[meteorite-list] Small Asteroid 2010 AL30 Will Fly Past TheEarth

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Wed, 13 Jan 2010 21:46:05 -0600
Message-ID: <AA51199FF2714B888390A861DB13653C_at_ATARIENGINE2>

Hi, Larry, Chris, List,

I was thinking, for "heavy object in a meteoroid stream,"
the 1975 impact on the Moon that was detected by seismograph
experiment left behind by one of the Apollo missions (15?). It
was at the June 30 peak of the diffuse beta Taurids and has
been interpreted as one of them.

The seismograph record covered 1972-1978, and the 1975
impact corresponded that of a 2.5-ton object, the biggest
impact recorded by those seismographs on the Moon.

Oh God, I'm going to have to document this, aren't I?

Of course, it could have been a sporadic with the signature of
a beta Taurid, but I think that's stretching coincidence. The
five day bracket June 28-July 2, 1975, recorded more one-ton
objects slamming into the Moon than the entire remainder of
the total seven-year record.

A-ha! There it is:
http://articles.adsabs.harvard.edu//full/1978LPSC....9.3615D/0003615.000.html

So, yes, I'd have to say there are heavy objects embedded in
"meteoroid streams." Does something as heavy as two 1975
Volkswagens count as "heavy"? Would you be convinced if it
had been as heavy as a Lincoln Town Car? It was! (Wikipedia
says 1970's Town Cars weighted "4500 to 5300 lb (2000 to
2400 kg)")

I stand my ground. If it's as heavy as a Lincoln Town Car...
it's heavy.


Sterling K. Webb
--------------------------------------------------------------------------------------
 ----- Original Message -----
From: <lebofsky at lpl.arizona.edu>
To: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
Cc: <lebofsky at lpl.arizona.edu>; "Chris Peterson"
<clp at alumni.caltech.edu>; "Meteorite-list"
<meteorite-list at meteoritecentral.com>
Sent: Wednesday, January 13, 2010 5:09 PM
Subject: Re: [meteorite-list] Small Asteroid 2010 AL30 Will Fly Past
TheEarth


> Hi Sterling:
>
> Yes, it is not uncommon for definitions to be, unfortunately for the
> general public, to be in the context of who is studying what.
> Cratering
> people do not necessarily care what caused the impact (asteroid or
> comet)
> other than in the modeling that includes parameters such as density,
> etc.
>
> In the case of Meteor Crater, the only reason that we have meteorites
> (according to the work of Melosh and others) was probably due to the
> original body breaking up prior to impact. If I remember correctly,
> about
> 50% broke off the orginal body, giving us the meteorites, and 50%
> stayed
> in one piece and made a big hole (being totally vaporized in the
> process).
>
> One flaw in your example in a meteor stream is that there is nothing
> that
> big. You may get very bright fireballs (bolides), but nothing starts
> out
> big enough to make it to the ground. It is all small stuff (as far as
> we
> know).
>
> LArry
>
>> Hi, Larry, Chris, List,
>>
>> In many ways, this mess is about the "terms
>> of the trade." It is essential that those working
>> in a specific specialty understand what each
>> other mean when they discuss the subject.
>>
>> The use of "the terms impactors and bolides
>> for the things that make holes in the ground,"
>> as Larry called it, makes discussion quick and
>> effective for those with a "planetary science"
>> perspective.
>>
>> Chris' "meteoroid => meteor => meteorite," pretty
>> much the same as my first definition, is -- yes --
>> non-IAU-compliant, but from the viewpoint of the
>> study of meteoritic fall, it is clear and effective
>> terminology, well understood.
>>
>> Those who study "meteor showers" use the term
>> meteoroid as a generic for all the objects contained
>> within a given "meteoroid stream," even if the object
>> weighs many tons and is really big enough to be
>> technically an "asteroid." If it's in a "meteoroid
>> stream," it must be a meteoroid, right?
>>
>> In the real world the working vocabulary is, in
>> practice, determined by those that do common
>> work, for their own use. But it can't be a "private
>> language'" That's where the IAU (should) come in.
>> Opinions may vary on how well they do that job.
>>
>> The Big Iron that made Meteor Crater is too big to
>> qualify for "meteoroid." It has to be called an asteroid.
>> Even the original body of Sikhote-Alin was too big
>> to be a meteoroid. So we have asteroids that make
>> meteorites. Even 2008 TC3 was meteoroid by size
>> but asteroid by designation. The entire classification
>> system of meteorites has as one major purpose
>> identifying the parent body in the "Asteroid Zone."
>> Tracking the origin of "meteoroids" that result in
>> meteorites has, so far, always traced them back to
>> Main Belt asteroids.
>>
>> And while we often don't know the original mass of
>> most objects that result in found meteorites, most of
>> the smallish bodies we call meteoroids are too small to
>> result in meteorites...
>>
>> It could therefore be more common to get meteorites
>> from asteroids, and meteoroids may not produce very
>> many meteorites.
>>
>> Something about that terminology bothers me.
>>
>>
>> Sterling K. Webb
>> ----------------------------------------------------------------------------
>> ----- Original Message -----
>> From: <lebofsky at lpl.arizona.edu>
>> To: "Sterling K. Webb" <sterling_k_webb at sbcglobal.net>
>> Cc: "Meteorite-list" <meteorite-list at meteoritecentral.com>
>> Sent: Wednesday, January 13, 2010 6:02 AM
>> Subject: Re: [meteorite-list] Small Asteroid 2010 AL30 Will Fly Past
>> TheEarth
>>
>>
>> Hi all again:
>>
>> Those who study impacts on Earth and other bodies tend to use the
>> terms
>> impactors and bolides for the things that make holes in the ground
>> but
>> too
>> big leave any meteorite. This gets around the asteroid/comet problem.
>>
>> I just got this from WIkipedia (same article that Sterling used?:
>>
>> "Bolide:
>>
>> The word bolide comes from the Greek ?????, (bolis) which can mean a
>> missile or to flash. The IAU has no official definition of bolide and
>> generally considers the term synonymous with fireball. The bolide
>> term
>> is
>> generally used for fireballs reaching magnitude -14 or brighter.[8]
>> The
>> term is more often used among geologists than astronomers where it
>> means
>> a
>> very large impactor. For example, the USGS uses the term to mean a
>> generic
>> large crater-forming projectile "to imply that we do not know the
>> precise
>> nature of the impacting body ... whether it is a rocky or metallic
>> asteroid, or an icy comet,... Astronomers tend to use the term to
>> mean
>> an
>> exceptionally bright fireball, particularly one that explodes
>> (sometimes
>> called a detonating fireball)."
>>
>> I do not remember in all the emails I read this morning someone
>> asking
>> about the dark phase. Since the definition of a meteoroid is an
>> object
>> in
>> an independent orbit aroung the Sun, once it is in the dark phase, it
>> is
>> no longer in an independent orbit and is probably going to survive
>> and
>> so
>> might as well be called a meteorite. I have always said that the
>> rocky
>> bit
>> that causes a meteor is a meteoroid (which we cannot see).
>>
>> I tell kids that if you can see the thing that is causing the
>> meteor/fireball---duck!
>>
>> Now, since I have not had my morning coffee (mentioned this to
>> Sterling),
>> the problem with the IAU definition is that it states that a
>> "meteoriod
>> is
>> significantly smaller than an asteroid." If that is true, what is
>> between
>> a large meteoroid and a small asteroid? A dwarf asteroid (sorry, need
>> my
>> coffee)!
>>
>> Now, in support of the IAU and my concern with the proposed Royal
>> Astronomical Society definition is that we are observing things
>> smaller
>> than 10 meters and those are given asteroid designations, they are
>> asteroids. There is no IAU meteroid nomenclature committee!
>>
>> I think that you need the line between large meteoroid and small
>> asteroid
>> to be left "fuzzy." Define a meteoriod as up to 10 meters, but if it
>> is
>> close enough to the Earth and it gets detected and given a
>> designaton/name
>> then it becomes (reclassified as) an asteroid. This makes sense from
>> the
>> perspective that, when we learn more about something, its designation
>> can
>> change (such as large Trans Neptunian Objects becoming dwarf planets
>> as
>> our knowledge of them increases).
>>
>> Enough said before my first shot of caffeine.
>>
>> Larry
>>
>>
>>
>>> Just to make things even more confusing,
>>> the IAU itself has approved the use of the
>>> term "meteor" in a dual sense to include the
>>> physical body itself, thus equating "meteoroid"
>>> with "meteor."
>>>
>>> Say what?
>>>
>>> Bob Verrish wrote an article about it:
>>> http://meteorite-recovery.tripod.com/2008/mar08.htm
>>>
>>> I quote the IAU:
>>>
>>> Definition of terms by the IAU Commission 22, 1961.
>>>
>>> A. meteor: in particular, the light phenomenon which results
>>> from the entry into the Earth's atmosphere of a solid particle
>>> from space; more generally, as a noun or an adjective, ANY
>>> PHYSICAL OBJECT or phenomenon associated with such
>>> an event.
>>>
>>> B. meteoroid: a solid object moving in interplanetary space,
>>> of a size considerably smaller than an asteroid and considerably
>>> larger than an atom or molecule.
>>>
>>> C. meteorite: any object defined under B which has reached
>>> the surface of the Earth without being completely vaporized.
>>>
>>> D. meteoric: the adjectival form pertaining to definitions A and B.
>>>
>>> E. meteoritic: the adjectival form pertaining to definition C.
>>>
>>> F. fireball: a bright meteor with luminosity which equals or
>>> exceeds that of the brightest planets.
>>>
>>> G. micrometeorite: a very small meteorite or meteoritic particle
>>> with a diameter in general less than a millimeter.
>>>
>>> Now, is everything perfectly clear?
>>>
>>> I didn't think so...
>>>
>>>
>>> Sterling K. Webb
>>> ---------------------------------------------------------------------------------------------
>>> ----- Original Message -----
>>> From: "Jason Utas" <meteoritekid at gmail.com>
>>> To: "Meteorite-list" <meteorite-list at meteoritecentral.com>
>>> Sent: Wednesday, January 13, 2010 12:49 AM
>>> Subject: Re: [meteorite-list] Small Asteroid 2010 AL30 Will Fly Past
>>> TheEarth
>>>
>>>
>>> Hello Sterling, Larry, All,
>>> Interesting - there's another problem with Sterling's initial
>>> definition, of which the following statement was a component:
>>>
>>> "2010 AL30 could be a "meteoroid" if it would hit and
>>> leave a piece to be recovered. Just be very patient and
>>> live a long time... (Always a good idea anyway.)"
>>>
>>> As per that definition, though, there's a problem when it comes to
>>> single crater-forming meteorites that don't leave pieces to be
>>> recovered. Yes, they hit the earth, but if they can't be recovered
>>> in
>>> any way, can they really be called meteorites (because they don't
>>> technically produce recoverable 'meteorites')?
>>>
>>> Admittedly that argument is only a problem if we're using the
>>> outdated
>>> version of the definition, but it raises another question.
>>>
>>> If an interplanetary object does strike the surface of the earth -
>>> and
>>> vaporizes upon impact, is it still considered a meteorite?
>>> Are craters formed by meteorites? Asteroids? I assume a meteoroid
>>> wouldn't be large enough to vaporize itself on impact, but even the
>>> faintest of shooting stars produce dust particles which will
>>> eventually reach the ground.
>>> - So there's a minimum size limit on "meteorites" - they must be
>>> larger than the dust produced by fireballs themselves (apparently),
>>> but as for crater-forming bodies...I've always simply called them
>>> meteorites because, well, in my mind, they've struck the surface of
>>> the earth, so they're meteorites.
>>> Trouble arises if the language of the currently used definition is
>>> specific enough to note that for a meteorite to be a meteorite,
>>> fragments must be recoverable. And if that's the case, then many
>>> craters were in fact formed by...Asteroids? This definition would
>>> also change on individual crater's with time, as older craters might
>>> have arrived with recoverable fragments, but such pieces could have
>>> since been lost to time and weathering (craters generally outlast
>>> meteorite fragments, after all).
>>>
>>> So...yeah. A few problems.
>>> Any thoughts?
>>>
>>> Regards,
>>> Jason
>>>
>>> On Tue, Jan 12, 2010 at 10:04 PM, <geozay at aol.com> wrote:
>>>>
>>>>
>>>>
>>>>>>"My" definition of "meteoroid" is just the standard
>>>> textbook definition. Before it hits the Earth, it's
>>>> a "meteoroid." While in fiery flight through the
>>>> atmosphere, it's a "meteor." If a piece lands on the
>>>> Earth (and somebody finds it), it's a "meteorite."<<
>>>>
>>>> I understood that a meteoroid is a small bodied natural object, in
>>>> a
>>>> separate solar orbit from that of earth's. When it enters the
>>>> earths
>>>> atmosphere
>>>> and in the incandescent phase, the visible phenomena is a meteor.
>>>> Afterwards, during the dark phase, its no longer in a separate
>>>> solar
>>>> orbit from that
>>>> of the earth's. It has yet to hit the ground to become a meteorite.
>>>> What
>>>> is this object called during the dark phase? I personally call it a
>>>> meteorite since its under the control of the earth at that point
>>>> and
>>>> not
>>>> independent of the earth. Also there has been detected by various
>>>> space probes out
>>>> around Jupiter, "meteoroids" that are too fast to be in solar orbit
>>>> and thus
>>>> of interstellar origins. Are these still called meteoroids?
>>>> GeoZay
>>>>
>>>> ______________________________________________
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>>
>>
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>
>
Received on Wed 13 Jan 2010 10:46:05 PM PST