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(meteorobs) Fw: [meteorite-list] Meteor Excites Night Skies Over Colorado
----- Original Message -----
From: Ron Baalke <baalke@zagami.jpl.nasadot gov>
To: Meteorite Mailing List <meteorite-list@meteoritecentral.com>
Sent: Sunday, August 26, 2001 9:11 PM
Subject: [meteorite-list] Meteor Excites Night Skies Over Colorado
>
>
>
http://www.zwire.com/news/newsstory.cfm?newsid=2264796&title=Meteor%20excite
s%20night%20skies&BRD=1190&PAG=461&CATNAME=Top%20Stories&CATEGORYID=410
>
> Meteor excites night skies
> Valley Courier
> August 24, 2001
>
> SAN LUIS VALLEY - A very bright, orange-white
> meteor lit up skies over a large portion of central and eastern Colorado
on
> August 17 at 10:44 p.m.
>
> Many people called television stations or law enforcement agencies
thinking
> a plane had crashed and started a forest fire.
>
> Calls to the meteorite research team at the Denver Museum of Nature &
> Science overloaded phone lines and e-mails.
>
> More than 400 calls were taken over three days from locations in all
corners
> of Colorado including Grand Junction, Alamosa, Fort Collins and Colorado
> Springs, thus giving the museum information about the point in the sky
where
> the fall terminated.
>
> The museum's main goal in this endeavor is to answer media requests, be an
> educational resource, and to eventually locate meteorites on the ground.
>
> Search underway for witnesses, pieces
>
> The museum is in contact with Forest Service officials in the area to
> emphasize that meteorites, if found, are the property of the land owner.
>
> Meteorites found on private property belong to the land owner and if found
> on government property the Smithsonian Institution is the custodian of
those
> specimens.
>
> For the Colorado fireball Friday night, most people were particularly
> impressed with two aspects: the steep downward angle of descent; and the
> dazzling brilliance accompanied by sparks.
>
> Museum investigators were amazed that loud sonic booms or explosive sounds
> were not readily heard by observers.
>
> It appears that the lack of these phenomena is related to the steep
descent.
>
> The meteor was seen as far away as New Mexico, Wyoming, Idaho, Nebraska
and
> Kansas.
>
> It mainly was spotted by late night travelers facing southwestern
Colorado.
>
> As far as is known no one captured the event on video but people with
> security cameras or banks with ATM cameras should check if they have tapes
> from that Friday night.
>
> The museum now has sufficient information to preliminary locate the
general
> area of the fireball over south central Colorado.
>
> It is most likely in the southern Rio Grande National Forest area in
Conejos
> County, a rugged, forested region in the southeastern part of the San Juan
> Mountains.
>
> At this time there is no evidence of meteorites on the ground in south
> central Colorado or in the Conejos area and no ground search is being
> conducted.
>
> However, museum field research staff will likely travel to the Monte Vista
> area and interview witnesses.
>
> Anyone who has specific information which could lead to a compass bearing
> for the meteor may contact the Denver Museum of Nature & Science,
> 303-370-6445; jmurphy@dmns.org
>
> Dr. Jack Murphy, curator of geology at the museum, said eye witnesses need
> to be "sober and stationary" so they can give a more exact location for
the
> occurrence.
>
> The museum research team, consisting largely of volunteers, will still
have
> to do exacting field work to locate meteorites if they fell, unless
someone
> coincidentally finds a meteorite or locates a fresh hole through the roof
of
> a building.
>
> Specific compass bearings and measurements of the altitude of the breakup
> point above the horizon from different locations are essential to map a
> meteorite fall.
>
> The museum team has investigated other Colorado fireballs and informed
> communities of the chances of locating meteorites.
>
> New ways to look at it
>
> Because the meteor was so bright, people automatically thought it was
closer
> to them than it actually was.
>
> In addition to the witness accounts, the museum now has data from a
> sophisticated sound detection system in Los Alamos, N.M., that has located
> the atmospheric position of the fireball over the eastern San Juan
> Mountains.
>
> The data from Los Alamos National Laboratories, from Dr. Peter Brown "...
is
> around 50 Tonnes TNT equivalent yield which for a nominal 18 km/sec entry
> velocity suggests an entry mass of over a metric tonne." This velocity is
> the same as 11.25 miles per second.
>
> Depending on initial mass and velocity, most meteors arrive into the
earth's
> orbit at a velocity as high as 26 miles per second, then their speeds drop
> off during entry between 10 miles per second and 26 miles per second,
> according to Richard Norton in Rocks from Space.
>
> They begin giving off light in the upper atmosphere and flare very bright
as
> friction increases during descent.
>
> Dr. Brown estimates the peak magnitude for the Friday, August 17, event to
> be around -17 to -18 on the astronomical magnitude scale. As a comparison,
> the full moon is approximately -13 magnitude brightness, so the fireball
> works out to be about 40 times more bright than a full moon according to
> Larry Sessions, North American Skies (www.webcom.com/safezone/nas).
>
> Not your typical event
>
> The Aug. 17 fireball was not a typical event compared to what the museum
> team has investigated before.
>
> A "typical" meteor event was determined from data taken from a camera
survey
> of 44 meteors by Halliday and others (1989.)
>
> Meteors detected in the cameras probably impacted the earth after 4
seconds
> of luminous atmospheric display and produce .2 to 24 pounds (.1 kg to
11kg)
> of meteoric material.
>
> The atmospheric displays began at about 39 to 58 miles (59 to 92.7 km)
above
> the earth's surface with a velocity of about 7 to 17 miles/second (11.2 to
> 27.9 km), and ended at about 19.3 miles (31 km) above the earth's surface
> with a velocity of about 5 miles/sec (8km/sec).
>
> The process the research team uses to locate the position of fireballs is
> more efficient now with the internet.
>
> Many people in Colorado are interested and knowledgeable about fireballs
and
> meteorites as evidenced by the high quality of data received at the
museum.
>
> The museum attributes this to experience in the last few years
investigating
> other similar meteors.
>
> In addition, a program of networked cameras is in the works that will view
> and record the day and night sky in an effort to more easily triangulate a
> meteor's trajectory.
>
> This All Sky Camera Network is collaboration between the museum and a team
> of Colorado teachers.
>
> The programs that are developed during the planning year will then be used
> by students statewide. (For more information on the All Sky Camera Network
> contact Gianna Sullivan, community liaison of Denver Museum of Nature &
> Science, 303-370-6097, gsullivan@dmns.org).
>
> Definitions
>
> Following are some of the definitions differentiating meteors, meteoroids
> and meteorites:
>
> Meteor: the bright light in the lower reaches of the atmosphere created
from
> friction on a falling solid mass, usually reserved for natural objects
such
> as rocks from space that are thought to originate in the Asteroid Belt
> between Jupiter and Mars.
>
> Meteoroid: the name for a natural piece of rock from space, probably a
piece
> of asteroid, that is attracted by Earth's gravity and descends through the
> atmosphere at a high rate of speed.
>
> Meteorite: the solid stony or iron material that survives flight through
the
> atmosphere and lands on the ground. Meteorites should be collected as soon
> as possible for chemical tests that can ascertain its composition and age.
>
> Check out the new Meteorite Central logo wear at
http://wwwdot cafepress.com/cp/store/store.aspx?storeid=meteorites
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