Just to cherry-pick one question:
Do we have any hard data on the approximate
rate of impacts on the lunar surface?
Lunar seismic data should show the larger impacts,
but the analysis is controversial. More recent (and
more sophisticated) analysis shows more impacts
than we once thought.
But the simple physical reality is that meteoroids
come from far away toward the Earth-Moon System.
The collisional cross-section is influenced by the
gravity field of the Earth-Moon System as the
meteoroid approaches. Geometrically, the fall
influx of the Moon should be about 1/16th of
the Earth's, but gravitational focusing reduces
that to 1/18th -- the Earth hogs the meteoroids.
So, on a square-mile-basis, the Moon gets 12%
fewer meteorites than the Earth. But those figures
are for the top of the "atmosphere." On the Moon,
the surface IS the top of the atmosphere!
On the Earth, we know (roughly) the fall rate
BENEATH the atmosphere, but not at the top of
the atmosphere. Well, you say, meteorites that
don't survive are converted to dust particles in
ablative trails, so just determine how much dust
gets from space to the Earth's surface. Easy.
Seriously complicating that simple idea is the
large amount of meteoric dust, as opposed to
meteoritic dust. That is, material from meteor
streams, which is mostly dust to begin with, so
adds only a little to the lunar impact hazard.
(There are larger pieces in meteor streams
and monitoring the Moon for impacts during
periodic showers always produces a few visible
flashes from energetic events... but only a few.)
The long-term dust influx preserved in the
Earth's ocean sediments is about 25,000 tons
per year. The total mass of meteorites arriving at
the surface of the Earth is likely between 2000
and 3000 TONS per year. Or maybe 200 to 300
tons, depending on whether you favor 90%
ablative loss or 99% ablative loss.
That figure may astound, but it's clear that less
than 1% of all meteorites that survive to the
surface are recovered
Based on these figures for the Earth, the Moon
would get 1300 tons of dust and particles, 140
tons of which would be particles big enough to
worry about. On a square-mile basis, the likelihood
of a meteorite impact of some size bigger than dust
is probably 8 to 12 times greater than the risk of
being whacked on a square mile of the Earth.
But the fact is that even that risk is tiny. Not just
tiny, but tiny-tiny-tiny-tiny-tiny-tiny-tiny-tiny!
Ten times super-tiny is still, well, TINY. Even if
the risk were 100 times greater , it would still be
tiny.
Try an experiment. Put up a tray the size of a
lunar hut in your yard, covered with a film that
will exclude dust, leaves, twigs, that only a meteorite
could puncture, and wait to collect a meteorite.
When you do, divide the wait-time by 10 (or 100
if you like that better), and you have the risk of
lunar meteorite impact, the mean wait time to
an impact (at a minimum).
And, because we worry about it, every room of every
lunar base, lab, facility, shed, hut, homestead,
outhouse, doghouse, cathouse, and -- oh, yeah --
spacesuit will have a HandiPak of Sticky Patches
within arm's reach.
Just get out your list of humans killed by being
struck by a meteorite and increase their number
by ten. (Where'd I put that list?) And this data would
be for a planet with a billion or billions of humans
(increasing the odds of being hit), so reduce that
10x number by 1000 or so. There won't be billions
of people on the Moon for a while, trust me.
It makes me want to go into the Meteorite Life
Insurance business with a policy good for meteoric
death on any planet. High benefit, low monthly
premiums; just present the murderous meteorite
to verify your claim...
Sterling K. Webb
----------------------------------------------------------------------------
----- Original Message -----
From: "Michael Gilmer" <meteoritem...@gmail.com>
To: "Martin Altmann" <altm...@meteorite-martin.de>
Cc: <meteorite-list@meteoritecentral.com>
Sent: Tuesday, June 28, 2011 7:29 AM
Subject: Re: [meteorite-list] trips to the Moon (Moon bases and
meteoriterecovery)
Hi Martin,
I'm no expert, I only play one on the met-list. ;)
But, meteoroids and micrometeoroids would arrive on a variety entry
angles and velocities. Some at steeper angles and high speeds, others
at shallow or oblique angles and lower speeds. ("lower" being
relative) I agree that the more friable types of meteorite would be
shattered or obliterated on contact with the lunar surface - probably
into unrecognizable bits and destined to become part of the lunar
regolith gumbo. Some robust meteorite types like irons, would
probably survive as well. Imagine a large "crater maker" type of
impactor, the energies involved would be enormous. There could well
be shock and shock heating effects that would char or blacken the
surviving shrapnel.
Since the lunar surface is predominately one narrow palette of
indigenous color, we can rule out easily detecting any meteorites at a
glance that are of that same color range - white, light grey, medium
grey, dark grey, But, higher contrast types should be more visible to
the trained eye - pallasites, stony iron, iron, Martian (!?), some
other achondrites. Or, mount a spectrometer to the exploration rover
and look for reflectance feedback from the landscape that matches
preset meteorite types.
I don't know, it's a fanciful whimsy across a distant and bleak world,
and it makes for good speculation. :)
Best regards,
MikeG
PS - we can see the larger impacts on the Moon here from Earth, by
chancing across a flash of light on the lunar surface. Do we have any
hard data on the approximate rate of impacts on the lunar surface?
Our Apollo astronauts were driving golf balls and tooling around in a
rover, and did any of them witness or sense any nearby or even distant
impacts while they were there? Just curious....
--
---------------------------------------------------------------------------------
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On 6/28/11, Martin Altmann <altm...@meteorite-martin.de> wrote:
Hm Michael,
question - if you haven't any atmosphere, which could slow down the
incoming
meteorids,
how many would survive the impact with cosmic velocities, such rocks
are
typically travelling with in the inner solar system, to such a degree,
that
they would lie there in nice sizes usually called "stones"?
(Hmmm and when I'll drive there around with my car, how could I spot
them,
if they haven't any fusion crust or a different color from
oxidation...)
And if they survived the impact, how long would they survive without
being
crunched, smashed, pulverized by other impacts? A little space
weathering we
have there, but else no weathering and no geological activities for 3
billion years - but a permanent bombardment of small and large high
velocity
impacts - having hammered the complete lunar surface into a field of
debris
and dust.
And if you look at the Apollo rocks or into your lunar meteorites,
most of
them witness an extraordinary violent history. Shocked, mixed, full of
tiny
fragments of different rocks, glasses, resolified dust...ect.
On the other hand, iiif meteorites would survive all that on Moon,
why then the astronauts didn't stumble every step over a meteorite, if
they
had 3 billion years to assemble there and no weathering, making them
decaying?
Would be my questions only (not knowledge).
Martin
-----Ursprüngliche Nachricht-----
Von: meteorite-list-boun...@meteoritecentral.com
[mailto:meteorite-list-boun...@meteoritecentral.com] Im Auftrag von
Michael
Gilmer
Gesendet: Dienstag, 28. Juni 2011 04:08
An: James Beauchamp
Cc: Edwin Thompson; meteorite-list@meteoritecentral.com
Betreff: Re: [meteorite-list] trips to the Moon (Moon bases and
meteorite
recovery)
Sorry for all of my typos - I meant to say :
Well taken, and I agree. Part of their mission was to retrieve lunar
samples, but imagine how many meteorites could be found if a team was
put on to the lunar surface with the primary focus of finding
meteorites and ignoring native lunar materials. :)
I'll stop posting now, I am having typing issues and developing
blabber mouth. LOL
On 6/27/11, Michael Gilmer <meteoritem...@gmail.com> wrote:
Hi James,
Well taken, and I agree. Part of their mission was to retrieve lunar
samples, but how imagine meteorites could be found if a team was put
on to the lunar surface with the primary focus of finding meteorites
and ignoring native lunar materials. :)
Maybe Acme H3 Industries, Inc, will have the spare room in their
underground base to lease out space to a meteorite hunting team, and
the necessary scientific equipment to use for the mission (modified
rovers, infrastructure, etc).
Heck, the mining teams might "unearth" (unlune?) buried meteorites
from under layers of regolith.
Best regards,
MikeG
--
----------------------------------------------------------------------------
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Galactic Stone & Ironworks - Meteorites & Amber (Michael Gilmer)
Website - http://www.galactic-stone.com
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-----
On 6/27/11, James Beauchamp <falco...@sbcglobal.net> wrote:
" The Apollo astronauts were not meteorite hunters, nor did they
have any
specific mission or training involving meteorites."
Mike, I don't think that's quite correct. The Apollo crews were
well
versed
in the expected geology, and were looking for quite a diverse lot of
rocks.
They spent many months training with geologists. Certainly, Dr.
Schmitt
was no exception on Apollo 17. "From Earth to the Moon" episode 10
was
an
excellent, even a bit romanticized focus on the geology focus.
I think the focus was (and should have been) more anti-meteorite.
We had
plenty of those. But we didn't have verified lunar samples - to
include
cores and other different types. We needed more of those to verify
the
origins of our companion, and very little time and resources on-hand
to
get
them.
Just my thoughts on the matter. Obviously, I fully admit I should
stay
in
my engineering corner, but couldn't help poking a little. :)
--- On Mon, 6/27/11, Michael Gilmer <meteoritem...@gmail.com> wrote:
From: Michael Gilmer <meteoritem...@gmail.com>
Subject: Re: [meteorite-list] trips to the Moon (Moon bases and
meteorite
recovery)
To: "Edwin Thompson" <etmeteori...@hotmail.com>
Cc: meteorite-list@meteoritecentral.com
Date: Monday, June 27, 2011, 7:43 PM
Hi Edwin, Sterling, and List,
I love a good science-fiction, science-fact, trip into speculation
land. It reminds me of the old pulp sci-fi novels from the 50's and
60's that I have read, with rocketships and moon bases.
Cosmic rays are not the only threat, there are also micro-meteorites
and meteorites. The Late Heavy Bombardment is long over, but there
is
still a lot of debris peppering the Earth and Moon on a regular
basis.
With no atmosphere, the lunar surface is basically naked to
incoming
impactors. A base facility on the lunar surface would be subject to
high-velocity impacts on a random basis.
Now we can all imagine how the lunar surface is probably littered
with
plentiful meteorites. The Apollo astronauts were not meteorite
hunters, nor did they have any specific mission or training
involving
meteorites. The first meteorite recovery team to be stationed on
the
Moon would be the very first people to hunt the surface - the
opposite
of being "hunted out". The problem is the lethal environment
involved. It would be a death-trap full of meteorites if not
handled
properly. The Apollo astronauts could not stay out for the extended
periods necessary to walk a grid or do a meaningful amount of
searching for suspect rocks. Although we have made some
advancements
since then, the lunar surface is still the most hostile, alien, and
lethal environment that an Earthly meteorite hunter could imagine.
Our modern day meteornauts on the Moon would have to rely on radar,
remote rovers, and man-operated rovers.
To have any permanent presence on the Moon, the surface would need a
warning system for incoming impactors. We can assume an
early-warning
detection system, partially automated, that consists of satellites
and
surface-based radars, telescopes, and other sensors. This warning
system would detect potential impactors that are large enough to
damage facilities or personnel. So, we could have a lunar rover that
could carry a small team of 2 individuals over a long distance with
a
meaningful duration (say, several hours, or even "overnight" in some
cases.). These individuals would be dispatched to retrieve
large/heavy meteorites that smaller unmanned rovers could not pick
up.
They could safely travel the surface (relatively speaking) and they
could be warned to evade/avoid a potentially deadly strike by the
warning system. They would still have to worry about the rare fluke
micro-meteorite or one that slips through the detection system, but
it
would be slightly better odds than a crap-shoot.
The bulk of the searching and retrieval would be accomplished by
robust remote-operately rovers. These would be larger than the
current Mars rovers we know so well (thanks for the always reliable
updates Mr. Baalke!), but small enough to be produced on a low to
modest budget. Essentially it would be a "wander and grab" rover
with
a sophisticated optical system than can scan the lunar surface in
high
resolution and provide a "first person" view to the rover operator
who
is located miles away in an underground facility. It's main
attributes would be quickness (to cover larger amounts of real
estate
in a much shorter time span than today's rovers), keen eyes
(cameras),
and economy of travel (able to stay afield for extended periods of
time).
The rover would also have a robotic arm and a collection bin than
can
be hermetically sealed. The operator would use the rover to locate
and retrieve all meteorites within the operating range of the rover.
Those meteorites which are too large, too heavy, or too numerous for
the rover to recover, would be assigned to a manned rover mission to
recover the specimens.
I don't think there would be a lunar base built just to retrieve
meteorites. However, one can envision a scientific base that is an
all-purpose facility to house a number of teams that are based there
for extended periods of time and are rotated in and out.
Astronomers,
chemists, physicists, geologists....the potential uses for a lunar
surface facility would be many and varied, and meteorites could be
one
of those missions.
Instead of ANSMET, we could have MOONMET - now who is going to apply
for the first expedition?
Best regards,
MikeG
--
----------------------------------------------------------------------------
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Galactic Stone & Ironworks - Meteorites & Amber (Michael Gilmer)
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-----
On 6/27/11, Edwin Thompson <etmeteori...@hotmail.com> wrote:
http://www.space.com/1111-private-moon-trips-forecast.html
Dear fellow listers, for only 100 million dollars you can go to the
moon
and
gather your own Lunar specimens. It could be a very profitable
enterprise.
But the rumor mill has it that China will be going to the Moon
next. If
you
go there be sure to dodge those nasty cosmic rays.
There is a society of brainiacs that has designed a substantial
Moon
base.
Sadly that facility must be built beneath the Lunar surface in a
volcanic
cavern to shield the inhabitants from cosmic ray exposure.
Cheers, E.T.
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