Here's one report on research on static electricity that might occur
in Martian soil:

======================================
Title: Electrical Properties of Martian Regolith Simulant Particles.
Authors: Calle, C. I.; Kim, H. S.
Affiliation: AA(Sweet Briar College), AB(NASA/Kennedy Space Center)
Journal: American Astronomical Society Meeting #193, #96.07
Publication Date: 12/1998
Origin: AAS
Abstract Copyright: (c) 1998: American Astronomical Society
Bibliographic Code: 1998AAS...193.9607C

Abstract
Hubble Space Telescope observations of Mars from Earth as well as
spacecraft measurements from orbit around Mars and from the Martian surface
itself have shown that suspended dust is a significant component of the Martian
atmosphere.
Dust clouds have been observed extending over areas as large as a few
million square kilometers. Hubble has also photographed planet-wide dust
storms lasting for over one month. These conditions, coupled with the absence of any
significant amounts of water in the Martian atmosphere, may create
electrostatic potentials that could be hazardous for astronauts and equipment in
future missions. The electrical properties of the Martian soil have been
determined directly only by radio occultation from spacecraft in orbit about
Mars, by earth-based radar, and by microwave radiometry. For the present work,
experiments were designed to determine the electrical properties of a
Martian regolith simulant prepared from Andesitic rocks by NASA Johnson Space
Center that has been shown to be a good spectral analog to the soil in the
bright regions of Mars. The volume electrical conductivity of the simulant
was measured to be intermediate between that of a good conductor and that of a
good insulator. Thus, the simulant particles were expected to exhibit
fairly high surface electrostatic charging and polarizability. Experiments to
determine polarization and electrostatic charging of the simulant particles
under several conditions were conducted.
=======================================

IF it is static electricity that is causing the stickiness then to
get samples to be delivered to the Mars Phoenix instruments we might
try to take the samples when the moisture in the air is highest.
The Mars MER rovers found there was frost deposited at night that
burned off in early morning. This time would likely be when the
humidity was highest at those sites.
The Mars Phoenix site is in a polar region during Martian northern
summer where the Sun is always above the horizon so strickly speaking
there won't be *night-time* frost deposition. Still there is great air
temperature variation from -30C to -80C so there will likely be a
diurnal time frame when the frost deposition is highest and also an
optimal time frame where this frost will burn off as the temperature
rises. Note also that orbital observations show that atmospheric water
vapor is highest in the Mars polar regions so such frost deposition at
the Phoenix site might be signicantly higher than for the equatorial
MER rovers.
However, it is not certain that static electricity due to low air
moisture is the problem here. Conceivably it might be the exact
opposite where residual *liquid* water in the soil contributes to the
stickiness of the soil. If this is the case then we will actually want
to take the samples when the himidity in the air is lowest. Both
scenarios should be tried.
Still another possibility is the magnetite particles that have been
seen at the other landing sites is the cause of the stickiness. If
this is the case I doubt that humidity variations will have an effect
on the stickiness. I don't have a solution in this case. Perhaps
experiments with Mars similants containing such magnetic particles
would provide a solution about how best to deliver samples to the
lander experiments.

Bob Clark