Geologist's Report
Date: April 21, 2015
Crew Geologist's Name: Auriane Canesse
Hello Earth,
Here is a summary of everything that has been done for our geology
experiment. I will begin by reminding briefly the goal of our study
and I will then describe the results we obtained.
\\introduction
The initial goal of our experiment was to map the magnetic
susceptibility of the ground in order to study its variation. The
susceptibility varies with the composition of the soil: it is quite
low for sand but very high for iron for example. But since our
instrument also measures electric conductivity, we decided to measure
this second property too.
\\ field sessions
We began by mapping the magnetic susceptibility of the ground around
the station then went to further places to take more measurements.
On April the 15th we mapped the surrounding of the hab but since
Gaspard's GPS didn't work we had to take positions by hand with a
meter. Since it was much slower than planed we took only two small
sets of measurements. For the first one we mapped an area of 25x3m
behind the hab. The buried tank behind the hab appeared very well on
the data. For the second set of measurements we took measurements
every 3m on 140m to see if there was a global change. But we only had
only insignificant variations around a constant mean. The magnetic
susceptibility of the ground seems quite uniform. We will try to take
new measurements at a totally new location to see if we measure
different values.
On April the 16th as we went to a dry river bed to take hydraulic
measurements we also took magnetic susceptibility measurements in the
river bed and on the banks but the results appeared to be similar to
the previous ones.
On the April 17th we took measurements on several hills close to the
station. Again, there was no significant changes of the magnetic
susceptibility.
On the April 18th we went to another river bed, the instrument was
showing biased results for the magnetic susceptibility because of the
heat. So we measured the electric conductivity of several river's
sections instead. We found interesting variations: it had rained on
the previous day and the conductivity appeared to be much higher in
the bottom of the river than on the banks (so its humidity was
higher). The two banks also had different mean conductivity values
which could explain the presence of plants on the right bank only (the
wetter one).
On the April 19th we went on the cliff West of the station to measure
susceptibility and conductivity. They both appeared to be
approximatively constant and not very different from the values
obtained in the plain.
On April the 21st, since the weather had been dry for 4 days we went
back to the second river to take more conductivity measurements in
order to compare them with the previous ones. We had expected the soil
to be dry but surprisingly it was still wet only 2cm below the clay
crust. The measurements we obtained were quite similar to the previous
ones: we measured the same river profile, which did seem coherent.
\\ Results
I will now sum up the results mentioned above
The magnetic susceptibility turned out to be uniform: the measurements
can be taken at different locations, on different geological stratum
(plain, hills, cliffs), with different humidity rates (stream-beds,
dry or rainy weather), the results are always similar: small
variations around a nearly null mean. The measured values don't seem
to be differentiable from the noise of the instrument.
The talkie-walkies interferes with the instrument (which is very
sensitive), therefore they should not be used while measuring. This
can be a problem for automatic measuring (instrument connected to a
computer) since the talkie-walkie's interference would not be
differentiable from soil abnormalities.
Magnetic susceptibility can be used to detect buried metallic objects,
like tanks (but I don't think we will loose any of these on Mars.)
The electric conductivity varies around river beds in a significant
way, it shows an important difference of humidity between the banks
and the bottom, even long after the last rain. The soil stays wet for
quite a long time (which isn't obvious for a desert).