• Identify features that may represent the effects of biological processes;

  • Investigate the chemical, isotopic, and mineralogical composition of the martian surface and near-surface geological materials;

  • Interpret the processes that have formed and modified rocks and regolith;

  • Assess long-timescale (i.e., 4-billion-year) atmospheric evolution processes;

  • Determine the present state, distribution, and cycling of water and carbon dioxide; and

  • Characterize the broad spectrum of surface radiation, including galactic cosmic radiation, solar proton events, and secondary neutrons.

These goals will be addressed by a comprehensive suite of experiments including a panoramic mast camera (MastCam), a microscopic imager (MAHLI), and a descent imager (MARDI); an alpha particle x-ray spectrometer (APXS), a laser-induced-breakdown spectrometer and microimaging camera (ChemCam), a gas chromatograph-mass spectrometer and tunable laser spectrometer system (SAM), and an x-ray diffraction/x-ray fluorescence instrument (CheMin); an environmental radiation monitor (RAD) and a neutron spectrometer (DAN); and a meteorological package (REMS).

Although the MSL mission was not well defined at the time the SSE decadal survey was drafted, its importance to addressing key Mars science goals was recognized and this mission was determined to be the highest-priority medium-cost Mars mission for the decade 2003-2013. Since then the scope and cost of the mission have grown significantly.

The combination of MSL’s highly capable science payload, its long expected lifetime, and its use of as-yet-untested entry, descent, and landing systems have led some observers to suggest that it would be prudent to send two. Indeed, NASA’s 2005 Roadmap for the Robotic and Human Exploration of Mars recommends that two MSL spacecraft should be launched “to ensure mission success and maximize the science return.”4 Such an approach might be an appropriate risk-reduction strategy. However, its implementation at such a late stage in the development of a large and complex mission seemed ill advised, irrespective of its financial implications for the rest of the Mars program.5

Mars Scout 2011

NASA proposes to launch the second Mars Scout missions no later than January 2012. NASA released an announcement of opportunity for this mission in early May 2006 and, 9 months later, selected two candidates for additional studies, the Mars Atmosphere and Volatile Evolution mission (MAVEN) and The Great Escape. Given the competitive nature of the Scout program, the detailed scientific goals and capabilities of these two orbiters remain proprietary. Nevertheless, it is understood that both spacecraft are designed to address questions relating to the composition and evolution of the martian atmosphere, in general, and the structure and dynamics of the upper atmosphere and ionosphere, in particular. As such it is likely that both MAVEN and The Great Escape are responsive to the scientific goals of the Mars Upper Atmosphere Orbiter, a high-priority mission identified in the SSE decadal survey report.6 NASA plans to select one of these two candidates for flight implementation in January 2008. In addition to selecting these two spacecraft missions, the Mars Scout program is also funding three U.S. teams providing scientific and/or instrumental contributions to the ESA’s ExoMars rover mission.

Mars Science and Telecommunications Orbiter

The Mars Science and Telecommunications Orbiter (MSTO) is envisaged as being comparable in size, scope, and cost with the Mars Reconnaissance Orbiter and capable of addressing a broad range of scientific objectives associated with the study of Mars’s atmosphere and space-plasma environment. Its scientific goals and instrument complement are only partially defined at the moment. Science goals endorsed in the recently completed study by MEPAG’s Mars Science and Telecommunications Orbiter Science Analysis Group include the following:7

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