[meteorite-list] PROPOSAL: THE CARANCAS CRATER PERU documentation: camera stereo-pair aerial photography FRM: Dirk Ross...Tokyo

From: drtanuki <drtanuki_at_meteoritecentral.com>
Date: Sun, 7 Oct 2007 02:06:54 -0700 (PDT)
Message-ID: <955447.50519.qm_at_web53203.mail.re2.yahoo.com>

Dear DRs., Sterling, and List Members,

 I apologize in advance for mailing several of you
DRs. a message in a public forum, but this is the most
feasible means to expediently accomplish this request
(some of you may be unaware of the context of this
post; we are trying to document the recent impact
crater in Carancas, Peru prior to its "natural"
destruction and request your kind assistance; thank
you).
  For the Honorable Doctors from Peru I apologize that
this is written in English and not in Spanish; I
cannot write in Spanish.

  Helium balloon(s) might be the easiest and most
practical, unless someone has access to an airplane or
jet aircraft.

  B/W, B/W or Color IR (don`t forget to add an IR
filter to the camera if an amateur attempts), Color,
or all of them for filming of stereo-pairs?

  Anyone have friends with private, commercial or
military aircraft access in the area? Any chance that
a military, NASA, European satellite will be crossing
the area and multi-spectral imagery can be obtained?

  I have worked with tripod poles and camera for such,
but the size of the area eliminates this possibility.

  If anyone has connections with potential persons or
groups to accomplish this task it will certainly help
in documenting the crater before further damage by
humans, rain and wind.

  Hopefully, this can done by a professional. An
ammeter is more than likely to fail.

 Thank you all in advance for helping in accomplishing
this task.

 Comments appreciated and most welcome. Please comment
on this list or privately.

Sincerely, Dirk Ross...Tokyo

PS Thank you Sterling for your valuable comments.

------------------------------------------------------
> List,
> > The Carancas crater needs to be photographed
> from
> > the air with a high resolution camera and a
> > stereo-pair should also be made.
> > Secondly, if the crater is to survive any rain
> > thought should be given as to how it could be
> > preserved, with low tech and cost in mind.
> > Are their any plastics or cement compounds that
> > could be sprayed over the crater that would work?
> Or
> > should a plastic cast of it be made to at least
> have
> > a
> > full-sized replica? If Peru wants a National
> > Landmark
> > and tourism to the site they need to take some
> kind
> > of
> > urgent action so that they have more to show than
> a
> > mud hole full of trash.
> > Any thoughts or ideas?

------------------------------------------------------


"Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
wrote:
Hi, List

Dirk's suggestion of close aerial stereo pairs is the
best suggestion in a while. It would not only permit
measurements of the crater but it would map the
ejecta blanket, the symmetry (or asymmetry) of
which is an important datum.

The impact excavated about 350+ cu. meters of soil and

rock, weighing about 500-600 tons, of which about
25 cu. meters or 40 tons is to be found in the rim.
The ejecta blanket extends up to 200 meters from
the crater and covers roughly 125,000 sq. meters. If
the impact had a low angle, the ejecta blanket would
be asymmetric, but we don't know because nobody...
etc., etc.

I noticed that the pictures of the crater Graham
posted
(and which were taken soon after the event, I presume)
a number of good-sized rocks showing whitish patches
lying on the near ejecta blanket. In Mike's pictures
of
the crater from the same angle, taken days later, the
ejecta blanket looks the same, but all those
"white-patch"
rocks are gone. So, there were some multi-kilo stones,

6 to 8 at the least, that were collected.

The north portion of the rim is higher than the south
portion; the impactor came from the north. The slope
of the crater wall on the south is less than on the
north;
this argues a steep angle of impact for the object
(>60
degrees), which means that it came more or less from
the "top" of the sky.

The time of the impact was shortly before noon, the
time when the other object in the "top" of the sky was
the Sun. Now, an object can graze the top of the
Earth's
atmosphere at a wide range of initial angles and end
in
a downward path steeper than its encounter path.
That's
pretty much the way it works. But a very steep
downward
path can only result from a fairly steep angle of
approach.

This would suggest that the object was approaching the
Earth from the sunward side at altitude of 60 degrees
or more.
Very likely, its initial encounter velocity was high,
given the
characteristics of such an orbit, if it was eccentric
enough
to be a Main Belt object (which most orbit-determined
meteorites turn out to be).

In that case, the question of fragmentation or
episodes of
multiple and progressive fragmentation is not as
relevant as
it might be. The lateral dispersion velocity of the
fragments
is very slow compared to the high speed of the object
(now
the cluster) and fragments have very little time to
disperse.

We have all seen fireball videos in which
fragmentation
takes place. Even in prolonged flight, the separate
fragments
are seen to be moving in virtually the same path at
slightly
different velocities (because of their differential
drag values).
In a high speed, very high angle impact, whether it's
one
huge chunk or 1000 individual pieces hardly matters to
the
result if they are closely, even intimately,
clustered. The
crater could have been made by a very tight cluster,
but
only a very tight cluster.

The size and persistence of the smoke trail suggests
that
ablation was proceeding at a rapid rate, with great
loss of
mass; this probably produced a high rate of
deceleration.
To be seen easily, noticeably, head-turningly at noon
means
it must have been very bright indeed.

We have many reports of the fireball from Desaquadero,

20 km.* NNE, on the shore of Lake Titicaca. It would
be
a big help if someone could determine if there were
any
sightings from locations further NNE, like Tiquina.
The
absence of sightings 50 or 100 km. away would indicate

a steep descent; finding more distant reports would
indicate
a shallower descent. It would help rough in the
geometry
of the fall.
[* The INGEMMET report says 20 km. from Carancas to
Desaguadero. The map says 10.8 km. The distance of
Carancas from the crater has been given as 1200 meters

up to 5000 meters.]

But I now have a reason to believe it is more likely
to
have been a single (surviving) object than a
fragmenter.

Rob noticed Doug and I playing one-on-one volleyball.
Our respective uniforms, his "Slow Impact" jersey and
my "Fast Impact" jersey, were provided by local
merchants
trying to keep us off the street. It's a good thing it
was a
one-on-one game, because everybody's on the "Slow
Impact" Team because we get More Meteorite that way.

The point is well taken that the best way to get a
meteoroid
to make that difficult personal transition to a
meteorite is to
slow down, sneak up on the Earth's atmosphere
sidewise,
and to be as frisbee-shaped as possible. I've made
that point
on the List many times before: low entry speed, low
angle of
approach, and an aerodynamic shape.

But here we have a different problem. I see every sign
that
this was a fast impact, to the annoyance (I'm sure) of
those
who want More Meteorite or a big Jilin clone in the
mudpit.
So, how do we get a fast object to the ground without
it
burning up in the process?

We change its shape. We are taught (I was) to
generalize
to an abstraction. Ask a physicist to model anything
and
the first thing he will do is "consider the object as
a sphere
of radius N." (Look at Chris Peterson's email to Mike
on
10/02/07; there's a man too wise to waste time playing

volleyball with imaginary balls and an invisible net.)
What
if the object ISN'T a sphere?

I've seen lots of pictures of very small asteroids and
none of them
were spheres: bent peanuts, dumbbells, pancakes with
dome-poles,
and something vaguely the size and shape of a
stripmall-in-space,
but not one sphere. The smaller the object, the more
irregular.

What if the meteoroid was roughly a cylinder 4-5 times
longer
than wide? How would it fare hitting the atmosphere at
60
degrees tangent to the ground and 17,000 meters a
second?
Well, it depends on its weight, almost entirely, as it
turns out.
One ton just barely gets to ground at a few hundred
miles per
hour and ten tons bores in at 8600 meters per second,
intermediate
weights at all intermediate speeds, any speed you
want. None of
them ablate away completely and none of them fragment.
They
all make a crater.

What a remarkable result!

Back in February '07, when we were talking about a new
and
big Holbrook find, I posted this reference which has
an
analysis of that strewnfield, asserting that it was
the product
of a multiple fragmentation. It uses composite scaling
analysis
to model strewnfields, and in so doing the authors
discover that
the original SHAPE of the meteoroid has a much
stronger influence
on the descent to Earth than we realized, may in fact
be the big
determining factor in what gets to ground and how fast
or
slow it does it.

The link was publicly accessible then, but is now only

accessible to those with big bulgy pockets or members
of The Institutional Academic Scholars Union Local. We

must keep our arcane knowledge out of the hands of
poor
people; it is our duty as a civilization, eh, what?
(Sorry;
I get this way when I Google too much...)
http://www.iop.org/EJ/article/0295-5075/43/5/598/node4.html
L. Oddershede, A. Meibom, J. Bohr: Scaling analysis of
meteorite
shower mass distributions. EUROPHYSICS LETTERS, 1998,
Vol.43, No.5, pp.598-604

Turns out the only way you can get the original mass
of
the Sikhote-Alin object to the ground is to make it,
too, a
long shape, ratio 3:1 or more. A chip off some bigger
block.

The link that Mike just posted to the List:
http://home.comcast.net/~C_Shipbaugh/Impact.html
are calculations by a nanotechnologist who has
obviously
never analyzed a meteorite fall before and manages to
get it amazingly right (physics is physics, you know).
He
does silly things like over-estimating the volume of
the crater
by a factor of two because he does not know it's
conical!
Doha!

He arrives at a 5 ton TNT impact without apparently
knowing
that the seismic signal was rated at 5 tons of TNT.
He, too,
thinks it was a slow impact, which is why he favors 10
or
20 ton objects, but says 4.5 tons at 3000 m/sec is
most likely
guess (which is the same as 1.125 ton at 6000 m/sec).

He introduces the factor of shape in the form of the
"ballistic
parameter or coefficient," but then goes ahead and
models it
as a SPHERE. See, all physicists think alike (well,
most).

You are probably saying about now, what is this all
about?
Well, remember the glory days of starting into space
and how,
after envisioning spaceships all our Buck Rogers life,
we were
amazed to see the first spaceship, the Mercury
capsule, was
an Ice Cream Cone?

It re-entered on its butt, er, blunt, end for maximum
resistance.
The re-entry end was a segment of a sphere (probably
so the
physicists could model it better). And everyday dumb
people
said, "Why don't they come back with the pointy end
down;
wouldn't that be faster? Better yet, why isn't it all
sleek and
thin like a jet plane?"

Well, we know the answer to that one, of course.
Because a long
cylindrical object with an (ablated) point would bore
into the ground
at tremendous speed. That's the ballistic parameter.
We wanted the
Mercury capsule to SLOW DOWN. If we wanted it to make
a big
crater, it would have looked like the Bell X-1 without
wings.

All it takes to get any meteoroid to the ground at a
high speed
is to stop imagining that God made all the billions of
little rocks
in space perfect spheres to make life easy for
physicists. He likes us...
But not that much.


Sterling K. Webb


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Received on Sun 07 Oct 2007 05:06:54 AM PDT