The current version of the model has been developed over the last years in this group, funded by the German Research Council (DFG). While the developement of such a model is always ongoing, it has already been used sucessfully to study different landing sites on Mars. For the Beagle 2 landing site in Isidis Planitia we have studied the subsurface temperature distribution and have derived a map for the minimal burial depth of ground ice deposits. For the MER backup landing site in Isidis Planitia we have performed studies on the stability of ice for different subsurface structures. For Gusev Crater and for Terra Arabia we are currently studying scenarios for shallow longtime stable ice deposits. For the NASA Phoenix mission we have just start working on assessing the landing site candidates.
As part of the analysis of data from the Planetary Fourier Spectrometer (PFS) on Mars Express (PI: V. Formisano, IFSI) the BMST is used to model surface temperatures. In combination with the measured data this can be used to derive the thermal inertia of the surface material. One of the most exciting ideas about combining BMST with PFS measurements is the search for active hot spots on Mars. Should such a hot spot exist today it would be the most likely place to find biological activity.Most models used to study the thermal behavior of the near surface layer on Mars assume constant physical properties with depth. The BMST is based on a layered structure of the subsurface material, in which each layer can have different physical and thermo-physical properties. Based on the observation of layered terrain as reported for example by the Mars Exploration Rovers this is a more realistic approach.
The main features of the BMST are a high vertical resolution down to the centimeter range, the realistic treatment of the thermal properties of ice-rock mixtures, a detailed treatment of gas flux within the surface and into the atmosphere and a variable temporal resolution which allows to study daily as well as annual variations.
The simplified sketch shown on the right gives an idea of the working principle of the BMST, our so called ?Dirty ice approach?. We start the modeling assuming a porous layered soil in which the pores are filled to a certain percentage with ice (mainly H2O and or CO2). During the simulation we calculated the thermal behavior, the energy transport and the gas flux within the soil during the Martian orbits. The simulation continues until the model has reached a steady state. This end condition gives an estimate on the minimal burial depth at which ice would be stable over annual cycles. Typically steady state is reached after 1000 or more Mars orbits.
The BMST is highly comlementary to measurements performed by the Gamma Ray Spectrometer (GRS) instrument on Mars Odyssey. This is the first instrument providing direct measurements of the water abundance within the first 2m of the Martian soil. However the spatial resolution of the GRS data is extremely coarse with a footprint of about 600km. To increasing the probability of finding near surface ice deposits at landing sites an extensive modeling effort is necessary.