[meteorite-list] grains of sand

From: Robert Verish <bolidechaser_at_meteoritecentral.com>
Date: Thu, 7 Nov 2013 17:23:08 -0800 (PST)
Message-ID: <1383873788.36543.YahooMailNeo_at_web142502.mail.bf1.yahoo.com>

Hi Paul,

If what you're saying is true, then there are many many more meteors that we are not seeing (but would be visible to instruments more sensitive than are eyes, or to astronauts in Earth orbit that are closer to the "action").?

I think that a grain of sand is large enough to ionize enough oxygen and nitrogen atoms to make the light phenomenon visible from the ground.? (In the few, lucky times that I observed an actual meteor through the eyepiece of a telescope, I noticed that they had a peculisr appearance.? I was struck by the two bands of diffuse light [probably ionized gas], one on each side of an extremely thin, bright line [the ablating meteor - IAU definiton].? These bands of light may have been a reflection off of thin clouds or high-altitude ice crystals, but in any case, it only adds to our ability to see a "grain of sand" meteor.

I have the opposite opinion, as well, about a related matter.? I feel that we over-estimate the percentage of material that is ablated away during the fireball/meteor phase.? (Probably is too off-subject.)


I also feel that the too-often-used phrase "nothing made it to the ground - it all burned-up" is too ill-informed.? How is it physically possible for a cobble-pebble-sandgrain to continue traveling fast enough to completely ablate down to total nothingness?? It's my opinion that (depending on altitude) for all sizes of incoming debris (even at cosmic-velocity) there is a certain retardation-point where, once it is reached, ablation can no longer occur.? I would not be surprised if this minimum size is in the fine-pebble grain-size range, which is certainly still "findable".? One way that this conjecture could be substantiated, is if there were actually a gap in the population of small meteorites between pebble and micro-spherule.? Has this already been recorded in Antarctica?


Out the door and on my way to Imperial County,
Bob V.


On Thursday, November 7, 2013 6:12 AM, Paul Gessler <cetuspa at shaw.ca> wrote:

Was wondering about the statement that shooting stars we see are no bigger
>than grains of sand???
>I here it used all the time and haven't? really given it any thought. I
>don't buy it!
>I don't think a grain of sand would be able to generate enough light to be
>visible from earth?
>Has anyone actually measured these grains of sand? If so how was it done.
>Where did this (factoid)
>originate and is there any validity to it?
>I could see gravel sized debris producing what we see but not sand and
>smaller.
>
>Any one care to comment?
>
>Paul Gessler
>
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Received on Thu 07 Nov 2013 08:23:08 PM PST