[meteorite-list] Re: Earth Originating Meteorites

From: David Freeman <dfreeman_at_meteoritecentral.com>
Date: Thu Apr 22 09:42:06 2004
Message-ID: <3A71A4E1.80585F3E_at_fascination.com>

Hi Kelly, Bob, Vern, and Ernie;
I spent eight years working in a very large open pit coal mine and half of
that time was spent drilling and blasting rock. The cretaceous overburden
and inter burden had varying densities and toughness, and the powder factors
used to fracture the rock types did vary considerably. The cap rock layer
just above the coal was the finer silts tone of the formation and was the
hardest to fracture for digging...which is the main point of the whole
exercise.
My connection to the thread is how many tons of fly rock I witnessed first
hand. Fly rock is wasted energy as no fracturing of the formation takes
place if the energy is expelled upward with a handful of free flying rocks
instead of coupling to the formation and fracturing rock, and thus allowing
for ease of excavation. It made great entertainment though, and great
experience for ejecta theories of mine.
A rock that is sitting on the surface and lifted with energy will rise and
not really fracture much on its way up to say a couple thousand feet
elevation, boom and up she goes, even try stemming a blast hole with rocks
will simulate a cannon going off. Rock that is still attached firmly to
terra firma will fracture and have much internal structural damage.
What really fractures rock is when it stops real fast.....imagine a 50 pound
rock of hardness 6 mohs that is dropped down a few thousand feet through
thin air (6,500 feet) and hits a hard packed road bed and stops in about 5
milliseconds. That is what really breaks the rock. Rock will survive the
blast up, but will loose cohesion upon impact. In directly, did the rock
get pre stressed when it was "ejected"?
Another one for simulation, place a 30 pound rock hardness 6 mohs on top of
a partial roll of 50 grain blasting cord and touch it off. With the loose
coupling of the rock just sitting on the cardboard roll, the rock goes up(
and a large air blast is produced), and the rock is a little worn for the
ride up, the stop at the bottom seems more detrimental to the rock. A
similar rock placed directly on a single line of blasting cord where the
rock is directly touching the cord when detonated will result in the rock
having a inch deep cut in the rock if it was not lifted skyward to fly (
rock was heavier than the ability of the cords energy to over come the
gravity and establish lift), and just picked up a little.
It was evident to me that the coupling factor...cushioning of initial
acceleration seemed to be a very determining factor in the survival of the
ejecta...and if it fell on the haul road, on a truck, or in a field when it
returned to earth. Blasting cord detonation is 30,000 feet per second (?),
and the ammonium nitrate velocity of detonation is 25,000 feet per second (
or approximately, my memory fails me in some numbers).
In fracturing the rock, one needed to blast to a free face in order to allow
the energy to work the rock to a place where it could become free to expand
and fracture. A few times when starting a new pit, we made some blind
blasts to start a free face. Fly rock was three to five times greater in
height and angles of exit when there was no readily available path to free
movement. We would be about a mile back from blind face shots. I ran out
the lead in line, played on the pit radio, and inniated the blasts...with
adult supervision of course.
I have a few pictures around if anyone would like to see fly rock for a
little visual candy of energy releasing against gravity.
I hope this was food for thought. If you are still here, the interesting
thing is that the shock wave going out doesn't break the rock as much
effectively as the returning shock wave reversing back in toward the zone of
detonation.
Have a blast, more fun than matches!
Dave Freeman


Kelly Webb wrote:

> Hi, Bob, Vern, List,
>
> I love it when a thread wanders into one of my fondest obsessional
> areas!
>
> The best reference on the transfer of impact materials from one planet
> to another is:
> Science, March 8, 1996 v271 n5254 p1387(6).
> Title: The exchange of impact ejecta between terrestrial planets.
> Author: Brett J. Gladman, Joseph A. Burns, Martin Duncan, Pascal Lee
> and Harold F. Levison
>
> Someone (possibly Bernd Pauli) posted the text of this article to
> the List a year or so ago. Gladman is using large scale step-by-step
> integration simulation for this, which requires a huge amount of very
> heavy computer time lifting. His findings are not based on abstract
> dynamic arguments (which have a lousy track record for prediction). He
> has done a lot more work on the question, which was summarized in the
> September, 1999, issue of Sky & Telescope.
> Fully 50% of the simulated Earth (or Moon) ejecta returns to the
> Earth (or Moon) on a time scale of 10,000 years up to 10,000,000 years.
> The 10,000 year time scale applies to objects that wander around in the
> vicinity of the Earth-Moon system; the longer time scales for objects
> that achieve independent heliocentric orbits but get swept up again.
> Frankly, if you admit that the Earth does or has ever been hit with
> impactors big enough to produce ejecta, then I can't really see how you
> could rule out "Earthites!" The real question is a) how to identify
> them, and b) how to prove it.
>
> Just as interesting (to me at least) is that Gladman's runs show
> that there should three times as many chunks of Venus reaching the earth
> as chunks of Mars. So, if there are 15 Mars meteorites, where in the
> hell are the 45 Venusian meteorites? Jay Melosh calculated that over the
> history of the solar system there should have been about 500,000,000
> chunks of Mars arriving on Earth. I cross-wire these two conclusions and
> ask, how could we have misplaced 1,500,000,000 chunks of Venus? And, oh,
> yeah, what about the 50,000,000 chunks of Mercury? If we have 15 chunks
> of Mars, we should have 1.5 chunks of Mercury to go with the 45 chunks
> of Venus.
> Since the current conventional wisdom on Venus regards the planet as
> essentially terrestial but with a variant history, there would be little
> to distinquish a chunk of Venus from a chunk of Earth. The Russians'
> published table of bulk crustal composition for Venus are virtually
> identical to what would be found on much of the terrestial crust.
> Personally, I think contemporary planetary science has a bad case of
> looking at the Worlds with Earth-colored glasses, but, hey, that's just
> my opinion. So, if you find a rock that appears terrestial but has a
> fusion crust, check its argon isotope ratios (40/38/36) along with
> everything else.
>
> The truth is that theory is not truth; facts are truth. Here are
> these humble little pieces of Mars. We can hold them in our hands. They
> made it. They got here. They didn't get melted. They didn't get
> vaporized. (Well, okay, they got whacked good.) An Earth or Venus rock
> accelerated to escape velocity only needs 10 to 15 seconds to traverse
> the atmospheric blowout path to atmosphere-free heights. Another problem
> we have is trying to visualize some poor little rock getting booted to
> excape velocity with one swift kick. An Earth rock accelerated to escape
> velcity in one second only needs about a 1,120 gee kick. There are a lot
> of terrestial rocks that could withstand 1000 gee's without even
> fracturing. Given a 2-3 second acceleration, they would need to hold up
> to only 300-500 gee's. The critical factor is not that first derivative
> (how velocity changes with time) but the second derivative (how
> acceleration changes with time); as long as the force is not applied
> "instantaneously" but builds up, even over a few tenths of a second, the
> rock will survive. Anyone got a mass driver and a bucket of rocks? It
> would be fun to find out!
>
> Bob V wrote:
> "I need references to counter those that say that there are
> calculations which show that the energy required to launch an Earth rock
> into space is more than enough to completely melt or vaporize it."
> Yeah, it takes about 1.25 x 10^10 ergs per gram to melt rock and the
> kinetic energy of escape is about 1.2 x 10^12 ergs per gram, so
> obviously it is impossible for ANY object to escape the earth, whether
> it be rock or rocket. (In fact, this argument was used in the early 20th
> century to "prove" that space travel was impossible!) Yeah, if you fired
> the Space Shuttle out of Jules Verne's Space Cannon built by the
> Baltimore Gun Club in 1867, it would melt. So what? The "those who say"
> are operating under the assumption that the transfer of kinetic energy
> to the object must be instantaneous and equally obviously, it not only
> is it not instantaneous, there is probably no way to make it really
> instantaneous, which is a mathematical fiction. It's strictly a straw
> man argument: let's propose an impossible case and then prove it's
> impossible. GIGO.
>
> Maybe the escapee rocks lie a way back from the crater. The
> landscape as a whole at the impact starts to move, shoved aside until it
> reaches hypersonic velocity carrying chunks of buckling terrain with it.
> The impactor vaporizes and the landscape REALLY starts to move, then the
> full shock wave arrives in a another second and boots a rock already
> going mach 10 up to mach 30 or so. Yes, a lot of rock gets crushed,
> melted, and even vaporized, but the lucky rock just ahead of the wave
> get flicked away like a drop of spray into space to surf the void. Bye,
> bye.
>
> Anyway, I don't worry too much about how it happens exactly, because
> what we do know is that it does happen. Details would be nice and I
> would relish them, but I can wait.
> So, how does one convince the world? Only one way I know of. Find
> the rock and prove it. Rub their noses into it until they notice. We've
> been through this over and over again; how do you prove to the French
> Academy that rocks fall from the sky?
>
> Here's a brief table of Gladman's simulations with how much ejecta ends
> up where:
>
> Ejecta From Mercury
> Mercury 80%
> Venus 7%
> Earth/Moon 0.5%
> Mars 0%
>
> Ejecta From Venus
> Mercury 0.5%
> Venus 50%
> Earth/Moon 9%
> Mars 1%
>
> Ejecta From Earth/Moon
> Mercury 0%
> Venus 15%
> Earth/Moon 50%
> Mars 0.1%
>
> Ejecta From Mars
> Mercury 0%
> Venus 4%
> Earth/Moon 5%
> Mars 3%
>
> You'll notice the totals don't equal 100%. The remainder suffers a
> variety of fates, but a lot of it leaves the solar system at about 30
> km/sec, to arrive at alpha Centauri in 50,000 years, Sirius in 90,000
> years, epsilon Erdani in 112,000 years, and so forth, carrying certain
> small living specks with them in some cases, only to be blasted off
> those newly life-infected worlds by more impacts, and so on, which would
> transfer earth based life to the entire Milky Way Galaxy in only a
> billion years or so. Hello, cousins...
>
> Kelly Webb
>
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Received on Fri 26 Jan 2001 11:25:06 AM PST