[meteorite-list] Stardust Flyby Images of Comet Wild 2

From: Sterling K. Webb <kelly_at_meteoritecentral.com>
Date: Thu Apr 22 10:32:00 2004
Message-ID: <3FFD8901.B2EBBFF2_at_bhil.com>

     Hi,

         A comet is presumed to have spent most of its billions of years out in
     the cold beyond the planets. Something -- a gravitational encounter --
     disturbs its orbit and it falls into the inner system, probably by stages,
     with Jupiter as a big player in this game.
         Once a comet reaches an orbit in the inner system, it's pretty much
     doomed. Survival times for a icy body in the inner system is limited to a
     few hundred thousand years at most. Of course, once all the volatiles are
     gone, a rocky, dusty and much smaller body may remain to be mistaken for an
     asteroid.
         This has happened, that an "asteroid" suddenly develops a weak coma, or
     a comet loses it coma and is seen as an asteroid. Asteroid 1979VA turned out
     to be Comet Wilson-Harrington 194 III, lost and rediscovered as an
     "asteroid."
         The Zodaical Light is produced by trillions of tons of dust in the inner
     system orbital plane. This dust would be rapidly (~50,000 years) dissipated
     if it were not constantly being re-supplied from somewhere. Comets are good
     bet.
         A good case has been made for Comet Enke and assorted other large bodies
     in the inner system to be the breakup products of a very large comet (70
     km.) that got trapped in the inner system only 50,000 to 100,000 years ago.
     Tracing the evolution of the orbits of these bodies backwards for that
     length of time puts them all in the same orbit originally.
         Now, that would nice to watch! A 100 kilometer comet in an inner system
     orbit, what a show!


     Sterling K. Webb
     ---------------------------------------------------------------------

     joseph_town_at_att.net wrote:

          Hi all,

          I know I should research this myself but I hope I can get a
          relatively brief
          answer upon which I can look further into this question if deemed
          worthwhile.
          How does a small object like a comet, especially, travel for
          billions of
          years constantly venting and releasing matter continue to exist?
          Why doesn't
          it dissipate into virtual nothingness?

          Bill Kieskowski


     Sterling K. Web wrote:

> Hi,
>
> I was fascinated by the first flyby image that was
> released (the one featured on APOD). Despite its generally
> fuzzy appearance, there is a lot of detail buried in there
> that I hope we'll get to see when the wizards are through
> massaging the images for detail and content.
> I took a copy of that image and squeezed it as hard as I
> could. I doubled the spacing of all the pixels and filled in
> the intermediate spaces with eight-way median values, twiddled
> with its histogram to re-distribute the greyscale values to a
> more normal distribution, then stomped all over it with a
> square sharpness filter.
> I found that is LOTS of detail there, although my
> ham-handed efforts left some messy artifacts. For example, the
> "crater-like" circular features do not have uniformly shaded
> bottoms. They're not smooth (nor flat I would guess), but
> usually show a single deep dark conoid pit that's probably a
> large primary vent for outgassing.
> The walls of these "crater-like" features show some linear
> features, as if the depressions had formed by a slump-like
> collapse, perhaps from the rapid removal of material from
> beneath the "slump" by outgassing. Lots of tantalizing
> features not quite sharp enough to interpret. I'm left with
> the impression of a surface with lots of varying contours.
> Many of the smaller high contrast features seem to be
> albedo-related, as if between light and dark materials,
> perhaps at smaller "un-slumped" vents.
> If anyone's interested, you can view this roughly enhanced
> image at:
> <http://www.bhil.com/~kelly/wild2.html>.
>
>
> Sterling K. Webb
>
     ---------------------------------------------------------------------------
>
> Ron Baalke wrote:
>
> I've added an animation of the Comet Wild 2 flyby
> images taken by
> Stardust to the Stardust website.
> Included is a chart from the Dust Flux Instrument
> showing
> the particle impacts on the spacecraft during the
> flyby, and
> another chart showing the spacecraft thruster
> activity:
>
> http://stardust.jpl.nasa.gov/news/status/040106.html
>
> You can view the animation directly from here:
>
> http://stardust.jpl.nasa.gov/images/w2_flyby1.gif
>
> Ron Baalke
>
>
Received on Thu 08 Jan 2004 11:44:50 AM PST