Two rovers to the same site on Mars, 2018: possibilities for cooperative science.

Within the framework of the proposed joint NASA/ ESA 2018 mission to Mars, the 2-Rover International Science Analysis Group (2R-iSAG) committee was convened by the Mars Exploration Program Analysis Group (MEPAG) to evaluate the potential for incremental science return through the simultaneous operation at the same landing site of two rovers, specifically, ESA’s ExoMars and a NASA-sourced rover concept designated here as MAX-C (Mars Astrobiology Explorer-Cacher). The group was asked to consider collaborative science opportunities from two perspectives: (1) no change to either rover and (2) some change allowed. As presently planned and envisioned, the ExoMars and MAX-C rovers would have complementary scientific objectives and payloads. Initiated in 2002 and currently approved for launch in 2018, ESA’s ExoMars has the following scientific objectives: (1) to search for signs of past and present life and (2) to characterize the subsurface in terms of its physical structure, the presence of water/ice, and its geochemistry. The payload selected to achieve these goals is centered on the ability to obtain samples from the subsurface with a 2 m drill. The payload comprises panoramic and high-resolution cameras and a close-up imager (microscope) as well as a ground-penetrating radar to characterize the surface and subsurface environment and to choose relevant sites for drilling. Infrared spectroscopy would provide downhole mineralogy, while the mineralogy of the drilled materials would be obtained by IR/Raman spectroscopy and X-ray diffraction. Laser desorption–gas chromatography–mass spectrometry and pyrolysis gas chromatography–mass spectrometry would determine the composition of organic molecules, including any chiral preference in molecular structure. A life marker chip is designed to detect and identify markers of fossil or extant life. The currently proposed objectives of MAX-C are to cache suitable samples from well-characterized sites that might contain evidence of past life and prebiotic chemistry in preparation for a possible future Mars Sample Return (MSR) mission. The emphasis is on detailed site evaluation to determine the potential for past habitability and preservation of physical and chemical biosignatures. The strawman payload (which has not been selected) is therefore likely to include instrumentation for surface characterization, for example: an abrading tool; a 5 cm drill; a panoramic camera and near-IR spectrometer; a set of armmounted instruments capable of interrogating the abraded surfaces by creating co-registered 2-D maps of visual texture, major element geochemistry, mineralogy, and organic geochemistry; and a rock core acquisition, encapsulation, and caching system. The value of collaborative activity can only be judged with respect to a stated scientific objective. To this end, the previously stated objectives of ExoMars and MAX-C as independent entities have been analyzed for significant common aspects. We conclude that these two rovers have two crucial shared objectives that could, in fact, form the basis of highly significant collaborative exploration activity. We therefore propose the following set of shared scientific objectives for a 2018 dual rover mission that consists of both a shared component and an independent component.