Here's a link on an article on the AIM mission to study such clouds:

NASA Satellite Takes AIM at Earth's Highest Clouds

By Tariq Malik
Staff Writer
posted: 25 April 2007
http://www.space.com/businesstechnology/070425_techwed_aim.html

The article describes it as studying Polar Mesospheric Clouds, at around 85 km altitude. But perhaps it will also study Polar Stratospheric Clouds, PSC's, at around 50 km altitude.
The PSC's are interesting because they can be made up by a large portion of aqueous acid mixtures, that is, a combination of liquid water, nitric acid and sulfuric acid, and at atmospheric pressures analogous to those that hold for low lying clouds or fogs on of Mars.
For this reason I believe they provide a good model for how low lying clouds or fogs on Mars can consist partly of liquid water.

Some links on the aqueous PSC's:

Polar Stratospheric Clouds.
"Type I a (Nitric acid trihydrate particle - NAT) crystalline particles forming at 195 K,
Type I b (Supercooled ternary solution - STS) spherical liquid particles forming at 193 K,
Type II (Water ice) ice crystals forming below 188 K."
http://www.iap-kborn.de/optik/psc/psc_e.htm

Balloon-borne measurements of Polar Stratospheric Clouds.
"First results of in-situ measurements of the chemical composition of PSCs are presented, which have been performed over Kiruna, Sweden, in the early morning of January 25, 1998. PSCs at 21.5 and 23 km and temperatures between 187 and 192K have been encountered with a balloon-borne experiment, a combination of a PSC mass spectrometer and a backscatter sonde (operated by N. Larsen, Danish Meteorological Institute, Copenhagen, Denmark) [1]. In the clouds, a simultaneous increase of condensed water, nitric acid, and backscatter ratios has been observed. The measured molar ratios of water to nitric acid indicate the presence of liquid mixtures of water, nitric acid, and sulfuric acid, so-called supercooled ternary solution particles (STS)."
http://www.mpi-hd.mpg.de/mauersberger/schreiner/#Ballon..

Note the similarity in appearance between the Polar Stratospheric Clouds in the images here:

Polar Stratospheric Clouds (PSC).
http://www.iap-kborn.de/optik/psc/alomar_rmr_psc.02.htm

and the image of the clouds on Mars here:

MARTIAN STREAMERS.
What's Up in Space -- 15 Aug 2005.
(Select the archives for August 15th)
http://www.spaceweather.com/archive.php?view=1&day=15&month=08&year=2005

Bob Clark