ROVER INSTRUMENTATION: IDENTIFYING EXTRATERRESTRIAL BIOSIGNATURES

Of the telluric planets in our solar system, Mars is the most likely to preserve evidence of life. Although Mars has a thin atmosphere today, its early history may have been habitable. The three rovers sent to Mars share a common mission, to explore whether or not Mars has or ever had a habitable surface environment. To date, these rover missions have identified several ancient environments that were potentially habitable, including: fluvial, lacustrine, and subsurface water systems.

Like their terrestrial counterparts, habitable environments on Mars have a range of potential for biosignature preservation. At a scale detectable by rovers, water-influenced sediments may preserve evidence of biological activity, including microbially-induced sedimentary structures (MISS) in clastic rocks and microbialites in chemical sedimentary rocks. Identifying these mesoscale structures and confirming whether they are microbially influenced is a challenge due to the size and subtle nature of their features.

Differentiating abiotic sedimentary structures from MISS and microbialites is a challenge even for geologists on Earth. It is even more difficult to distinguish these features for operators of a rover millions of km away. Choosing instruments that are capable of capturing the scale and detail of these features is crucial to finding biosignatures on Mars. If the wrong resolution is used, or the feature observed is too far away to capture the detail, the biosignatures will be overlooked and the mission will be unsuccessful.

Research with the Geo-Heuristic Operational Strategies Test (GHOST) team has tested various methods of traverse and collection strategy. These field tests compared efficiency and effectiveness of differing methods to locate, identify, and collect biosignatures. The field work conducted in the spring of 2016 demonstrated that mesoscale (0.1-10 mm) data is crucial when identifying MISS and microbialites. Without clear resolution on the sub-mm to cm scale, key features that allow confident assessment of biogenicity are unrecognizable. Further research is being conducted on the type of instrumentation necessary for identifying mesoscale biosignatures, specifically what resolution will be needed for distinguishing MISS and microbialites from abiogenic structures at outcrop scale.