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

From: Richard Kowalski <damoclid_at_meteoritecentral.com>
Date: Thu, 18 Mar 2010 12:40:59 -0700 (PDT)
Message-ID: <311026.12120.qm_at_web113607.mail.gq1.yahoo.com>

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
      

Received on Thu 18 Mar 2010 03:40:59 PM PDT