This Master of Science diploma project in Space Engineering was performed
at NASA Ames Research Center and is based on images from the Mars Orbiter
Camera. Pictures taken by this camera onboard the Mars Global Surveyor show
gully features resembling water-carved gullies on Earth. One theory of
gully formation on Mars contends that the source of the water feeding the
gullies is a shallow liquid water aquifer. Interestingly, the gullies tend
to form in locations of relatively low ice content. The shallow aquifer
theory was quantitatively tested by calculating the temperature and
pressure of the Martian subsurface at the measured alcove base depths in
order to determine if liquid water can exist at these locations.
Since the density and thermal conductivity of the soil depend on the amount
of ice in the soil, the ice-to-soil ratio is an important factor. The
thermal conductivity and density of the soil were calculated for the
location of the gullies, assuming that the ice content in the soil would be
the same at all depths down to the alcove base depth.
Around 59% of the gullies were found to fall outside of the temperature and
pressure regime of liquid water at the alcove base depth when assuming an
overburden consistent with the observed GRS ice content. However, it may be
unrealistic to assume that the measured GRS ice content extends down to the
depth of the gully alcoves. Therefore the thickness of a dry layer that
must exist within the overburden column for the water to be liquid at the
alcove base depth is estimated. These calculations build on the assumption
that the soil has a fraction of overburden with dry and icy components
where the icy layer has the same concentration of ice as measured by GRS.
According to these calculations, liquid water could exist in approximately
81% of the gully locations.
Some 19% of the gully locations could not have liquid water at the depth of
the alcove base because the required thickness of the dry layer exceeds the
alcove base depth. For the gullies where liquid water cannot exist under
the surface, no outstanding characteristics were found regarding the
albedo, elevation, channel length and thermal inertia. However, all of
these gull...
