RE: Natural Satellites

From: Matson, Robert (ROBERT.D.MATSON@saic.com)
Date: Fri Jun 09 2000 - 11:26:50 PDT

  • Next message: Allen Thomson: "Re: Natural Satellites"

    Hi All,
    
    I was going to answer Patrick's question about captured
    natural satellites, but Frank's reply was excellent.  It
    covers the basic problem -- explaining why asteroid capture
    is virtually impossible as a 2-body problem -- but even
    better, it discusses an extremely rare case where it could
    happen (if only briefly):
    
    > But what if the asteroid passes very close to the Earth and enters the
    upper 
    > atmosphere? Friction and atmospheric pressure ... can irreversibly reduce
    > the energy of the meteor. Usually this ends with the meteor[oid] entering
    the
    > lower atmosphere and burning up. But it's also possible for a meteor[oid]
    to
    > skip out of the atmosphere. In that case, you would have an object with a
    > speed quite possibly reduced below Earth's escape velocity. ...
    > Unfortunately, the perigee of the bound orbit would necessarily be located
    > at the point in the atmosphere where the moonlet experienced its
    deceleration.
    > ... The moonlet would almost certainly enter on the next orbit and be
    > destroyed in the atmosphere.
    
    For those who weren't aware, this exact scenario actually played
    itself out less than four years ago.  A meteoroid first entered
    Earth's atmosphere around 8 pm MDT on October 3, 1996, east of
    Las Cruces, NM, heading east-northeast on a very shallow trajectory.
    Aerodynamic forces began to break it apart as it crossed over the
    Texas Panhandle, showering the area with a brilliant meteor display.
    However, the main fragment retained sufficient momentum to continue
    back out of the atmosphere (greatly decelerated).  Its velocity
    reduced from >40,000 mph to ~18,000 mph, the meteoroid went into
    Earth orbit.  100 minutes later, the meteoroid entered the atmosphere
    a second time, this time for good.  It crossed the California
    coastline near Point Conception, passed just north of Bakersfield
    and reentered somewhere northeast of Kernville -- possibly as far
    as Owens Valley.  Sonic booms were heard throughout the area.
    Unfortunately, meteorites from this fall have yet to be found.
    
    --Rob
    
    -----------------------------------------------------------------
    Unsubscribe from SeeSat-L by sending a message with 'unsubscribe'
    in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org
    http://www2.satellite.eu.org/seesat/seesatindex.html
    



    This archive was generated by hypermail 2b29 : Fri Jun 09 2000 - 11:25:32 PDT