Digging deep for ice in Isidis Planitia—New constraints on subsurface volatile concentrations from thermal modeling

The Isidis Planitia region on Mars usually is regarded as a comparably attractive site for landing missions based on engineering constraints such as elevation and smooth regional topography. The Mars Express landed element Beagle 2 was deployed to this area, and the southern margin of the basin was selected as one of the backup landing sites for the NASA Mars Exploration Rovers.Especially in the context of the Beagle 2 mission, Isidis Planitia has been discussed as a place which might have experienced a volatile-rich history with associated potential for biological activity e.g. Bridges et al., 2003. Selection of the landing site in Isidis Planitia of Mars Probe Beagle 2. J. Geophys. Res. 108(E1), 5001, doi: 10.1029/2001JE001820]. However the measurements of by the GRS instrument on Mars Odyssey indicate a maximum inferred water abundance of only 3 wt% in the upper few meters of the surface Feldman et al., 2004. Global distribution of near-surface hydrogen on Mars. J. Geophys. Res. 109, E09006, doi: 10.1029/2003JE002160]. Based on these measurements this area seems to be one of the driest spots in the equatorial region of Mars.To support future landing site selections we took a more detailed look at the minimum burial depth of stable ice deposits in this area, focusing as an example on the planned Beagle 2 landing site. We are especially interested in the likelihood of ground ice deposits within the range of proposed subsurface sampling tools as drills or ‘mole’-like devices Richter et al., 2002. Development and testing of subsurface sampling devices for the Beagle 2 Lander. Planet. Space Sci. 50, 903-913] given reasonable physical constraints for the surface and near surface material.For a mission like ExoMars Kminek, G., Vago, J.L., 2005. The Aurora Exploration Program—The ExoMars Mission. In: Proceedings of the 35th Lunar and Planetary Science Conference, abstract no. 1111, 15-19 March 2004, League City, TX] with a focus on finding traces of fossil life the area might be of potential interest, because these traces would be better conserved in the dry soil. Modeling and measurement indicate that Isidis Planitia is indeed a dry place and any hypothetical ground ice deposits in this region are out of range of currently proposed sampling devices.