Al M. wrote:
"I don't think it would be possible for an astronaut to throw an
object, rock or otherwise out of the orbit of the Earth."
Hi Al, Pete, Friends and Listees,
Haven't kept with this thread, but I thought I'd add this info for the
throwing arm of the astronaut to create an artificial meteorite from
some favorite heights.
I noticed Dr. Grossman mentioned the need for extraordinary evidence
(i.e., claims by necessity must be treated with skepicism, until at
least someone can show you a piece of it).
Here are some of the "physics": the minimum speeds the clever Astronaut
would have TO THROW any object to gain an independent orbit from Earth:
From the International Space station (One of the lowest satellites):
11,412 mph (7,091 Km/h)
From a GPS satellite (nearly the highest):
3,692 mph (5,941 Km/h)
He has to be clever as he needs to throw it exactly in his direction of
motion to make the satellite's speed additive and also away from the
Moon so that doesn't add significant additional speed required. I just
used the 11.2 km/s value at Earth's surface which fails to take into
consideration the air resistance (this is only partly why expecting
material to survive the shear force going up through Earth's atmosphere
is an Extra-ordinary claim). Not a problem - these are the right
answers for space.
The best baseball players on Earth have been clocked at around 100.9
mph.
The best Jai-alai ball has been levered at about 188 mph.
These speeds are taken over a very short distance from the throwing arm
on Earth, so would be nearly the same in space.
BTW, if an astronaut on the Moon wanted to "throw" something out of
Lunar orbit, he would need to throw at 5,315 mph (8,554 Km/h) which
would leave it barely moseying away from a Lunar orbit, but he would
need it to end up at a minumum of over 3,220 mph (5,188 Km/h) more to
then escape Earth.
Throwing things at these speeds is of course hypothetical given the
capabilities.
Back to the original question Earth meteorite possible? to comment:
These same capabilities need to be taken into consideration with
regards to the mass integrity of any Earth ejecta. Assuming an object
can hit Earth fast enough to impart sufficient velocity at cratering
which will survive the trip back up and more importantly an order of
magnitude more to rip it from Earth's gravitational grasp, is like
assuming you can find a Nolan Ryan to pitch a ball at about 12,000 mph.
It is also a possibility that no physical Nolan Ryan exists.
Earth meteorites don't have a chance due to this reason, unless you
make one modifying assumption: That the original impactor causing them
creates a transient vacuum behind it long and straight enough for
backspauled material to find its way out. THAT is an extraordinary
claim unless we are talking major planet smasher and vapor condensation
in space just to make sure the ejecta aren't too small or just plasma
or molecules! Ojo, this means the cloud MUST condense in outer space
while it is moving away at these speeds. That just adds another degree
of complexity. Not impossible, of course. The jury is still out. I'd
repost a recent answer about 6 months ago I made talking about the
atmospheric dynamics required for Earth meteorites to happen but I'm
not good at maintaning these old met-list links as some others :(
Best wishes,
Doug
-----Original Message-----
From: AL Mitterling <[EMAIL PROTECTED]>
To: Meteorite-list@meteoritecentral.com
Sent: Fri, 30 May 2008 7:51 pm
Subject: Re: [meteorite-list] Just Another Question
Hi Pete,
I don't think it would be possible for an astronaut to throw an object,
rock or otherwise out of the orbit of the Earth. (lets not talk about
the Hassablat that got away) Seems like that would be possible but if
you think about it, both the astronaut and the rock are in orbit around
the Sun. Even a hard throw towards the Sun would only start the rock
moving back and forth in roughly the same orbit the Earth is in. You
might have better luck with trying to reduce it's energy (a retro so to
speak throw) so it would loose energy and fall into a tighter orbit
towards the sun. You have to think about the actual speed the Earth is
traveling around the Sun. Any throw would most likely not be able to
leave the Earth/Moon orbit. Even if an astronaut was well away from the
Earth Moon system in order for the astronaut to not drop directly into
the Sun he would have to have an orbit around the Sun. So even throwing
objects without major gravity near by would even be difficult. It's why
objects in the inner solar system have a harder time coming out
(gaining energy) than objects have loosing energy and going in towards
the inner planets and Sun.
Jeff Grossman wrote: to be called a meteorite, an object had to escape
the dominant gravitational influence of its parent body. In this case,
we would say that a terrestrial (Earth) meteorite would be an object
ejected from earth by natural causes (i.e., by impact), which entered
an orbit around the sun and later was re-accreted (fell as a meteoroid,
became a meteor and then meteorite when it survived passage) by and to
the earth.
Jeff states: Nothing like this has ever been found. Its distinguishing
properties might be a fusion crust, evidence for cosmic-ray exposure in
space, and lithology that is completely exotic for its find location.
Without an exposure history (or being an observed fall) it would be a
very tough sell.
Hope that helps. All my best!
--AL Mitterling
Pete Shugar wrote:
So if an object were to be taken into orbit and given excape velosity
> from earth's gravitational well such that it was not in orbit around
> earth, but in orbit around the sun and at a later time reentered >
earth's gravity well, passed thru the atmosphere and survived to >
impact the earth, it would not be a meteorite simply because it was >
not ejected fron terra firma by natural means? Granted that man made >
debri isn't classed as a meteorite but non man made material >
shouldn't be penalized because an astronaught decided to impart >
excape velosity to a rock,puting it into orbit around the sun.
I say material surviving to impact from any source (excluding man >
made) would and should be called a meteorite.
Pete
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