It is interesting that the maps show hydrogen-rich areas west of the
Tharsis volcanoes Arsia and Pavonis Mons and west of Olympus Mons.
James Head et.al. argue that lobate flows off the western flanks of
these volcanoes suggest former glaciers there which could persist in
the form of rock glaciers or relict ice:

OLYMPUS MONS FAN SHAPED DEPOSIT MORPHOLOGY: EVIDENCE FOR DEBRIS
GLACIERS.
S. M. Milkovich and J. W. Head, III, Dept of Geological Sciences,
Brown University, Providence, RI 02912. Sarah_Milkovich@*****.edu
Sixth International Conference on Mars (2003) 3149.pdf
http://www.lpi.usra.edu/meetings/sixthmars2003/pdf/3149.pdf

COLD-BASED MOUNTAIN GLACIERS ON MARS: WESTERN ARSIA MONS FAN-SHAPED
DEPOSITS: J.W. Head1 and D.R. Marchant2; 1Dept. of Geol. Sci., Brown
Univ., Providence, RI 02912 USA; 2Dept. of Earth Sciences, Boston
Univ., Boston, MA 02215 USA.
Lunar and Planetary Science XXXIV (2003) 1247.pdf
"The sharp ridges at the head of major lobes on Arsia Mons imply
active flow and suggest the presence of buried glacier ice [4]."
http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1247.pdf

PAVONIS MONS FAN-SHAPED DEPOSITS — SMOOTH TERRAIN SURFACE ICE
DEPOSITS.
D. E. Shean1 and J. W. Head1, 1Brown University,
David_Shean@*****.edu, James_Head@*****.edu
Lunar and Planetary Science XXXIV (2003) 1154.pdf
"Elsewhere, we have presented evidence supporting a cold-based glacial
origin for the Pavonis deposits [3]. Here, we present evidence
suggesting that the smooth facies represents residual ice deposits
that have persisted until the present."
...
"We interpret the smooth terrain to be dust-covered residual ice from
the last major Pavonis Mons ice sheet. Under current martian climatic
conditions, water
ice may theoretically be stable at the surface within the Tharsis rise
due to the low thermal inertia of the soil and the lower mean annual
temperature of the region [9]. The proposed ice sheet could have
formed during periods of high obliquity [10] where equatorial regions
receive less solar insulation than the poles and can become cold traps
[11]. Excess water in the atmosphere would be deposited at low
latitudes, resulting in significant equatorial ice accumulations. The
stability of water ice at the surface is only increased with greater
burial depth, and the smooth terrain is covered by dunes that appear
to be tens of meters high. The smooth facies is of the order of
hundreds of meters thick at present and this suggests that a
significant ice component remains in the near surface today. Thus, the
Pavonis Mons fan-shaped deposits could be a site where hundreds of
millions of years-old glacial ice could be sampled during future
exploration."
http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1154.pdf

They also mention this would be consistent with the GRS hydrogen
readings:

Microsymposium 36, MS086, 2002
COLD BASED GLACIAL ORIGIN OF THE PAVONIS MONS LOBATE DEPOSITS.
D. E. Shean1 and J.W. Head2,
1Brown University, David_Shean@Brown.edu, 2Brown University,
James_Head@****.edu
http://www.planetary.brown.edu/planetary/documents/Micro_36/Abstracts/086_Shean_Head.pdf

Also notable are the high hydrogen readings in and around Valles
Marineris. It has been noted since Viking that in Noctis Labyrinthus,
part of the Marineris valley system, there are frequently seen low
lying fogs and clouds:

------------------------------------------------------------
NASA SP-441: VIKING ORBITER VIEWS OF MARS
------------------------------------------------------------
- THE ATMOSPHERE -
"Early Morning Clouds in the Tharsis Montes and Valles Marineris
Region. Ascraeus Mons and Pavonis Mons are prominently displayed in
this mosaic, and dense cloud blankets cling to their northern slopes.
High cirrus clouds lie to the west of Tharsis, and waves are visible
in the clouds surrounding the peaks. Bands of clouds appearing to
have a cellular structure extend north from the canyon, and the areas
within and immediately surrounding the chasm exhibit water-ice fogs.
[211-5049; 5°S, 105°W]"
"Early Morning Surface Fog. The presence of morning fogs in some
crater and channel bottoms is a Viking discovery with possible
implications for the future biological exploration of Mars. These
early morning views of the Memnonia region were taken one-half hour
apart using a violet filter to enhance the contrast of the
condensates. The areas marked by arrows are noticeably brighter in
the later picture. The fogs indicate specific spots where water is
exchanged, probably on a daily cycle, between the surface and the
atmosphere. The surface and lower air layers in this region become
unusually cold at night because of the thermal properties of the
surface. When the surface warms in the morning, it seems that a small
amount of water vapor-estimated to be about one-millionth of a meter
thick if liquefied is driven off; this vapor recondenses in the
atmosphere, which warms more slowly, to form a ground fog of ice
particles. [P17487; 13°S,147° W]"
"Early Morning Clouds in Noctis Labyrinthus. Condensate clouds are
seen here in early morning in the canyons of Labyrinthus Noctis,
which lies at the western end of the equatorial Valles Marineris
system. This picture, which covers about 90 000 km2, was made by
combining three frames of the same field taken through violet, green,
and red filters. Although these clouds lie mainly down inside the
canyons, they evidently extend above the walls and spill over some of
the surrounding plateau. Like most condensate clouds in the Martian
troposphere, they are believed to be composed of water-ice crystals.
[P18114, 9°S, 95°W]"
http://history.nasa.gov/SP-441/ch12.htm

See also the large size images of Noctis on this page:

Clouds in Noctis Labyrinthis.
http://planetscapes.com/solar/cap/mars/noctis.htm

The GRS readings suggest these may indeed arise from water in the
soil. Since this is a low latitude and low altitude site, this water
may remain in liquid form for part of the day.

Clouds in Noctis Labyrinthus.

Bob Clark