Ancient Meteor Blast May Have Caused Extinctions (Forwarded)

On Jun 16, 10:34 pm, "George" wrote:
"mathematician" wrote in message

ups.com...



On Jun 15, 9:01 pm, "George" wrote:
"mathematician" wrote in message

groups.com...

On Jun 15, 2:12 pm, "George" wrote:
"George" wrote in message

...

"Bob Cain" wrote in message
m...
George wrote:

I am very familiar with impact calculators. I use the one on the
University of Arizona'a web site all the time. But you are
missing
the
point here. If it strikes a 10,000 feet thick ice sheet in a
remote
area,
there necessarily isn't going to be any forest that the resulting
impact
can burn because the entire landscape is covered by ***a 10,000
feet
thick
ice sheet***.

*Until* the object impacts. Do you think that ice would stop that
size object from impacting whatever is beneath it with enough
energy
left to splash magma all over the damn planet and start fires on
the
other damn side of it? Maybe it would only result in steam, as
you
imply, but that's not what I saw on TV. :-)

Bob

Umm, Bob (I can call you bob, right?). You should take what you
see
on
TV with a grain of salt.

Using the University of Arizona's impact calculator and inputing
data
for
a 5 km diameter bolide with a density of dense rock impacting (in
this
case, water, since ice isn't available as a target in the impact
calculator) 10,000 meters of water, for an observer 1,000 km away,
here's
what we get:

Your Inputs:
Distance from Impact: 1000.00 km = 621.00 miles
Projectile Diameter: 5000.00 m = 16400.00 ft = 3.10 miles
Projectile Density: 3000 kg/m3
Impact Velocity: 11.00 km/s = 6.83 miles/s
Impact Angle: 45 degrees
Target Density: 1000 kg/m3
Target Type: Liquid Water of depth 3048.00 meters, over typical
rock.
Energy:
Energy before atmospheric entry: 1.19 x 1022 Joules = 2.84 x 106
MegaTons TNT
The average interval between impacts of this size somewhere on
Earth
during the last 4 billion years is 1.0 x 107years
Major Global Changes:
The Earth is not strongly disturbed by the impact and loses
negligible
mass.
The impact does not make a noticeable change in the Earth's
rotation
period or the tilt of its axis.
The impact does not shift the Earth's orbit noticeably.
Crater Dimensions:
What does this mean?

The crater opened in the water has a diameter of 48.9 km = 30.3
miles

For the crater formed in the seafloor:
Transient Crater Diameter: 25.3 km = 15.7 miles
Transient Crater Depth: 8.94 km = 5.55 miles

Final Crater Diameter: 38.7 km = 24 miles
Final Crater Depth: 0.889 km = 0.552 miles
The crater formed is a complex crater.
At this impact velocity ( 12 km/s), little shock melting of the
target
occurs.
Thermal Radiation:
What does this mean?

At this impact velocity ( 15 km/s), little vaporization
occurs;
no
fireball is created, therefore, there is no thermal radiation
damage.
Seismic Effects:
What does this mean?

The major seismic shaking will arrive at approximately 200
seconds.
Richter Scale Magnitude: 8.7
Mercalli Scale Intensity at a distance of 1000 km:

III. Felt quite noticeably by persons indoors, especially on
upper
floors of buildings. Many people do not recognize it as an
earthquake.
Standing motor cars may rock slightly. Vibrations similar to the
passing
of a truck.

IV. Felt indoors by many, outdoors by few during the day. At
night,
some awakened. Dishes, windows, doors disturbed; walls make
cracking
sound. Sensation like heavy truck striking building. Standing motor
cars
rocked noticeably.

Ejecta:
What does this mean?

The ejecta will arrive approximately 494 seconds after the
impact.
At your position the ejecta arrives in scattered fragments
Average Ejecta Thickness: 3.65 mm = 0.144 inches
Mean Fragment Diameter: 570 micrometers = 22.4 1/1000 of an inch

Air Blast:
What does this mean?

The air blast will arrive at approximately 3030 seconds.
Peak Overpressu 14900 Pa = 0.149 bars = 2.12 psi
Max wind velocity: 33.2 m/s = 74.2 mph
Sound Intensity: 83 dB (Loud as heavy traffic)
Damage Description:

Glass windows will shatter.

So the impact doesn't spew hot lava all over the place since
there
is
no fireball (thus, no thermal radiation damage), and certainly if
it
struck ice instead of water, the effects would likely be much less
than
this for this distance.

Here is the link, try it:

http://www.lpl.arizona.edu/impacteffects/

George

Yes OK, I took a quick look to the reference text (link to this paper
was found from your reference).

I have also found one present possible dangerous asteroid. Here are
references of it which I found:

Present situation in the Risk Page (many of these will be removed
when enough accurate measurements are available)

NeoDys Risk Page

http://newton.dm.unipi.it/cgi-bin/ne...iskpage:0;main

One present example (diameter=0.270 km, H=19.7, this is maybe
dangerous)

(99942) Apophis - impactor table
Object: 99942

date MJD sigma sigimp dist +/- width
stretch p_RE exp. en. PS
YYYY/MM (RE) (RE) RE/
sig MT
------------------------------------------------------------------------------------------------
2036/04/13.371 64796.371 -2.470 0.000 1.15 +/- 0.003 3.32E+03
2.07E-05 8.26E-03 -2.57
2042/04/13.720 66987.720 -2.494 0.000 1.41 +/- 0.000 1.12E+06
5.26E-08 2.10E-05 -5.24
2044/04/13.296 67718.296 -2.434 0.000 2.08 +/- 0.000 6.27E+05
3.57E-08 1.42E-05 -5.44
2069/04/13.078 76849.078 2.112 0.000 0.97 +/- 0.000 3.74E+05
4.41E-07 1.76E-04 -4.56
2069/10/15.971 77034.971 1.466 0.000 0.48 +/- 0.160 1.52E+06
3.81E-07 1.52E-04 -4.63
2072/10/15.333 78130.333 -3.870 0.000 0.48 +/- 0.089 6.09E+06
1.57E-10 6.26E-08 -8.03
2076/07/30.873 79514.873 2.720 1.214 34.89 +/- 26.902 1.49E+07
3.73E-11 1.44E-08 -8.69

Based on 1000 optical observations (of which 5 are rejected as
outliers)
from 2004/03/15.108 to 2006/08/16.627, and also on seven radar data
points
on 2005/01/27, 2005/01/29, 2005/01/31, 2005/08/07 and 2006/05/06.

Coordinates are given on the Target Plane
Unit is one Earth radius, but impact cross section
has radius between 2.15 and 2.16 Earth radii

http://newton.dm.unipi.it/cgi-bin/ne...s:Apophis;main
http://newton.dm.unipi.it/cgi-bin/ne...:Apophis;statp....
http://newton.dm.unipi.it/cgi-bin/ne...:Apophis;prope....
http://earn.dlr.de/nea/099942.htm
http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=99942;orb=1 (simulation of the
orbit,
possible impact velocity can be esitimated from this ?)

Conversion of Absolute Magnitude (H) to Diameter

http://cfa-www.harvard.edu/iau/lists/Sizes.html

This is quite inaccurate method to estimate diameters, but it is only
available method ?

Hannu

As of August 5, 2006, the threat level for Apophis had been reduced to
level 0. As for your question about estimating diameters, I don't have
a
good answer for you at this time. I'll check back with you if I figure
one
out.

George

I roughly estimated the velocity difference of Apophis and Earth (they
are orbiting same direction quite close each others as we see in the
simulation pictures referenced above) and I got that possible
impact velosity would be about 1 km/s, if I calculated right ?

The exact diamenter is little uncertain and there was an earlier
estimation of H which was H=19.20, which gave range
430 m-970 m (http://earn.dlr.de/nea/99942.htm, printed 19.8.2005),
but present estimation is 270 m ?

How big tsunamis would this cause if it would hit in some ocean ?

Hannu

According to the impact calculator, if the object is 270 meters in
diameter, and consists of dense rock, and is traveling at 1 km/s at a 45
degree angle relative to the earth's surface, it will break up in the
atmosphere at an altitude of 28,200 ft. If the object is 439 meters in
diameter, then using the same parameters as before, the object will break
up in the atmosphere at an altitude of 28,400 ft, which is an odd result.
Using a diameter of 970 meters, the object would break up at 28,500 ft,
again, an odd result. Obviously, either the program has some errors in the
...

read more »

A. It would then be like "a shot with a shotgun" (v = about 1km/s, hit
angle to the Earth's
atmosphere = more close to 90 than 45 ?), many fragments of different
sizes results ?

How do we know that there is no big iron fragments included in the
structure of Apophis ?

If I remember right there was also some fragmented iron (?) meteorite
which hit to
Estonia about 2400 years ago (there was a TV-program some time ago
about
this in finnish TV) ?

I just think that could these meteorites about 13000 years ago, about
2400 years ago
and Apophis have anything properties in common ?

B. I found an abstract from the net about determination of H (and also
diameter) of Apophis:

( http://journals.cambridge.org/action...ine&aid=998112
)

---COPY BELOW-----
Proceedings of the International Astronomical Union (2007), 2: 451-454
Cambridge University Press
doi:10.1017/S1743921307003560
Published online by Cambridge University Press 03May2007

Contributed Papers
Albedo and size of (99942) Apophis from polarimetric observations†
Alberto Cellinoa1, Marco Delbòa1a2 and Edward F. Tedescoa3

a1 INAF-Osservatorio Astronomico di Torino, strada Osservatorio 20,
10025 Pino Torinese, Italy email:
a2 Observatoire de la Côte d'Azur, BP 229, Nice, France email:

a3 University of New Hampshire, USA email:

Abstract.

We have obtained the first accurate determination of the albedo of
(99942) Apophis, by means of polarimetric observations carried out at
the VLT. The observations allowed us to obtain the slope of the
polarization-phase curve of this object, from which an albedo estimate
of 0.33 ± 0.04 could be obtained. From our observations we also
obtained a new estimate of the absolute magnitude: H = 19.7 ± 0.2
(assuming G=0.25, which applies to S- and Q-type asteroids). Based on
these results, we derive for the size of Apophis a value of 270 ± 30
meters. The accuracy of this size estimate is mostly related to
uncertainties in H, whereas the obtained albedo value should be
considered more robust. Our observations convincingly show that
polarimetry is an effective and efficient tool to obtain accurate
albedos and sizes for small and faint potentially hazardous asteroids.

Key Words: Asteroids; polarization

Footnotes
† Based on observations obtained at the European Southern Observatory
(ESO), DDT request 276.C-5030
---COPY ABOVE-----

http://journals.cambridge.org/action...ine&aid=998112

Hannu

In sci.bio.paleontology mathematician wrote:


Sheesh ... care to post edit next time? You don't have to post ALL the
previous text with each post.


--
Thomas T. Veldhouse

Software is like sex; it's better when it's free.
-- Linus Torvalds

To George:

A. It would then be like "a shot with a shotgun" (v = about 1km/s, hit
angle to the Earth's atmosphere = between 0 to 90 (45 is average
estimate ?)),
many fragments of different sizes results ?

How do we know that there is no big iron fragments included in the
structure of Apophis which could possible cause tsunamis if hit into
ocean?

If I remember right there was also some fragmented iron (?) meteorite
which hit to Estonia about 2400 years ago (there was a TV-program
some time ago about this in finnish TV) ?

I just think that could these meteorites about 13000 years ago, about
2400 years ago and Apophis have anything properties in common
(and maybe there exist also other possible years ) ???

I found one interesting reference (possible could be related to this
phenomena if enough properties in common exists ???) but
unfortunately I don't have that paper on my hands now:

Kerr, R. A., 1992.
Earth Gains a Retinue of Mini Asteroids.
Science, vol. 258, no. 5081, Oct 16, p. 403.

I must read this in the library. I comment it later if I find it.

B. I found an abstract from the net about determination of H (and also
diameter) of Apophis:

http://journals.cambridge.org/action...omPage=online&...

--COPY BELOW-----
Proceedings of the International Astronomical Union (2007), 2: 451-454
Cambridge University Press
doi:10.1017/S1743921307003560
Published online by Cambridge University Press 03May2007

Contributed Papers
Albedo and size of (99942) Apophis from polarimetric observationsâ€*
Alberto Cellinoa1, Marco Delbòa1a2 and Edward F. Tedescoa3

a1 INAF-Osservatorio Astronomico di Torino, strada Osservatorio 20,
10025 Pino Torinese, Italy email:
a2 Observatoire de la Côte d'Azur, BP 229, Nice, France email:

a3 University of New Hampshire, USA email:

Abstract.

We have obtained the first accurate determination of the albedo of
(99942) Apophis, by means of polarimetric observations carried out at
the VLT. The observations allowed us to obtain the slope of the
polarization-phase curve of this object, from which an albedo estimate
of 0.33 ± 0.04 could be obtained. From our observations we also
obtained a new estimate of the absolute magnitude: H = 19.7 ± 0.2
(assuming G=0.25, which applies to S- and Q-type asteroids). Based on
these results, we derive for the size of Apophis a value of 270 ± 30
meters. The accuracy of this size estimate is mostly related to
uncertainties in H, whereas the obtained albedo value should be
considered more robust. Our observations convincingly show that
polarimetry is an effective and efficient tool to obtain accurate
albedos and sizes for small and faint potentially hazardous asteroids.

Key Words: Asteroids; polarization

Footnotes
â€* Based on observations obtained at the European Southern Observatory
(ESO), DDT request 276.C-5030
---COPY ABOVE-----

http://journals.cambridge.org/action...omPage=online&...

Hannu

(I'am sorry about I did not notice long reply texts
which google generated automatically. They are quite
annoying.)

I found one discussion in the the of this article
(Kerr, R. A., 1992.
Earth Gains a Retinue of Mini Asteroids.
Science, vol. 258, no. 5081, Oct 16, p. 403. )

----Partly COPIED BELOW------

From: (Jim Scotti x2717)
Newsgroups: sci.astro,sci.space
Subject: "Earth Gains a Retinue of Mini-Asteroids"
Message-ID: u
Date: 31 Oct 92 07:55:47 GMT
References:
Sender:
Distribution: na
Organization: Lunar & Planetary Laboratory, Tucson AZ.
Lines: 66

In article
(Paul Dietz) writes:
Science (10/16/92, page 403), reports that Gehrels and colleagues in
the Spacewatch program have detected 8 very near earth asteroids over
the last two years with sizes from 5 to 100 meters. This implies that
at any time, there are as many as 50 mini-asteroids passing between
the Earth and Moon every day. This figure is some 100 times larger
than had been inferred from observations of the number of larger
bodies.

Since the Tunguska event is thought to have been due to a 40 meter
body, and such events were calculated to occur once every 2 to 3
centuries, something is screwy here.

Not really screwy. The number of 50 meter objects is enhanced by
about 10 times and the Tunguska type events probably happen once
or a few times per century. Remember, 3 out of 4 enter over water
and may be less likely to be detected. Also, perhaps a large
fraction of them disintegrate higher in the atmoshpere, causing
a much smaller disturbance in the lower atmosphere than that of
the Tunguska event. Also, the best guess I've heard for the size
of the Tunguska progenitor is between 50 and 100 meters. The 10
meter sized objects are enhanced by a factor of 100 and the trend
from the larger objects to the smallest is a gradual transition
that starts at around 100 meters size.

The orbits of the bodies are unexpectedly similar to Earth's.
Two have orbits more like earth's than any known body; one was that
asteroid that was mistaken for a spent rocket body.

Also known as 1991 VG.

These couldn't be Frank's minicomets, could they? His putative
objects are supposedly in prograde, earth-like orbits, to reduce the
impact velocity enough to avoid observational constraints.

Frank's minicomets were estimated to be 10-30 meters in size. The
number of objects in this size that he estimated to account for
what was probably detector noise was at least a million times the
the number extrapolated from the larger Near Earth asteroid population
and therefore is a population at least 10,000 times more numerous
than
what has now been found by Spacewatch. In short, with our
sensitivity,
we should see at least 1000 of Frank's minicomets each NIGHT!!!!!! I
think the Spacewatch survey has now effectively disproven Frank's
hypothesis used to explain his so called "atmospheric holes".

Incidentally, an earlier CCD developed by Spacewatch in the
early 1980's (an old RCA 320x512 chip) was used by a colleague
of Frank's from JPL to survey for the minicomets directly. This
investigator claimed to have detected at least one such object
on two consecutive images. Without consulting the Spacewtach
crew, he announced his "discovery". When we were finally able
to look at his images, we concluded that what he was looking
at was detector noise!


Paul F. Dietz


Jim.
---------------------------------------------
Jim Scotti
}
Lunar & Planetary Laboratory
University of Arizona
Tucson, AZ 85721 USA


From: (Jim Scotti x2717)
Newsgroups: sci.space
Subject: "Earth Gains a Retinue of Mini-Asteroids"
Message-ID:
Date: 4 Nov 92 20:47:44 GMT
References:
Sender:
Distribution: sci
Organization: Lunar & Planetary Laboratory, Tucson AZ.
Lines: 62

In article
writes:
{Actually, I ) wrote this:}
Not really screwy. The number of 50 meter objects is enhanced by
about 10 times and the Tunguska type events probably happen once
or a few times per century. Remember, 3 out of 4 enter over water
and may be less likely to be detected. Also, perhaps a large



I wonder... Could this be the explanation for the non-radioactive
mushroom cloud seen by airline pilots in the Pacific one day in the
late 70's - early 80's? It was never connected to any source that I
am aware of.

I vaguely remember hearing something about this. The rate of small
asteroid impact could very well account for such an event. I doubt
we can conclusively identify it as an asteroid impact, but the
probability of such an event happening is quite high.

Some theorized it was caused by an undersea volcanic explosion, but
no one succeeded in associating it with one. It was not a nuclear
explosion, although some at first suggested that. It is unlikely to
have been a non-nuclear explosion, ie no ships disappeared and I'm
not sure I see a motive for an experimental blast in that part of the
world.

In the absence of further evidence, we'll just have to add small
asteroid impacts as a possibility.

Just a thought, although I would not expect a mushroom cloud from
such a comet strike. I'm not sure I can even see a mechanism for
creating one from a Tunguska class strike.

The mechanism is quite understandable. You have an object moving
at hypersonic velocity as it enters the atmosphere. A stony or
stony iron object could easily survive into the low atmosphere where
the aerodynamical stress catastrophically ruptures it and it explodes
just like a bomb. The estimated impact energies of 10-100 meter
objects traveling at typical velocities is measured in the kilotons
on the small end to 10s of megatons on the large end and that kinetic
energy has to go somewhere! Smaller objects fracture high in the
atmosphere and appear as bright bolides which leave trails and
fragments along the way. If the object is strong enough, it might
survive largely intact with most of its kinetic energy and might
create an impact crater such as was made about 50,000 years ago when
the Diablo Canyon Meteor crater was formed in Arizona. That crater
is thought to have been formed by the impact of a stony iron object
only about 30 meters in diameter. Objects strong enough to survive
atmospheric entry are fortunately rare.

By the way, the Tuguska event was observed by residents of the
region and their description of the explosion matchs that of a nuclear
bomb blast quite closely.

Jim.
---------------------------------------------
Jim Scotti
}
Lunar & Planetary Laboratory
University of Arizona
Tucson, AZ 85721 USA
---------------------------------------------

From: (Jim Scotti x2717)
Newsgroups: sci.astro,sci.space
Subject: "Earth Gains a Retinue of Mini-Asteroids"
Message-ID:
Date: 7 Nov 92 01:16:56 GMT
References:
u

Sender:
Distribution: na
Organization: Lunar & Planetary Laboratory, Tucson AZ.
Lines: 44

In article (Dan Tilque)
writes:
(Jim Scotti x2717) writes:
(Paul Dietz) writes:

Since the Tunguska event is thought to have been due to a 40 meter
body, and such events were calculated to occur once every 2 to 3
centuries, something is screwy here.

Not really screwy. The number of 50 meter objects is enhanced by
about 10 times and the Tunguska type events probably happen once
or a few times per century.

This sparked a memory, but unfortunately not a detailed one.

There was a second (but less powerful) Siberian meteor-explosion
sometime after Tunguska. I seem to remember that it was in either the
20's or the 40's, but the name of it totally eludes me.

Anyone know about this?

Yup, I do. You are remembering the meteorite fall called "Sikhote-
Alin"
which happened in 1947 in Siberia. The fall created about 200 small
craters of the non-explosive type created by the fall of large
objects
traveling relatively slowly, perhaps at terminal velocity. The
largest
crater was about 26.5 meters in diameter. I think that about 50 tons
of
material was recovered and the progenitor was estimated as being
about
200 tons before atmospheric entry. I suppose the object would have
been
around 5 meters diameter before entry and was probably a stoney iron.

This size object probably hits the Earth around 10 times per year and
I suppose about 1% of them are stoney iron, so a fall of this type
probably happens on the order of once a decade.

---
Dan Tilque --

Jim.
---------------------------------------------
Jim Scotti
}
Lunar & Planetary Laboratory
University of Arizona
Tucson, AZ 85721 USA
---------------------------------------------

----COPY ABOVE--------------------

Hannu