The Mars exploration architecture proposed by NASA envisages the launch of a mission to Mars at every possible launch opportunity, that is, every 26 months. The missions considered for the period from 2007 to 2016 are as follows:1,2

  • 2007, Phoenix (the first competitively selected Mars Scout);

  • 2009, Mars Science Laboratory;

  • 2011, Mars Scout (the second competitive selection for flight);

  • 2013, Mars Science and Telecommunications Orbiter; and

  • 2016, Astrobiology Field Laboratory or two Mid Rovers or the Mars Long-Lived Lander Network.

Phoenix and the Mars Science Laboratory are both in phases C/D of their development. NASA selected two Mars Scout concepts for phase-A studies in early 2007. All the other missions listed above are in pre-phase-A concept-study development at the present time.

An additional mission likely to be flown in this same period is the European Space Agency’s ExoMars rover, which is currently scheduled for launch during the 2013 launch opportunity.


The Phoenix mission, scheduled for launch in August 2007, is the first of NASA’s principal-investigator-led, competitively selected Mars Scout missions. The importance of the Scout program to Mars exploration rests in its ability to address high-priority science goals related to unexpected discoveries and in the opportunity they provide for maintaining program balance. These factors led the solar and space exploration (SSE) decadal survey to rank the Mars Scout program as the highest-priority activity in the small Mars mission category.3

When Phoenix lands on Mars in May 2008, it will begin a program of investigations specifically designed to measure volatiles (especially water) and complex organic molecules in the arctic plains of Mars, where the Mars Odyssey orbiter has discovered evidence suggesting ice-rich soil very near the surface. The science objectives of Phoenix are as follows:

  • Understand the water cycle and its interactions with the atmosphere and the regolith;

  • Determine the recent history of water and its role in shaping the surface; and

  • Assess whether or not the landing site is a habitable zone by looking for organics and other biogenic elements.

These objectives will be addressed via an instrument package which includes the following: a stereoscopic imager (SSI) and a descent imager (MARDI); a thermal- and evolved-gas analyzer (TEGA); a microscopy, electro-chemistry, and conductivity analyzer (MECA); and a meteorological station (MET). Samples to be analyzed by TEGA and MECA will be collected with the assistance of a camera-equipped robotic arm.

Mars Science Laboratory

The Mars Science Laboratory is an advanced rover mission designed to follow the highly successful Mars Exploration Rovers, Spirit and Opportunity. The primary goal of the mission is to assess Mars’s potential as a past or present abode of life, that is, to determine whether Mars ever was, or is still today, an environment able to support microbial life. The specific scientific objectives are as follows:

  • Determine the nature and inventory of organic carbon compounds;

  • Inventory the chemical building blocks of life (i.e., carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur);

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