Selecting Landing Sites on Mars

Dr. John Grant

Figure 1. Artist’s rendition of the Mars Science Laboratory rover on the floor of Gale crater.2

The Mars Science Laboratory (MSL) Curiosity mission is the next step in NASA's Mars Exploration Program following the Mars Exploration Rovers, Mars Reconnaissance Orbiter, and Phoenix missions. Launched in late 2011, the MSL rover arrived at Mars in early August 20121. The main objective of the MSL mission is to "assess habitability" of both Mars' past and present environments1. The Mars Landing site steering committee, co-chaired by Dr. John Grant, co-led  the science community MSL landing site selection process and helped evaluate the landing site in Gale crater where a thick mound of layered rocks (dubbed Mt Sharp) should yield information on the past conditions and habitability of Mars.

Curiosity is rich with technological advancements starting with the new innovative landing procedure and extending to the types of instruments loaded onto the very capable rover. The landing involved the descent of the spacecraft by parachute and immediately prior to landing, the lowering of the rover on a tether to the surface1. The MSL rover will be equipped to roll over obstacles up to 75 cm high. Through scooping and drilling the surface, the rover will be able to collect soil and rock samples that can be chemically analyzed in situ in test-chambers on the rover. To assess past habitability at the landing site, sample analyses will focus on identifying organic components, such as proteins and amino acids, and atmospheric gases essential for life. A few of the instruments incorporated into the rover structure include the Mast Camera, the ChemCam, the Sample Analysis at Mars Instrument Suite, Radiation Assessment Detector, and the Rover Environmental Monitoring program1.

The process to select the landing site for MSL was co-convened and co-chaired by Dr. Grant of CEPS and ended in 2011 after a series of four or five community workshops and exhaustive evaluation by the MSL Science Teams and Project at the Jet Propulsion Laboratory2. By involving the broad science community in these workshops, the process ensured identification of a landing site meeting all the specified engineering and safety requirements, as well as providing the greatest scientific value2. Landing site selection and evaluation activities relied heavily on data provided by the Mars Reconnaissance Orbiter (MRO) that enabled study of the four final candidate sites: Holden crater, Eberswalde crater, Mawrth Vallis, and Gale crater4.

A similar process was employed for selecting the landing sites for the Mars Exploration Rovers (MER) in Gusev crater and in Meridiani Planum5. The MER rovers landed on Mars in 2004 and the Opportunity rover continues its exploration of Meridiani Planum.

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1. NASA Jet propulsion Laboratory (2008).
2. Grant, J. A., et al. (2010), The science process for selecting the landing site for the 2011 Mars Science Laboratory, Planet. Space Sci., 59, 1114-1127, doi:10.1016/j.pss.2010.06.016.
3. Golombek, M. P., J. A. Grant, et al. (2012), Selection of the Mars Science Laboratory landing site, Space Science Reviews, doi:10.1007s11214-012SPAC875R1.
4. NASA Marsoweb (2008).
5. Grant, J. A., et al. (2004), Selecting landing sites for the 2003 Mars Exploration Rovers, Planet. Space Sci., 52, 11-21, doi: 10.1016/j.pss.2003.08.011.