyway.
>
> _http://six.pairlist.net/pipermail/meteorite-list/2004-March/139871.html_
> (http://six.pairlist.net/pipermail/meteorite-list/2004-March/139871.html)
>
> FYI here is a thread I posted to in Mar of 2004 on the subject of  speeds 
> of
> falling meteorites.  I don't think there is all that much  uncertainty to 
> the
> practical endpoints of how fast they can hit as terminal  velocity is 
> reached
> easily in virtually all these cases, (the latter which Chris  has 
> mentioned).
>
> I wouldn't hesitate to catch a baseball sized meteorite in the pocket of a
> baseball mit, though I am sure that that same falling rock would easily 
> break
> someone's arm.  People can karate chop wood in half with bare  hands and 
> the
> plaster of old homes can really be falling apart, how many of  us have put 
> our
> hands through the wall on ocassion, so I don't see anything odd  with the
> results.  People who get punched get bruised all the time,  heck, some 
> people get
> bruises on their butts from just sitting down.   Once the misconception is
> overcome that meteorites have retained cosmic  velocity it just becomes a
> question on how big the rock is and what it  hits.  An ordinary tale of 
> sticks and
> stones and bones.  I was  carrying an iron in the back of my pickup and 
> driving
> like a demon a while  back.  Didn't see a dip in the road and there was a 
> rock
> in the back of my  truck.  When the truck was back on all fours again, the
> rock was still at  zero g, and now I have this great crater to show for 
> it. They
> just don't  make the tinbed pickups like they used to...
>
> Here's the calculations if you want to go through them.  A bowling  ball
> sized chondrite (11.25cm radius) weighs less than 23 kg and falls at about 
> 291
> mph (130 m/s) (see prior post link provided above).  The terminal 
> velocity
> varies by the sqrt(mass)/sqrt(x-sectional area).  So for the  same 
> material in a
> sphere mass increases with r^3 but cross sectional area with  r^2.  The
> dependence reduces to simply velocity being proportional to the  square 
> root of the
> radius.  Thus a 50 gram sphere = 13.7 cc, r=1.49 cm  can fall at 36% of 
> the
> bowling ball which gives the 47 m/s ball park you're  all in.  In that 
> email I
> also checked the practical limits by  flattening it to a 
> shield(3.3):(3.3):1 and
> orienting it in a 3:1 length:diameter  ratio and found that  the terminal
> velocity range was 90-130-211  (m/s), in other words
> 69%(shield):100%(sphere):162%(oriented).  That's a  range of 1:2.35 from 
> slowest to fastest.  Without
> messing with the radicals  since it is late, if we apply the same factors 
> to the
> 50 gram piece, we see the  speed range to hit the guy who though he was 
> going
> fishing is 32.5 m/s (the  speed of a typical baseball fastball but only 
> 30% the
> energy) on the low end and  76 m/s (a major league record fastball's 
> energy)
> on the fast end.  The  energy difference is a theoretical factor of 5
> (76/32.5)^2.  But those are  the real extremes.  If we assume they are 
> representing a
> couple of sigma  deviation, everything like the one in Darren's picture is 
> in
> the  40 to 60 m/s range to bracket the 47 m/s. with reasonably a  double
> whammy packed in the fastest ones vs. slowest in this range.
>
> Even after taking into consideration reasonable altitudes (Colorado has a
> somewhat thinner atmosphere causing the retention of a bit higher 
> terminal
> velocity...for example, than say New Orleans, and that 10 mph  seabreeze, 
> the
> meteorite that hit that guy would have had a bit less than the  energy of 
> a
> company baseball league fastball's energy.  And if it hits old  plaster 
> will break
> some loose, and if it hits granny can break a bone and  definitely give a 
> black
> and blue mark.  But if it hits Steve, the Jensens  or several other burly
> collectors out there on the shoulder blade it might  actually feel good 
> even
> before they knew what hit them.
>
> Saludos, Doug