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Possible meteorite hit?



 
 
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  #1  
Old December 22nd 08, 07:08 PM posted to sci.astro.amateur
George Normandin[_1_]
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Default Possible meteorite hit?

I just received an e-mail (11:30 am EST 12/22/08) from my friends at
Kopernik Observatory (www.kopernik.org) asking for help examining a possible
meteorite fall from a few hours ago. My question is: How do you tell a
meteorite from some other falling object? Other than checking for burn
evidence, magnetic and metallic properties and possible radioactivity, what
else should we check to determine what this "rock" is?



Here's want I know so far:



"We just got a call from emergency services in Port Crane, New York. He said
this morning a couple (names deleted) were eating breakfast and a loud crash
sent them to their garage, where they say a big rock had crashed thru the
window and made a hole in the concrete floor. The owner said the angle of
trajectory was such that it couldn't have come from Earth, and saw no
footprints or other signs nearby."

George N

  #2  
Old December 22nd 08, 07:53 PM posted to sci.astro.amateur
Chris L Peterson
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Default Possible meteorite hit?

On Mon, 22 Dec 2008 18:08:10 GMT, "George Normandin"
wrote:

I just received an e-mail (11:30 am EST 12/22/08) from my friends at
Kopernik Observatory (www.kopernik.org) asking for help examining a possible
meteorite fall from a few hours ago. My question is: How do you tell a
meteorite from some other falling object? Other than checking for burn
evidence, magnetic and metallic properties and possible radioactivity, what
else should we check to determine what this "rock" is?


There will be no burn evidence to the surroundings (because meteorites
fall cold). There is likely to be a fusion crust on the outer surface,
which is a black or dark brown glassy coating. The interior probably
looks something like concrete. If it damaged the concrete floor, some of
the fusion crust should be chipped away, exposing interior surfaces.
Here's an example of what a fresh fallen stony meteorite typically looks
like: http://www.cloudbait.com/science/bermet.html

Nearly all meteorites are stony. Most, but by no means all, contain
enough iron to be slightly magnetic. But that's not really diagnostic,
since many Earth rocks are magnetic as well. Unlike the case of Earth
rocks, the iron is usually in metallic form. So sanding smooth a bit of
exposed interior may reveal metallic flakes.

Meteorites are never radioactive (other than trace radioisotopes like
those found in all rocks).

Anybody with a little experience studying or collecting meteorites can
probably say with reasonable confidence if the object is a meteorite or
not. The only certain method is to have it analyzed, since meteorites
have distinctive mineralogical characteristics that are unambiguous.

"We just got a call from emergency services in Port Crane, New York. He said
this morning a couple (names deleted) were eating breakfast and a loud crash
sent them to their garage, where they say a big rock had crashed thru the
window and made a hole in the concrete floor. The owner said the angle of
trajectory was such that it couldn't have come from Earth, and saw no
footprints or other signs nearby."


Meteorites fall vertically, or nearly so. So I'd be a little concerned
about the observation that this object fell through a window. Meteorites
that strike structures fall through the roof. If this object came at a
substantial angle, with no possibility of having been deflected first,
it is unlikely to be a meteorite.
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
  #3  
Old December 22nd 08, 09:39 PM posted to sci.astro.amateur
Dave Typinski[_3_]
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Posts: 778
Default Possible meteorite hit?

"George Normandin" wrote:

Here's want I know so far:
"We just got a call from emergency services in Port Crane, New York. He said
this morning a couple (names deleted) were eating breakfast and a loud crash
sent them to their garage, where they say a big rock had crashed thru the
window and made a hole in the concrete floor.


Wait, what? A "hole," as in "it put a hole clean through a 4" thick
concrete slab"? What kind of Dirty Harry Callahan meteor is this?

Would a small meteor--even a hypothetically pure nickel-iron job--have
enough energy at terminal velocity to hole a residential garage slab?

Unless it was really big, it'd have reached terminal velocity before
it hit the ground: something less than 100 meters per second. If it
was big enough to retain much of its relative velocity, those two in
the house wouldn't have been around to ask questions afterward.
Nonetheless, strange things do happen, so who knows.

On the other hand, maybe they simply meant "chipped a small divot out
of the floor's surface."
--
Dave
  #4  
Old December 22nd 08, 10:40 PM posted to sci.astro.amateur
Chris L Peterson
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Posts: 10,007
Default Possible meteorite hit?

On Mon, 22 Dec 2008 15:39:22 -0500, Dave Typinski
wrote:

On the other hand, maybe they simply meant "chipped a small divot out
of the floor's surface."


That's how I took it. Rather small meteorites have been known to chip
concrete. You're correct, however, that if the hole was big, it would
probably not have been caused by a meteorite.
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
  #5  
Old December 22nd 08, 11:26 PM posted to sci.astro.amateur
George Normandin[_1_]
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Posts: 1,022
Default Possible meteorite hit?


"Chris L Peterson" wrote
...
On Mon, 22 Dec 2008 15:39:22 -0500, Dave Typinski
wrote:

On the other hand, maybe they simply meant "chipped a small divot out
of the floor's surface."


That's how I took it. Rather small meteorites have been known to chip
concrete. You're correct, however, that if the hole was big, it would
probably not have been caused by a meteorite.
_________________________________________________

Chris L Peterson


Chris, Dave: Thanks! Very informative!!

George N
  #6  
Old December 23rd 08, 02:31 AM posted to sci.astro.amateur
White Space Trash
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Posts: 36
Default Possible meteorite hit?


"Chris L Peterson" wrote in message
...
On Mon, 22 Dec 2008 15:39:22 -0500, Dave Typinski
wrote:

On the other hand, maybe they simply meant "chipped a small divot out
of the floor's surface."


That's how I took it. Rather small meteorites have been known to chip
concrete. You're correct, however, that if the hole was big, it would
probably not have been caused by a meteorite.



Disgruntled neighbour?


  #7  
Old December 23rd 08, 03:14 AM posted to sci.astro.amateur
Chris L Peterson
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Posts: 10,007
Default Possible meteorite hit?

On Tue, 23 Dec 2008 01:31:18 GMT, "White Space Trash"
wrote:

Disgruntled neighbour?


Seriously disgruntled if they broke the concrete floor! There was an
interesting meteorwrong a couple of years ago involving a piece of iron
flung out of some sort of industrial machine a fair distance from the
impact (which was against the side of a house). You just never know.
_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
  #8  
Old December 23rd 08, 07:27 AM posted to sci.astro.amateur
Dave Typinski[_3_]
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Posts: 778
Default Possible meteorite hit?

Chris L Peterson wrote:

On Tue, 23 Dec 2008 01:31:18 GMT, "White Space Trash"
wrote:

Disgruntled neighbour?


Seriously disgruntled if they broke the concrete floor! There was an
interesting meteorwrong a couple of years ago involving a piece of iron
flung out of some sort of industrial machine a fair distance from the
impact (which was against the side of a house). You just never know.


I'm guessing disgruntled neighbor as well. A meteor just happens to
be on a trajectory that brings it through the window, *after* reaching
terminal velocity? I'm assuming a window in a wall, not a skylight.
That scenario is certainly possible, but I think "heavy object tossed
through window by kids" has a greater probability. You could easily
chip a concrete floor by tossing the head of a 10 or 15 lb
sledgehammer through someone's window.

I'm curious: what did that couple find in their garage after a search?
If it were a meteor, they oughtta be able to find pieces of meteorite
in the garage if it were heavy enough to noticeably chip the floor.

I have some blocks of solid tungsten, about 1"x2"x3". They make for
curiously heavy paperweights.

It's fun to toss them at guests to test their reaction to unexpected
density. Nice, easy, underhand throw, "here, check this out."

I dropped one on a concrete floor from about 5 feet; didn't even
burnish the tungsten, but it left a small divot in the concrete.
--
Dave
  #9  
Old December 23rd 08, 10:22 PM posted to sci.astro.amateur
George Normandin[_1_]
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Posts: 1,022
Default Possible meteorite hit?


"Dave Typinski" wrote
Chris L Peterson wrote:

On Tue, 23 Dec 2008 01:31:18 GMT, "White Space Trash"
wrote:

Disgruntled neighbour?


Seriously disgruntled if they broke the concrete floor! .....


I have some blocks of solid tungsten, about 1"x2"x3". They make for
curiously heavy paperweights.

It's fun to toss them at guests to test their reaction to unexpected
density........


Dave, et al:

The results are in! The "owners" brought the "rock/meteorite" to Kopernik
Observatory today and one of the Staff (he has a MS in geology) identified
it as a typical glacial debris rounded stone found along the shores of
central New York's lakes and streams.



BTW, I have some 30mm Rini eyepieces that I toss at people with white
flashlights at star parties!



George N

  #10  
Old December 23rd 08, 11:59 PM posted to sci.astro.amateur
Dave Typinski[_3_]
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Posts: 778
Default Possible meteorite hit?

"George Normandin" wrote:

The results are in! The "owners" brought the "rock/meteorite" to Kopernik
Observatory today and one of the Staff (he has a MS in geology) identified
it as a typical glacial debris rounded stone found along the shores of
central New York's lakes and streams.


Thanks for the follow up!
--
Dave
 




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