[meteorite-list] Lunar Leonid Strikes

From: Gerald Flaherty <grf2_at_meteoritecentral.com>
Date: Fri, 01 Dec 2006 15:01:00 -0500
Message-ID: <00e801c71583$70f17580$6402a8c0_at_Dell>

STILL WONDERING?!?

In the early 1990's, taking the advice of a populist TV astromomer, I lined
an overturned plastic rubbush LID with white plastic, filled it with clean
water, and left it, balanced on some cinder blocks, on the lawn overnight at
the height of the Perseids.
Being relatively unsophisticated about meteorites at the time, I rushed
outdoors, small magnet in hand, with the enthusiasm of a "child on Christmas
morning" to greet the dawn after witnessing a rather brilliant meteor
display on the marshes adjecent to the house the previous night.
Low and behold, I was rewarded by the thrill of discovery!!
Quite obvious against the white plastic, under an inch or two of water black
specks jumped up into the arms of the magnetic field. One in particular,
measuring over a millimeter needed no hand lens to appreciate, although I
spent endless minutes studing thier coarse, textured surfaces, enthralled
that I had become so rich.
Soon after I was a victim of the NONAME [or should I say "Perfect"]
Halloween storm of Oct 1991.
Some of my most prize possessions, these tiny spects, were lost as was much
my material "wealth".
I think of them often, even now as I stare at my modest Lunar and Martian,
Chondrite, Pallasite and Irons.
For nearly three years I've been lucky enough to have discovered, joined and
learned much from this List. It's funny how this thread has brought back
that twinge of loss once experienced decades ago.
Jerry Flaherty
----- Original Message -----
From: "Rob McCafferty" <rob_mccafferty at yahoo.com>
To: <Impactika at aol.com>; <meteorite-list at meteoritecentral.com>
Sent: Thursday, November 16, 2006 5:50 PM
Subject: Re: [meteorite-list] LEONID'S MORE HOPE FOR COLLECTORS


> This is going to be one of my more thoughtful and
> intellectual contributions with a serious question
>
> --- Impactika at aol.com wrote:
>
>> Sorry to disappoint you but meteor shower do not
>> produce meteorites.
>> They are minute fragments and burn completely in the
>> atmosphere.
>>
>> Too bad the Media does not know that.
>>
>
>
> Hmm. While most people with a background including
> astrophysics know this - of which I like to include
> myself as one - I have often wondered about the old
> meteorite/meteor shower conundrum
>
> I am pretty sure there are no meteorites which
> correspond date-wise to meteor showers but is this
> actually the case?
>
> While the average comet detritus is dust, it is not
> impossible, surely, for a much larger chunk to get
> ejected from a comet? The current theories of
> explosive outgassing would surely allow a chunk that
> broke off to achieve escape velocity. Is it beyond the
> realms of possibility that one of these may sit in the
> orbit of a comet waiting its transition into the
> atmosphere?
> I will confess, I have not the mathematical skill
> (primarily) nor time (secondarily) to work out the
> orbital dynamics of a big-enough chunk that broke off.
> I suspect that a large chunk is more likely to follow
> the orbital path of the main body than the dust which
> can get disperesed by radiation pressure quite
> quickly, though theres the radiative effect during
> rotation which effects orbits too (I forget its name).
> Will that cause it to move out of the comet's orbital
> path?
>
> We know comets fragment. We have photographic evidence
> of it. We know the fragments spread out (ditto). Why
> can we not have meteorites from comets?
>
> Just because we haven't yet, doesn't mean it is
> impossible. Mass extinctions have not been observed
> dur to major impact events yet, either. We all know
> that doesn't mean it can't happen or hasn't happened
> in the past. I am not sure my scenario is any
> different.
>
> That probe which crashed into the comet recently
> (again, I forget the name..I have a full time job to
> hold down), did it determine the consistency of the
> surface?
>
> Are comets and their fragments too fragile to survive
> the transition to Earth from space? If they are, then
> isn't it time we stopped likening Murchison to a
> comet?
>
> NOT SCIENTIFIC BIT.
>
> Or is it that "we just don't know?" That phrase which
> is likely to cause me to create "the dead Scientists
> Society". A secret forum where top scientists can, in
> confidence, air their misgivings and failures in
> understanding which society will not let them admit.
>
> Funny, isn't it? As society dumbs down, it expects
> the egg-heads to know and solve more! Lazy bast**ds!
>
> Rob McC
>
>
>
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Jerry Flaherty
----- Original Message -----
From: "Ron Baalke" <baalke at zagami.jpl.nasa.gov>
To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>
Sent: Friday, December 01, 2006 2:10 PM
Subject: [meteorite-list] Lunar Leonid Strikes


>
> http://science.nasa.gov/headlines/y2006/01dec_lunarleonid.htm
>
> Lunar Leonid Strikes
> NASA Science News
> December 1, 2006
>
> Dec. 1, 2006: Meteoroids are smashing into the Moon a lot more often
> than anyone expected.
>
> That's the tentative conclusion of Bill Cooke, head of NASA's Meteoroid
> Environment Office, after his team observed two Leonids hitting the Moon
> on Nov. 17, 2006. "We've now seen 11 and possibly 12 lunar impacts since
> we started monitoring the Moon one year ago," says Cooke. "That's about
> four times more hits than our computer models predicted."
>
> If correct, this conclusion could influence planning for future moon
> missions. But first, the Leonids:
>
> Last month, Earth passed through a "minefield" of debris from Comet
> 55P/Tempel-Tuttle. This happens every year in mid-November and results
> in the annual Leonid meteor shower. From Nov. 17th to Nov. 19th both
> Earth and the Moon were peppered with meteoroids.
>
> Meteoroids that hit Earth disintegrate harmlessly (and beautifully) in
> the atmosphere. But the Moon has no atmosphere to protect it, so
> meteoroids don't stop in the sky. They hit the ground. The vast majority
> of these meteoroids are dust-sized, and their impacts are hardly felt.
> But bigger debris can gouge a crater in the lunar surface and explode in
> a flash of heat and light. Some flashes can be seen from Earth.
>
> During the passage through Tempel-Tuttle's debris field, Cooke's team
> trained their telescopes (two 14-inch reflectors located at the Marshall
> Space Flight Center) on the dark surface of the Moon. On Nov. 17th,
> after less than four hours of watching, they video-recorded two impacts:
> a 9th magnitude flash in Oceanus Procellarum (the Ocean of Storms) and a
> brighter 8th magnitude flash in the lunar highlands near crater Gauss.
>
> "The flashes we saw were caused by Leonid meteoroids 2 to 3 inches (5 to
> 8 cm) in diameter," says Cooke. "They hit with energies between 0.3 and
> 0.6 Giga-Joules." In plain language, that's 150 to 300 pounds of TNT.
>
> How do you get so much energy out of a 3-inch meteoroid? "Leonids travel
> fast - about 144,000 mph," he explains. "At that speed, even a 3-inch rock
> packs tremendous energy."
>
> For comparison, the ESA's SMART-1 probe crashed into the Moon on Sept.
> 2nd, delivering 0.6 Giga-Joules of energy to the lunar surface - the same
> as the brighter of the two Leonids.
>
> "Leonid impacts are as energetic as the crash of a 700-lb spacecraft!"
> says Cooke.
>
> With these latest detections, Cooke's group has tallied a dozen "lunar
> meteors" since Nov. 2005. Most were sporadic meteoroids--meaning they
> are part of no annual shower like the Leonids, but just random chips of
> asteroids and comets floating around in space. Cooke estimates that for
> every four hours they observe the Moon, they see one bright flash caused
> by the impact of a large meteoroid.
>
> And that's surprising. "Our best models of the lunar meteoroid
> environment predict a much lower rate - only 25% of what we are actually
> seeing." The problem may be with the computer models: "They're based on
> observations of meteors in the skies of Earth," and those data may not
> translate well to the Moon.
>
> The solution? "We need to spend more time watching the Moon," says
> Cooke. "With more data, we can draw stronger conclusions about the
> impact rate."
>
> NASA needs that kind of information to decide, e.g., if it's safe for
> astronauts to go moonwalking during a meteor shower; to calculate the
> necessary thickness of shielding for lunar spacecraft; and to answer the
> question, how often will a moonbase be punctured by a Leonid?
>
> Next up: The Geminid meteor shower on December 13th-14th. Once again
> Earth and Moon will be peppered with meteoroidsi - this time from the
> asteroid 3200 Phaethon. Says Cooke, "we'll be watching."
>
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Received on Fri 01 Dec 2006 03:01:00 PM PST