[meteorite-list] Meteorites 101

From: lebofsky at lpl.arizona.edu <lebofsky_at_meteoritecentral.com>
Date: Sun, 16 Jan 2011 16:08:07 -0700 (MST)
Message-ID: <a189422fe60eaa1118fe1ca43b4d4f69.squirrel_at_webmail.lpl.arizona.edu>

Jonathan:

The mass of the region between Mars and Jupiter is dominated by the larger
objects, so it is a belt of asteroids, an asteroid belt.

Larry

> Barrett,
> So is the "Asteroid Belt" actually;
> a "Meteriod Belt", an "Asteriod Belt", or a "Satellite Belt" ? ;~}
> Jonathan
>
>
>
> ----- Original Message -----
> From: "Barrett" <BarrettWF at comcast.net>
> To: <Meteorite-list at meteoritecentral.com>
> Sent: Saturday, January 15, 2011 5:29 PM
> Subject: [meteorite-list] Meteorites 101
>
>
>>
>> The definitive source WIKIPEDIA!! Says;
>>
>> MeteoroidThe current official definition of a meteoroid from the
>> International Astronomical Union is "a solid object moving in
>> interplanetary space, of a size considerably smaller than an asteroid
>> and
>> considerably larger than an atom".[1][2] Beech and Steel, writing in
>> Quarterly Journal of the Royal Astronomical Society, proposed a new
>> definition where a meteoroid is between 100 ??m and 10 m across.[3] The
>> NEO
>> definition includes larger objects, up to 50 m in diameter, in this
>> category. Very small meteoroids are known as micrometeoroids (see also
>> interplanetary dust).
>>
>> The composition of meteoroids can be determined as they pass through
>> Earth's atmosphere from their trajectories and the light spectra of the
>> resulting meteor. Their effects on radio signals also give information,
>> especially useful for daytime meteors which are otherwise very difficult
>> to observe. From these trajectory measurements, meteoroids have been
>> found
>> to have many different orbits, some clustering in streams (see Meteor
>> showers) often associated with a parent comet, others apparently
>> sporadic.
>> Debris from meteoroid streams may eventually be scattered into other
>> orbits. The light spectra, combined with trajectory and light curve
>> measurements, have yielded various compositions and densities, ranging
>> from fragile snowball-like objects with density about a quarter that of
>> ice,[4] to nickel-iron rich dense rocks.
>>
>> Meteoroids travel around the Sun in a variety of orbits and at various
>> velocities. The fastest ones move at about 26 miles per second (42
>> kilometers per second) through space in the vicinity of Earth's orbit.
>> The
>> Earth travels at about 18 miles per second (29 kilometers per second).
>> Thus, when meteoroids meet the Earth's atmosphere head-on (which would
>> only occur if the meteors were in a retrograde orbit), the combined
>> speed
>> may reach about 44 miles per second (71 kilometers per second).
>>
>> Meteor"Meteor" and "Meteors" redirect here. For other uses, see Meteor
>> (disambiguation).
>> See also Hydrometeor.
>>
>> Comet 17P/Holmes and GeminidA meteor is the visible path of a meteoroid
>> that has entered the Earth's atmosphere. Meteors typically occur in the
>> mesosphere, and most range in altitude from 75 km to 100 km.[5] Millions
>> of meteors occur in the Earth's atmosphere every day. Most meteoroids
>> that
>> cause meteors are about the size of a pebble. They become visible
>> between
>> about 40 and 75 miles (65 and 120 kilometers) above the Earth. They
>> disintegrate at altitudes of 30 to 60 miles (50 to 95 kilometers).
>> Meteors
>> have roughly a fifty percent chance of a daylight (or near daylight)
>> collision with the Earth as the Earth orbits in the direction of roughly
>> west at noon.[clarification needed] Most meteors are, however, observed
>> at
>> night as low light conditions allow fainter meteors to be observed.
>>
>> For bodies with a size scale larger than the atmospheric mean free path
>> (10 cm to several metres)[clarification needed] the visibility is due to
>> the atmospheric ram pressure (not friction) that heats the meteoroid so
>> that it glows and creates a shining trail of gases and melted meteoroid
>> particles. The gases include vaporized meteoroid material and
>> atmospheric
>> gases that heat up when the meteoroid passes through the atmosphere.
>> Most
>> meteors glow for about a second. A relatively small percentage of
>> meteoroids hit the Earth's atmosphere and then pass out again: these are
>> termed Earth-grazing fireballs (for example The Great Daylight 1972
>> Fireball).
>>
>> Meteors may occur in showers, which arise when the Earth passes through
>> a
>> trail of debris left by a comet, or as "random" or "sporadic" meteors,
>> not
>> associated with a specific single cause. A number of specific meteors
>> have
>> been observed, largely by members of the public and largely by accident,
>> but with enough detail that orbits of the incoming meteors or meteorites
>> have been calculated. All of them came from orbits from the vicinity of
>> the asteroid belt.[6]
>>
>> FireballA fireball is a brighter-than-usual meteor. The International
>> Astronomical Union defines a fireball as "a meteor brighter than any of
>> the planets" (magnitude -4 or greater).[7] The International Meteor
>> Organization (an amateur organization that studies meteors) has a more
>> rigid definition. It defines a fireball as a meteor that would have a
>> magnitude of -3 or brighter if seen at zenith. This definition corrects
>> for the greater distance between an observer and a meteor near the
>> horizon. For example, a meteor of magnitude -1 at 5 degrees above the
>> horizon would be classified as a fireball because if the observer had
>> been
>> directly below the meteor it would have appeared as magnitude -6.[8]
>>
>> Bolide
>> An especially bright meteor, a bolide (in astronomy)"Bolide" redirects
>> here. For the Swedish guided missile BOLIDE, see RBS 70.
>> In astronomy
>> 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.[9]
>> Astronomers tend to use the term to mean an exceptionally bright
>> fireball,
>> particularly one that explodes (sometimes called a detonating fireball).
>>
>> In geology
>> Geologists use the term "bolide" more often than astronomers do: in
>> geology it indicates 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, for example".[10]
>>
>> SuperbolideIf the magnitude of a bolide reaches -17 or brighter it is
>> known as a superbolide.[9][11]
>>
>> MeteoriteMain article: meteorite
>> A meteorite is a portion of a meteoroid or asteroid that survives its
>> passage through the atmosphere and impact with the ground without being
>> destroyed.[12] Meteorites are sometimes, but not always, found in
>> association with hypervelocity impact craters; during energetic
>> collisions, the entire impactor may be vaporized, leaving no meteorites.
>>
>> TektiteMain article: tektite
>>
>> Two tektitesMolten terrestrial material "splashed" from a meteorite
>> impact
>> crater can cool and solidify into an object known as a tektite. These
>> are
>> often mistaken for meteorites.
>>
>> Meteoric dustMost meteoroids burn up when they enter the atmosphere. The
>> left-over debris is called meteoric dust or just meteor dust. Meteor
>> dust
>> particles can persist in the atmosphere for up to several months. These
>> particles might affect climate, both by scattering electromagnetic
>> radiation and by catalyzing chemical reactions in the upper
>> atmosphere.[13]
>>
>> Does this help any? Seems about correct.
>> -Barrett
>>
>> -----Original Message-----
>> From: meteorite-list-bounces at meteoritecentral.com
>> [mailto:meteorite-list-bounces at meteoritecentral.com] On Behalf Of
>> GeoZay at aol.com
>> Sent: Saturday, January 15, 2011 5:59 PM
>> To: meteorite-list at meteoritecentral.com
>> Subject: Re: [meteorite-list] Meteorites 101
>>
>>
>>>>Bolide is a term that it's good to avoid. It doesn't mean anything...
>>>> or
>> rather, it means too many different things. "Fireball" unambiguously
>> means
>> a
>> meteor of a specific apparent brightness. "Bolide" is simply
>> confusing.<<
>>
>>
>>
>> I usually think of a fireball as a meteor with a magnitude brighter
>> than
>> -3. I also sometimes think of a Bolide as being a fireball that has
>> produced
>> a sonic boom as well.
>> GeoZay
>>
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Received on Sun 16 Jan 2011 06:08:07 PM PST