[meteorite-list] Report increases and debris streams

From: E.P. Grondine <epgrondine_at_meteoritecentral.com>
Date: Thu, 19 Feb 2009 09:31:07 -0800 (PST)
Message-ID: <584252.36434.qm_at_web36904.mail.mud.yahoo.com>

Hi Sterling -

It would seem to me that the carbonaceous chondrite (comet debris) streams may be easiest to pick out, but then their survival as meteorites may make that difficult.

As far as the asteroid streams go, the whole thing reminds me of a bad science fiction movie: asteroids in gravitationally stable orbits for a long time, then either run into each other or are dislodged by a comet and sent Earthward.

It's the clumps in both that the prediction of falls needs to sort out.

While we've had many studies of orbits from films of entry paths, I have seen little mention of intercept speeds derived from these films, or from reports for that matter.

E.P. Grondine
Man and Impact in the Americas

PS - I gave my little introduction to meteorites talk to a friend's three young children last night. It was a real pleasure, so my thanks to all here who made it possible. Funny thing, at the end of it they were wondering how they could get hold of meteorites of their own.

> Hi, EP, List,
>
> I meant Asteroid Belt and/or Asteroid Zone (having
> seen both terms). Streams of small debris tend to
> distribute
> themselves along the entire orbital path, or clump in
> multiple
> locations along the orbit in short order after formation. I
> referred to that by saying that not only does the Earth
> have
> to go through the intersection but something in that orbit
> has to pass through the intersection at the same time (not
> always the case, as you point out).
>
> Comets can be prograde or retrograde, and big fragments
> from old collisions can go in any direction and/or
> orientation.
> But collisions with another prograde object are just as
> dangerous as any other Whack, depending on its orbital
> eccentricity, major axis, and so forth. It only has to
> intersect
> the Earth's orbit at one point, and the relative
> velocities at
> that point can be low or they can be high or anywhere
> in-between, depending on orbital characteristics.
>
> Even the extreme in gentle collisions, when an object
> and the Earth approach each other with a resulting relative
> velocity of near-zero, is no fun, because gravity will see
> to
> it that the object that is almost motionless with respect
> to
> the Earth will arrive at the surface of the Earth at 11,186
> meters per second! The range of chances (like all chances)
> is essentially random.
>
>
> Sterling K. Webb
> -----------------------------------------------------------------------------
> ----- Original Message -----
> From: "E.P. Grondine"
> <epgrondine at yahoo.com>
> To: <meteorite-list at meteoritecentral.com>;
> "Sterling K. Webb"
> <sterling_k_webb at sbcglobal.net>
> Sent: Wednesday, February 18, 2009 3:31 AM
> Subject: Re: [meteorite-list] Report increases and debris
> streams
>
>
> Hi Sterling -
>
> When you say "Belt" and "Zone", which
> ones are you referring to?
>
> While since my stroke orbital mechanics is not my strong
> suite,
> It seems to me that you're thinking of an asteroidal
> debris stream
> as being like a cometary debris stream, which is to say
> rather uniform along
> its path. I don't think that would be the case. Second,
> wouldn't the orbit
> of a asteroidal debris stream would be different than a
> cometary debris
> stream; always co-directional with Earth's orbit around
> the Sun?
>
> E.P.
>
> --- On Mon, 2/16/09, Sterling K. Webb
> <sterling_k_webb at sbcglobal.net> wrote:
>
> > From: Sterling K. Webb
> <sterling_k_webb at sbcglobal.net>
> > Subject: Re: [meteorite-list] Report increases and
> debris streams
> > To: epgrondine at yahoo.com,
> meteorite-list at meteoritecentral.com
> > Date: Monday, February 16, 2009, 6:00 PM
> > Hi, EP, List,
> >
> > > I don't know if the intersections of the
> Earth
> > > with either cometary or asteroidal debris streams
> > > would necessarily be annual.
> >
> > For an object to intersect the Earth, it has to
> intersect
> > the Earth's orbit at a given point. Points along
> the
> > Earth's
> > orbit are dates of the year in the human calendar, so,
> > yes, these intersections would be annual (or twice
> annual
> > if the object orbit was similar in size to the
> Earth's
> > orbit
> > but tilted with respect to it, a rare chance).
> >
> > Not only does the Earth have to be at that point in
> its
> > own orbit (a date) but there has to be an object in
> the
> > "stream" orbit that goes through that
> > intersection at
> > the very same time as the Earth. (This is why there is
> > little need to post traffic cops there...)
> >
> > The orbits of small bodies, however, change rather
> > rapidly under the gravitational influence of the
> larger
> > bodies. Such a "stream" would like precess,
> which
> > would move the intersection along the Earth's
> orbit,
> > from one date of intersection to the next or previous
> > day, in a time-scale of a few centuries or less. The
> > intersection date might change a day every decade
> > or more... or less.
> >
> > This rapid change is why we've never been able to
> > pin down a suspected "stream-crossing" from
> old
> > historical observations. Every meteorite whose orbit
> > was determined turned out to be from the Belt or the
> > Zone... out there, anyway. I found very interesting
> the
> > recent posting that Buzzard Coulee may not turn out
> > to be from out there but from an inner system orbit.
> > That orbit would be worth checking for evidence
> > of a "stream"!
> >
> >
> > Sterling K. Webb
> >
> --------------------------------------------------------------------
> > ----- Original Message -----
> > From: "E.P. Grondine"
> > <epgrondine at yahoo.com>
> > To: <meteorite-list at meteoritecentral.com>
> > Sent: Monday, February 16, 2009 4:54 PM
> > Subject: [meteorite-list] Report increases and debris
> > streams
> >
> >
> > Hi Elton, all -
> >
> > Elton - "Back to a general note: we are seeing
> weekly
> > and monthly spaced
> > major fireballs including large meteorite falls."
> >
> > Perhaps this is just the effect of the internet, along
> with
> > the realization
> > that the falls can lead to cash.
> >
> > "Statistics tell me that we are only sampling a
> > portion of a much larger
> > asteroidal debris field in crossing earth orbit."
> >
> > I don't know if the intersections of the Earth
> with
> > either cometary or
> > asteroidal debris streams would necessarily be annual.
> What
> > you probably
> > would need to do would be to sort known falls by type,
> > subtract days between
> > falls, and then look for multiples. That's about
> as
> > far as I can take this
> > kind of analysis now, and I know it's less than
> what
> > would be needed.
> >
> > Imagine the result if you will: "Ah, March 12.
> Well
> > tonight perhaps a nice
> > pallasite is going to fall at 3 in the morning. Time
> to
> > start up the old
> > fireball survey system. Wonder what it will have for
> us
> > tomorrow morning?"
> >
> > E.P. Grondine
> > Man and Impact in the Americas
> >
> >
> >
> > ______________________________________________
> > http://www.meteoritecentral.com
> > Meteorite-list mailing list
> > Meteorite-list at meteoritecentral.com
> >
> http://six.pairlist.net/mailman/listinfo/meteorite-list


      
Received on Thu 19 Feb 2009 12:31:07 PM PST