Posted to sci.astro:

From: rgregoryclark@yahoo.com (Robert Clark)
Newsgroups: sci.astro,alt.sci.planetary,sci.physics,sci.geo.meteorology
Subject: Polarized clouds on Mars, further evidence for liquid water in Solis Lacus, Mars?
NNTP-Posting-Host: 147.31.162.226

At the October, 2004 40th Vernadsky-Brown Conference was presented a
report that observed polarization in the refelected light from clouds
on Mars by the Hubble telescope:

35 - POLARIZATION CLOUDS IN THE MARTIAN ATMOSPHERE: HUBBLE SPACE TELESCOPE OBSERVATIONS. V. Kaydash, Yu. Shkuratov, M. Kreslavsky, G. Videen, M. Wolff, J. Bell.
The 40th Vernadsky/Brown Microsymposium on Comparative Planetology.
October 11-13, 2004, Moscow Russia
http://www.geokhi.ru/~planetology/theses/35_kaydash_et_al.pdf

Polarization of light is known to be produced by round liquid water
drops as opposed to randomly oriented multi-faceted ice crystals. The
process is described here:

Estimate of the global distribution of stratiform supercooled liquid
water clouds using the LITE lidar.
Robin J. Hogan, Mukunda D. Behera,1 Ewan J. O'Connor, and Anthony J.
Illingworth
GEOPHYSICAL RESEARCH LETTERS, VOL. 31, L05106,
doi:10.1029/2003GL018977, 2004
http://www.met.rdg.ac.uk/clouds/publications/lite_mixedphase.pdf

Depolarization ratio
http://lidar.ssec.wisc.edu/papers/pp_thes/node20.htm

The figures shown in the Vernadsky/Brown report show the clouds with
the high polarization extend over the Solis Lacus region. The
observations were taken in southern Summer on Mars in 2003. Earlier
Viking evidence had shown this seasonal period may be when water is
released in Solis Lacus:

From: Robert Clark (rgregoryclark@yahoo.com)
Subject: Will Mars Odyssey prove liquid water in Solis Lacus, Mars?
Newsgroups: sci.astro
Date: 2003-08-08 21:51:54 PST
http://groups.google.com/groups?selm=832ea96d.0308082051.54a3133b@posting.google.com

Images from Mars Express have also shown autumn clouds or fogs in
Solis that may contact the ground and form liquid water:

From: Robert Clark (rgregoryclark@yahoo.com)
Subject: Further on liquid water in Solis Lacus, Mars.
Newsgroups: sci.astro, alt.sci.planetary, sci.physics,
sci.geo.meteorology
Date: 2004-10-09 13:39:43 PST
http://groups.google.com/groups?selm=832ea96d.0410091239.537ac3c1@posting.google.com

Bob Clark