[meteorite-list] Maximum theoretical Earth impact velocity

From: Jim Wooddell <jim.wooddell_at_meteoritecentral.com>
Date: Mon, 14 Apr 2014 15:07:16 -0700
Message-ID: <534C5C14.9090509_at_suddenlink.net>

Flagstaff captured the event good enough to obtain some info. I looked
at the Los Alamos cam and like Mayhill, only flashes. The FACT cam lost
it's interent connection but is still running if someone can get there
and load a flash drive. Payon's computer was down.

Jim



On 4/14/2014 2:50 PM, Bill Cooke wrote:
> The information
>
>>> I found some info on the fall and here is some stats...
>>>
>>> vel 667.2 km/s beg 135.8 km end 40.8 km
> is from our Fireballs website and is an automatic, obviously incorrect solution to the event. There are 2 NASA cameras in southern New Mexico - one, at NMSU, collected decent data on the event, whereas the other one, located in Mayhill, saw only bright flashes through clouds, very similar to lightning. The automated software did the best it could to calculate a trajectory, but lightning events are often confused with fireballs, and it simply "went home to momma". On the plus side, we have been able to filter out most of the planes :/
>
> If you use the Fireballs website, please look at the videos. If one or more shows lightning, then you know the trajectory is crap. In general, any meteor solution with a speed higher than 72-73 km/s should be regarded with much skepticism.
>
> Most all sky meteor cameras are similar to the Sandia design and use relatively low resolution low light level cameras like the Watec 902H2. As a result, meteor trajectory precision is about 100 meters in normal cases, which translates to an uncertainty in speed of 5-10%. As mentioned by others, this affects the semimajor axis and eccenticity (size and shape of orbit) the most, with the orbital angles (inclination, argument of perihelion, and ascending node) being much better determined, usually to the 1% level. These are low precision orbits, good for statistical work, but individual examples should be used with care.
>
> Regards,
> Bill Cooke
>
> On Apr 14, 2014, at 2:54 PM, "Matson, Rob D." <ROBERT.D.MATSON at leidos.com> wrote:
>
>> Hi Chris/Shawn/All,
>>
>> There is obviously something squirrely going on in that generated orbit.
>> For one thing, look at the error bars on the velocity -- they cover all
>> possible velocities (and as Chris points out, impossible velocities as
>> well).
>>
>> I do have a comment about the oft-quoted 72 km/sec value. It is derived
>> from the orbital velocity of the earth around the sun which averages
>> 29.78 km/sec encountering a retrograde body at just below solar system
>> escape velocity, which is around 42.1 km/sec at the earth's average
>> distance from the sun. This gets you to 71.88 km/sec. However, earth's
>> maximum orbital velocity (which occurs at perihelion in early January
>> each year) is 30.29 km/sec. And solar system escape velocity at earth's
>> perihelion distance is 42.48 km/sec. So that increases the closing
>> velocity to 72.77 km/sec. However, this still isn't the theoretical
>> maximum closing velocity, since I haven't included the acceleration of
>> the intercepting body due to earth's gravity well.
>>
>> At an initial closing speed of 72.77 km/sec, there isn't a lot of time
>> for the earth's gravity to act on the body before it hits the atmosphere,
>> so the velocity boost is much smaller than earth's escape velocity (11.2
>> km/sec). From conservation of energy considerations, it can be shown
>> that the square of the impact velocity is equal to the sum of the
>> squares of the escape velocity and the approach velocity. So:
>>
>> Max impact velocity = SQRT(11.2^2 + 72.77^2) = 73.63 km/sec
>>
>> So in January, it is certainly possible to have a meteor with a
>> velocity above 73 km/sec. Anything above 73.63 would require the object
>> to have either originated outside the Solar System, or (as Chris
>> mentioned) to have been involved in a slingshot encounter with
>> another planet prior to encountering earth.
>>
>> --Rob
>>
>> -----Original Message-----
>> From: meteorite-list-bounces at meteoritecentral.com [mailto:meteorite-list-bounces at meteoritecentral.com] On Behalf Of Chris Peterson
>> Sent: Sunday, April 13, 2014 1:10 PM
>> To: meteorite-list at meteoritecentral.com
>> Subject: Re: [meteorite-list] HUGE Meteor Sighting in Cottonwood AZ - Stats from fall
>>
>> There is almost no possibility of a meteor having that speed. The maximum possible velocity a body in orbit around the Sun can encounter the Earth at is 72 km/s. Anything faster than that would exceed the solar escape velocity, implying either some sort of slingshot orbit or a body originating outside the Solar System. Only a few meteors have been observed with velocities above 72 km/s, and those only a bit more, and perhaps of questionable measurement. More are in radar data (small particles), but it has been called into question if these actually have the velocities being measured.
>>
>> Suffice to say, last night's meteor showed the characteristics of a low to medium speed parent body- something between 11 km/s and say 40 km/s.
>>
>> What is the source of the data you are using for your calculations?
>>
>> Chris
>>
>> *******************************
>> Chris L Peterson
>> Cloudbait Observatory
>> http://www.cloudbait.com
>>
>> On 4/13/2014 1:57 PM, shawnalan at meteoritefalls.com wrote:
>>> Hello Listers
>>>
>>> I found some info on the fall and here is some stats...
>>>
>>> vel 667.2 km/s beg 135.8 km end 40.8 km
>>>
>>> Now could a meteorite come from the Vel speed? I mean thats really
>>> fast 667.2km, or that could be a mistake, which I think it is? With
>>> the meteor ending at 40km there is a possibility there could be some
>>> stones on the ground. And after looking at the video I could see the
>>> meteor for around 4 seconds and at the end the meteor got brighter.
>>>
>>> more stats below...
>>>
>>> Shawn Alan
>>> IMCA 1633
>>> ebay store
>>> http://www.ebay.com/sch/imca1633nyc/m.html
>>> Meteoritefalls.com
>>>
>>>
>>> time 20140413 3.0738 hours
>>> lat 32 26 22.632 = 32.4396 deg
>>> lon 253 16 38.856 = 253.2775 deg
>>> ht 40.775 b -1.38207 7.62031 -17.37020 -7.68054
>>> alp 300.962 +/- 0.462 deg
>>> del 70.037 +/- 0.310 deg
>>> v_inf 667.240 +/- 977.292 km/s
>>> v_avg 667.240 +/- 977.292 km/s
>>>
>>> a -0.002 +/- 0.006 AU
>>> e 493.776 +/- 1444.978
>>> incl 85.761 +/- 3.793 deg
>>> omega 168.225 +/- 0.185 deg
>>> asc_node 22.922 +/- 0.000 deg
>>> v_g 667.102 +/- 977.428 km/s
>>> v_h 668.691 +/- 976.474 km/s
>>> alp_geo 301.065 +/- 0.482 deg
>>> del_geo 70.004 +/- 0.311 deg
>>> q_per 0.982 +/- 0.001 AU
>>> q_aph -0.986 +/- 0.011 AU
>>> lambda 30.964 +/- 1.513 deg
>>> beta 78.151 +/- 0.165 deg
>>> true anom 11.775 +/- 0.165 deg
>>>
>>> T_j hyp
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-- 
Jim Wooddell
jim.wooddell at suddenlink.net
http://pages.suddenlink.net/chondrule/

Received on Mon 14 Apr 2014 06:07:16 PM PDT