[meteorite-list] Mars Express: Phobos Flyby Images Released

[Jerry Flaherty]

Thank you Richard [et. Alan]. I'm happy to have some corroboration for my 
perceptions. Rubble pile to the rescue!
Jerry

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From: "Richard Kowalski" <damoclid at yahoo.com>
Sent: Thursday, March 18, 2010 3:40 PM
To: "Meteorite Mailing List" <meteorite-list at meteoritecentral.com>; "Jerry 
Flaherty" <grf2 at comcast.net>
Subject: Re: [meteorite-list] Mars Express: Phobos Flyby Images Released

> A similar question came up on MPML about the grooves on Phobos. I thought 
> this answer by Alan Harris might be of interest.
>
> --
> Richard Kowalski
> Full Moon Photography
> IMCA #1081
>
>
> Alan Harris wrote:
>
> The "strings" or "grooves" have been seen since the time of the early
> Mariners and Vikings, they're just seen a little (lot) better now.  They
> are not related to multiple impacts, in spite of some appearance of being 
> strings of craters.  They have been studied extensively over the years, 
> with their nature not entirely resolved, but appear to be related in some 
> way with the tidal environment of Phobos.  If it were a fluid, it would 
> simply come apart, since it is inside the classical Roche limit.  However, 
> even a "rubble pile" can persist there, held together only by the "angle 
> of repose" limit of such material.  When struck by an impact though, the 
> vibration of the impact may allow material to "slump", just as we 
> sometimes see landslides triggered by earthquakes.  This kind of slumping 
> may result in crack or "grooves" running across the terrain.  I 
> co-authored a paper in Nature many years ago putting this hypothesis 
> forward (Soter, S., Harris, A. 1977, Are striations on PHOBOS evidence for 
> tidal stress? Nature 268, 421).  This is not the last word on the matter 
> (in fact, it was sort of the
> "first word").  There are a number of more recent publications on it.
>
> Alan
>
>
>