Today Commander Gregory Leonard, Crew Engineer Victor Luo and Crew
Scientist Juho Vehviläinen did EVA number 3 to
study soil moisture on two sites. See more information about the sites
and the project in the first science report from 02 Dec
2014. Weather conditions: overcast and temperature around 10 degrees Celsius.
The weather has been stable in the vicinity of the MDRS in terms of
relative humidity and precipitation. Therefore, transects
from two days past (EVA1) were not repeated. Instead we concentrated
on the vertical distribution of soil moisture. On both
sites, named “Shrub” and “Barren” we did two profiles (=pits).
At the “Shrub” site the pits were dig on a small ridge and on flat
ground. As was expected, the point at the flat ground had
higher amount of water in the soil, since the water from the ridge has
presumably percolated downward on the slope. The
volumetric water content of soil ranged from almost zero to 13% at
depth of 30 cm.
At the “Barren” site one pit was done on dried up streambed and one on
a drier patch of soil that represents the “Barren” site
better as a whole. At the point of “dry patch of soil” the soil layer
on top of the bedrock was only 20 cm thick. At the “dried up
streambed” point the soil was packed so hard that in time allowed (20
mins) we were not able to get deeper. Inserting the soil
moisture probes’ rods was difficult at both of the points. This slows
down the measurements.
Generally rain and swift changes of weather are not desirable at the
MDRS. However, with this soil moisture study, changes in
weather would give us a better understanding of the dynamics of soil
moisture. After rain event we could do measurements at
the same locations to see how fast the water percolates into the
ground, and how much will stay there and in which layer. If
the weather stays the same, more measurements will give as better
understanding of the spatial distribution of the soil
moisture. This is equally important as the dynamics of soil moisture,
since it will tell us how many points we need to monitor in
the future to be able to characterize the soil moisture in a
designated area e.g. 500 meter or 2 km radius from the MDRS.