[meteorite-list] www.venusmeteorite.com - what are your opinions on this claim

From: Randall Gregory <randall_gregory_at_meteoritecentral.com>
Date: Wed, 14 Feb 2007 08:43:53 -0800 (PST)
Message-ID: <588307.89916.qm_at_web52103.mail.yahoo.com>

Mr. Webb,McCafferty and any interested parties on the list.
   
  If you don't mind, coud you please answer a couple of questions?
   
  Could your Martian impact scenario apply to ejecta from Mercury?
  http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1933.pdf
   
  "The spatial density (number per unit volume) of meteoroids varies as a function of distance from the sun, distance from a planet, ecliptic latitude and longitude" Are there any projections on the total number of spatial meteoroids related to planetary volume?
   
  Do meteoroids tend to group or stream? Or are streams and groupings a rare occurrence?
  Excluding space dust, my feelings are that streams and groups would be predominant.
   
  Due to a lower escape velocity, would a large asteroid impact on Mercury close to it's aphelion be more likely to produce ejecta reaching the escape velocities of Mercury/Sun than a similar event on Venus? Any probability studies?
   
  (For probability, I would assume the best/worst possible conditions: equatorial launch, launch relative to planetary rotation, lowest daily temperature range, and rock composition/density (basaltic mass).
   
  Do you know of any studies with respect to meteoroids in space arriving to earth as meteorites, do they have totally random trajectories due to collisions or would they generally follow a straight course from their home asteroid/planet? To put it quite simply, depending on rotation, impact time, solar orientation, and impact angle could ejecta from a the inner planets travel in a relatively straight line away from the sun. And would this same scenario apply to planets outside earth's orbit. Could they travel in a similar fashion towards Earth? And could this relate to the Earth's orientation to the sun at the time of meteroite impact. In other words, would outer planet meteroids be more likely to fall at night and inner planet meteorids fall during the day.
   
  Is fusion crust thickness directly related to the mineral characteristics of density, hardness, melting point, thermal conductivity, and internal tempurature of the meteoroid? Am I wrong in assuming that it is? Are there other factors?
   
  Would a shock-heated ejecta upon encountering the extreme cold of space cause any changes in the density of the underlying material? What about ejecta at melt temperature?
   
  What would be the effect on micrometeorite pitting on various meteoroids?
   
  "Interplanetary dust particles (micro-meteoroids) were expected to form well-defined craters upon impacting exposed material in space. Studying the frequency and features of these craters will provide data on the mass-flux distribution of micro-meteoroids and, to a lesser extent, on the velocity, magnitude and direction" - Study of Meteoroid Impact Craters on Various Materials, NASA Langley Research Center.
   
  Some of my samples show pitting which may be caused by micro-meteoroid collisions. Due to the extreme hardness of the sample and sub-millimeter thickness of the fusion crust these pits have been preserved. The ablated material gathers on the trailing edge of these pits on orientated samples.
   
  Do you know of any meteorites currently in collections that exhibit pitting? What are the characteristics of the ablated material?
   
  Are all meteorites tested for density and most specifically hardness?
   
  And could anyone please help me retrieve this article:
   
  author = {{Blanchard}, M.~B.},
    title = "{Artificial Meteor Ablation Studies}",
booktitle = {IAU Colloq. 13: Evolutionary and Physical Properties of Meteoroids},
     year = 1973,
   editor = {{Hemenway}, C.~L. and {Millman}, P.~M. and {Cook}, A.~F.},
    pages = {241-+},
   adsurl = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1973eppm.coll..241B&db_key=AST},
  adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System
   
   
  Randall
   
   
   
  Rob,
   
  I was wondering if there would there be any ablation at all on the outbound martian rock, from a planet with:
   
  Surface atmospheric pressure: ~6.1 mb (about 1/150th that of Earth's)
Surface gas density: ~0.020 kg/m3

  Surface temperature: ~210 K (-63 degrees Celsius)
  Low escape velocity
   
  And is it possible to achieve such a low impact angle or would gravity and aerodynamic drag increase the angle so that a 1-3 degree trajectory may not be possible. I believe existing ballistic models could be combined with a Mars atmosphere model and gravitational model that might help to answer this question.
   
  Quite possibly a composite mathematical model borrowing code from the many existing models might add validity to your theory. I believe Mars atmosphere models, ballistic, compression, heating, and the myriad are all fairly constant. It might not be such a large undertaking to help determine if a lightly shocked rock could be back-spinned into space. I'd really like to see a model like this applied to the other planets such as Mercury.
   
  Would anyone like to start a project on this?
   
  In your estimation, could one determine what the minimum energy values are needed for this event to occur? And could this model be applied to Mercury? ;)
   
  Randall

Rob McCafferty <rob_mccafferty at yahoo.com> wrote:
  
--- "Sterling K. Webb"
wrote:

> [I have a theory, of course, but not room enough
> in this margin to write it down.]
>


I believe Fermat wrote something the same thing and it
took nearly 300 years to prove it. Sterling, make a
mental note to ACTUALLY write the theory down to save
some poor sucker from having to write a 200page thesis
in the future.

Would not Martian ablation on the way out from Mars
simply be destroyed by terrestrial ablation on the way
in to us? You know how much of the meteorites are
removed by the process. I find it difficult to believe
any could survive.

I often thought that rock could escape it's host
planet through the rarefaction zone above the
impactors trajectory. However, how this tallies with
low shock levels I don't know.
As I understand, the low shock would need to be right
at the very edge of the impact site. Not ideal for
launching up into a rarefaction zone. ...

Unless, {and here's a wild guess that's probably WAAAY
off but I'll accept criticism with dignity, only a
little sobbing and wailing}...

Could a low angle impact [1-3degrees] produce
sufficient rarefaction befind it to allow the low
shocked rock at the trailing edge of the impact site
to be 'grazed off' in a backward direction, back up
the initial path of the impactor?

Rob McC



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Received on Wed 14 Feb 2007 11:43:53 AM PST