List, Count,
Ejecta get sorted by mass -- big chunks near the crater,
then medium chunks in the middle distance and so on.
At about 300 miles from impact, there is still a noticeable
dustfall from an impact this size. And the smallest particles
get blown into the atmosphere world-wide as micron-sized
dust.
The statistical average speed for ejecta is always less than
the impact velocity because a lot of energy is used up in
the fireball, vaporizing the impactor, vaporizing a roughly
equal mass of target (Earth!), melting target rocks, and lastly,
fracturing target rocks to be ejected.
The chances of a piece of ejecta getting kicked up to even
sub-orbital velocity is small, but with this many pieces in
play, it MIGHT happen to a very small number of pieces. So,
no "large quantities of ejecta" would behave as you asked.
The only real-world example of high speed ejecta is tektites,
which "seem to be" vaporized target rock that condenses into
liquid and cools to a plastic glass very quickly, probably
above the atmosphere. They can travel up to half an Earth
diameter. But that's the only example we have to go by,
and it's mysterious -- why doesn't every impact produce
tektites?
But for 99.9% of ejecta, it's the same old story everywhere
on every planet. Google up pictures of "ejecta blanket."
http://www.google.com/images?hl=en&q=ejecta%20blanket&um=1&ie=UTF-8&source=og&sa=N&tab=wi&biw=967&bih=640
Big, blocky chunks just outside the rim, tapering off to
dust at the edges. That's the interesting thing about kinetic
events -- they're all the same. Once you get up to a good
size, the particular characteristics don't matter much.
In this size of event, an equal weight of impacting ice, or rock,
or iron, or feathers, or rocky road ice cream -- they would
all leave an almost identical crater. All that counts is the
total kinetic energy.
Objects get blasted off planets. Mars meteorites somehow
got off Mars. Lunar meteorites somehow got off the Moon.
There are even folks who think a chunk of Mercury could
somehow get off Mercury (which chunk is the question).
Moreover, they seem to sometimes do it without being
shocked, possibly by being sucked up the tube of vacuum
formed when the impactor blows through the atmosphere.
No one knows how exactly, but it happens, I suspect, as
a rare event.
Not to be callous, but an eight-mile crater is a "medium"
impact, with local effects, not regional effects, not continental
effects, not world-threatening effects. But like any explosion,
it is nastier the closer you happen to be to it.
It could take out about half of the state of Iowa, for example.
Beyond Iowa's borders, damage would be minimal.
Still, Iowa...
Sterling K. Webb
--------------------------------------------------------------------------------
----- Original Message -----
From: <[email protected]>
To: "Sterling K. Webb" <[email protected]>; "Stuart
McDaniel - Action Shooting Supply" <[email protected]>;
"Thunder Stone" <[email protected]>;
<[email protected]>
Sent: Thursday, July 29, 2010 12:13 AM
Subject: Re: [meteorite-list] Scientist Warns Massive Asteroid
CouldHitEarthin 2182
Sterling,
With the understanding that the impactor is of the size you described in
your last.
Could there be significant property damage and human casualties outside
the 100 mile diameter from the fall of matter propelled to great heights
and trajectories?
Is it plausible that large quantities of ejecta could be propelled into
low earth, rapidly decaying orbits and re-enter to cause significant
secondary impact damage vicariously over the earth?
Do you think some material could escape the earth's gravity to become
meteoroids?
Count Deiro
IMCA 3536
-----Original Message-----
From: "Sterling K. Webb" <[email protected]>
Sent: Jul 28, 2010 11:17 PM
To: Stuart McDaniel - Action Shooting Supply
<[email protected]>, Thunder Stone
<[email protected]>, [email protected]
Subject: Re: [meteorite-list] Scientist Warns Massive Asteroid Could
HitEarthin 2182
List, Stuart,
An eight-mile complex crater with a depth of
about a half-mile. Will take 100% casualties out to
about 35 miles and 70% casualties out to 60 miles.
High-speed ejecta 1 cm and up will reach out to
about 100 miles. Within the inner 75-mile-diameter
circle, expect the destruction of almost everything
and the death of almost everybody.
Even at 60 miles away, the fireball will deliver about
4 megajoules per square meter for about 3.5 minutes,
enough to produce deep third degree burns, and
cause trees and grass to ignite, as well as wood and
part-wood structures. Masonry structures would
collapse from the overpressure; steel structures
would survive best.
An ocean strike would form a smaller crater in the
seafloor but the thermal effects would be about the
same (actually a little worse). The tsunami would
be between 250 and 450 feet high. It would be
world-wide, reach far inland in some areas, and
would likely circle the globe more than once.
Either a land or sea strike would likely result in
comparable damages. Numbers would depend on
the population and structural density of the
area. Middle of the Sahara? Thousands. South
China Coast? Tens of millions.
Highly unlikely that any of the materials you
might gather after the region of the crater stopped
glowing would be part of the impactor, almost all
of which would vaporize. Terrestrial fragments
would dominate the region.
Sterling K. Webb
-------------------------------------------------------------------
----- Original Message -----
From: "Stuart McDaniel - Action Shooting Supply"
<[email protected]>
To: "Thunder Stone" <[email protected]>;
<[email protected]>
Sent: Wednesday, July 28, 2010 9:03 PM
Subject: Re: [meteorite-list] Scientist Warns Massive Asteroid Could
HitEarthin 2182
Not a mathematician are you?? LOL..........it's 172 years. Bet that
will
make a nice strewn field!!!
Stuart McDaniel
Lawndale, NC
Secr.,
Cleve. Co. Astronomical Society
----- Original Message -----
From: "Thunder Stone" <[email protected]>
To: <[email protected]>
Sent: Wednesday, July 28, 2010 6:23 PM
Subject: [meteorite-list] Scientist Warns Massive Asteroid Could Hit
Earthin
2182
Wow - that's only 72 years from now... Don't think I'll be around
Greg S.
http://www.foxnews.com/scitech/2010/07/28/massive-asteroid-hit-earth-warn-scientists/?test=faces
Scientist Warns Massive Asteroid Could Hit Earth in 2182
A large asteroid in space that has a remote chance of slamming into the
Earth would be most likely hit in 2182, if it crashed into our planet
at
all, a new study suggests.
The asteroid, called 1999 RQ36, has about a 1-in-1,000 chance of
actually
hitting the Earth, but half of that risk corresponds to potential
impacts in
the year 2182, said study co-author María Eugenia Sansaturio of the
Universidad de Valladolid in Spain.
Sansaturio and her colleagues used mathematical models to determine the
risk
of asteroid 1999 RQ36 impacting the Earth through the year 2200. They
found
two potential opportunities for the asteroid to hit Earth in 2182.
The research is detailed in the science journal Icarus.
The asteroid was discovered in 1999 and is about 1,837 feet (560
meters)
across. A space rock this size could cause widespread devastation at an
impact site in the remote chance that it hit Earth, according to a
recent
report by the National Academy of Sciences.
Scientists have tracked asteroid 1999 RQ36's orbit through 290 optical
observations and 13 radar surveys, but there is still some uncertainty
because of the gentle push it receives from the so-called Yarkovsky
effect,
researchers said.
The Yarkovsky effect, named after the Russian engineer I.O. Yarkovsky
who
proposed it around 1900, describes how an asteroid gains momentum from
thermal radiation that it emits from its night side. Over hundreds of
years,
the effect's influence on an asteroid's orbit could be substantial.
Sansaturio and her colleagues found that through 2060, the chances of
Earth
impacts from 1999 RQ36 are remote, but the odds increase by a magnitude
of
four by 2080 as the asteroid's orbit brings it closer to the Earth.
The odds of impact then dip as the asteroid would move away, and rise
in
2162 and 2182, when it swings back near Earth, the researchers found.
It's a
tricky orbital dance that makes it difficult to pin down the odds of
impact,
they said.
"The consequence of this complex dynamic is not just the likelihood of
a
comparatively large impact, but also that a realistic deflection
procedure
(path deviation) could only be made before the impact in 2080, and more
easily, before 2060," Sansaturio said in a statement.
After 2080, she added, it would be more difficult to deflect the
asteroid.
"If this object had been discovered after 2080, the deflection would
require
a technology that is not currently available," Sansaturio said.
"Therefore,
this example suggests that impact monitoring, which up to date does not
cover more than 80 or 100 years, may need to encompass more than one
century."
By expanding the timeframe for potential impacts, researchers would
potentially identify the most threatening space rocks with enough time
to
mount deflection campaigns that are both technologically and
financially
feasible, Sansaturio said.
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