Landing site rationality scaling for subsurface sampling on Mars—Case study for ExoMars Rover-like missions

Subsurface sampling will be important in the robotic exploration of Mars in the future, and this activity requires a somewhat different approach in landing site selection than earlier, surface analysis focused missions. In this work theoretical argumentation for the selection of ideal sites is summarized, including various parameters that were defined as examples for the earlier four candidate landing sites of Mars Science Laboratory. The aim here was to compare interesting sites; the decision on the final site does not affect this work.Analyzing the theoretical background, to identify ideal locations for subsurface analysis, several factors could be identified by remote sensing, including the dust and dune coverage, the cap layer distribution as well as the location of probable important outcrops. Beyond the fact that image based information on the rock hardness on Mars is lacking, more work would be also useful to put the interesting sites into global context and to understand the role of secondary cratering in age estimation. More laboratory work would be also necessary to improve our knowledge on the extraction and preservation of organic materials under different conditions.Beyond the theoretical argumentation mentioned above, the size and accessibility of possible important shallow subsurface materials were analyzed at the four earlier candidate landing sites of Mars Science Laboratory. At the sample terrains, interesting but inaccessible, interesting and sideward accessible, and interesting and from above accessible outcrops were identified. Surveying these outcrop types at the sample terrains, the currently available datasets showed only 3–9% of exposed strata over the entire analyzed area is present at Eberswalde and Holden crater, and individual outcrops have an average diameter between 100 and 400 m there. For Gale crater and Mawrth Valles region, these parameters were 46–35% of exposed strata, with an average outcrop diameter of ∼300 m. In the case of the first two sites smaller and elongated outcrops were present in larger number, while in the second group average sizes of outcrops were around 3000 m in diameter. The analysis suggests that for future missions aimed at subsurface sampling, different exploration strategies would be ideal at different terrains, and the target terrain’s characteristics should be taken into account during the planning phase of the mission.

► Outcrops for subsurface sampling were categorized regarding their accessibility by rovers.
► At the four candidate landing sites of MSL differences were determined between the outcrops.
► Outcrops at Eberswalde and Holden sites were 100–400 m sized, elongated and close to each other.
► At Mawrth and Gale different size and distance of outcrops point to different exploration strategy.
► For subsurface sampling laboratory work is useful on rock strength and preservation potential.