surface missions depend upon the landing site selected and the completeness of the available geological, climatological, and geophysical context…. A network of landers, carrying seismic sensors, heat flow probes and the capability for making high-precision geodetic measurements, is needed to better understand the structure, state and processes of the martian interior in order to ascertain thermal and geological evolution of the planet that is responsible for the surface we see today.”¹

In view of the importance of Question 3, and the current imbalance in the proposed architecture, the committee reiterates the recommendation already made to include a geophysical/meteorological network mission as a third possibility for the 2016 launch opportunity. It could be argued that the inclusion of this mission will require significant new technology investments at a time when only limited funding is available. The committee does not think this is the case. The concept of a Mars network was studied extensively by NASA in the early 1990s as part of the Mars Environmental Survey (MESUR) project.² A prototype of the MESUR landers—MESUR Pathfinder, later renamed Mars Pathfinder—was successfully flown and operated on Mars in 1997. Additional development work has been undertaken in the context of the Pascal Mars Climate Network mission, which has been proposed as a Discovery and a Mars Scout mission.³ Finally, additional developmental activities have been undertaken in Europe in the context of a variety of concepts, including MARSNET, INTERMARSNET, and, most recently, NETLANDER.⁴

Although the committee has not seen detailed cost studies and is not appropriately constituted to undertake such studies itself, it is of the opinion that the cost of an adequate network mission is comparable with that of the