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Accomplishments to date and next steps
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Highest priority: establishing that life is or was present on Mars, or, if life never was present, understanding why not; distribution and history of water; sources of biologically usable energy; composition, states, and reservoirs of C, N, S, O, H, and P
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Climate change as a central theme; history and process; emphasis on process
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None identified in reporta
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None identified in reporta
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Improved knowledge to date
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Liquid water has been present and weathered the crust; crust complex and diverse with early sustained hydrological cycle, episodic volcanic eruptions, and climate cycles driven by obliquity; putative observation of methane
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Primary progress has been from the Thermal Emission Spectrometer, the Mars Orbiter Camera, and the radio science from Mars Global Surveyor; seasonal cycles of dust, temperature, and water discerned; boundary layer observations are not complete; upper atmosphere only sparsely sampled; vertical mixing and trace gas loss rates not yet examined
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Geological evolution of planet from previous missions and current MER rovers; geological diversity and complex evolution; dynamo early in planet’s history and volcanic emissions may have helped provide active hydrothermal systems; previous beds under salty groundwater identified; chemistry bounds deduced on hydrological cycle on surface; possible relation to long-term orbital obliquity changes
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Risks to humans can be mitigated through precursor scientific investigations (~20 identified), with four having high priority: water accessibility near landing site, wind shear and turbulence effects on landing, martian life effects on Earth’s biosphere, and adverse effects of dust on mission hardware; also level of radiation exposure, but technical development and flight systems on hold due to fiscal constraints
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Potential outcomes of near-term investigations
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May find water and/or ice reservoirs; may discover more biologically significant landing sites
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Most promise from MRO observations, lower atmosphere in greater detail; landed spacecraft will likely not constrain boundary-layer processes; surface- atmosphere aerosol fluxes will remain beyond observation; high latitudes of unique importance
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MRO to provide identification of sites with mineralogical evidence of habitability, and ground-penetrating radar may find evidence of groundwater and subsurface ice; Phoenix to characterize chemistry, mineralogy, and isotopic composition of evolved gases in subsurface soils and ices; MSL to provide detailed exploration of potential habitable site identified from orbit
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Phoenix for evaluation of accessibility of water at high latitudes; MRO for maps of atmospheric properties; need both long-and short-term atmospheric state and variability; MSL for effects of dust on landed systems; landed mass increase from 0.2 to 1.5 metric tons; MSL for addressing human health
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