[meteorite-list] FW: Mars Odyssey THEMIS Images: July 11-15, 2005

From: Sterling K. Webb <kelly_at_meteoritecentral.com>
Date: Sat Jul 16 23:35:14 2005
Message-ID: <42D9D1CD.351F99CF_at_bhil.com>

Hi,

    Everybody seems to agree on twin impactors. Twin impactors are no mystery.
Many binary asteroids have been identified.
    There are large asteroids with much smaller "moons" of their own (like Ida
and Dactyl) and asteroids where the two bodies are very similar in size size,
including very close binaries, even ones where it is possible that the two
bodies are actually touching each other as they revolve around each other.
Contact binaries, they're called.
    They are a small minority of asteroids, of course, but there have been a
good number identified. I would think a contact binary would be a good candidate
for the origin of these two similarly sized joint craters.
    I was impressed at how clean and fresh these craters look, the one on the
right particularly. They cannot be very ancient, despite the signs of a few
small impacts on their inner walls..
    They retain their deep conical shape, the shape of the blast cone, a
characteristic mark of a fresh crater. There is little debris accumulated on
their "floors," and their inner walls are remarkably uneroded and uniform.
    I see no reference as to their size on the page, but I get the impression
that they are bigger than, for example, Arizona's Meteor Crater, perhaps 1 to 3
miles in diameter (each).
    The "left" impactor seems to have been the smaller of the two, and the
triangular shadow in the left crater seems to indicate that the left rim of that
crater is elevated to a peak at the far side.
    Binaries, no doubt.


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








Marc Fries wrote:

> I didn't see what everyone else said, but to me it has to be the result of
> the simultaneous impact of two impactors. The material thrown out
> perpendicular to a line between the centers of the two craters would be
> due to the overlapping/disrupting shock waves. If the two craters formed
> at different times then the ejecta from one would just overlay the older
> crater. Great pic!
>
> Cheers,
> MDF
>
> > Hello List,
> >
> > Any ideas as to what went on here? Check #60 - one of the MOST unusual
> > crater formations I have ever seen.
> >
> > All the best,
> >
> > Greg
> >
> > Greg Redfern
> > NASA JPL Solar System Ambassador
> > http://www2.jpl.nasa.gov/ambassador/index.html
> > What's Up: The Space Place
> > http://www.wtopnews.com/index.php?nid=421
> >
> >
> > o THEMIS Images as Art #60 (Released 15 July 2005)
> > http://themis.la.asu.edu/zoom-20050715A.html
> >
> >
> >
> >
> > All of the THEMIS images are archived here:
> >
> > http://themis.la.asu.edu/latest.html
> >
> > NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission
> > for NASA's Office of Space Science, Washington, D.C. The Thermal Emission
> > Imaging System (THEMIS) was developed by Arizona State University,
> > Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing.
> > The THEMIS investigation is led by Dr. Philip Christensen at Arizona State
> > University. Lockheed Martin Astronautics, Denver, is the prime contractor
> > for the Odyssey project, and developed and built the orbiter. Mission
> > operations are conducted jointly from Lockheed Martin and from JPL, a
> > division of the California Institute of Technology in Pasadena.
> >
> >
> >
> > To remove yourself from all mailings from NASA Jet Propulsion Labratory,
> > please go to http://www.kintera.org/TR.asp?ID=M69947285956903916642665
> >
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>
> --
> Marc Fries
> Postdoctoral Research Associate
> Carnegie Institution of Washington
> Geophysical Laboratory
> 5251 Broad Branch Rd. NW
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Received on Sat 16 Jul 2005 11:34:38 PM PDT