Thank you Richard [et. Alan]. I'm happy to have some corroboration for my
perceptions. Rubble pile to the rescue!
Jerry
--------------------------------------------------
From: "Richard Kowalski" <[email protected]>
Sent: Thursday, March 18, 2010 3:40 PM
To: "Meteorite Mailing List" <[email protected]>; "Jerry
Flaherty" <[email protected]>
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
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