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The Search for Source Rocks on Mars

Recent rover and orbiter missions to Mars show that sedimentary rocks are surprisingly common. Constrained to be billions of years old, these rocks are remarkably well preserved and represent diverse eolian, fluvial, deltaic, and evaporitic environments. Combined observations indicate that sufate-rich sedimentary rocks may be most abundant and are globally widespread over many hundreds of sq. km at low latitudes, forming thickness in excess of 2000 m. Facies observed by the Mars Exploration Rover Opportunity are dominated by porous eolian deposits with local fluvial reworking. Incipient evaporite playa facies, dominated by Ca and Mg sulfates, are also present.

The success of the MER mission stimulated development of an even more capable rover: Mars Science Laboratory (MSL), due to launch in 2009. The primary goal of MSL will be to directly assess the present and past habitability of Martian sedimentary rocks. MSL will include instruments capable of detecting organic compounds, measuring TOC, and determining the isotopic composition of biologically important elements such as C and S. Landing sites will be chosen that optimize the chance to encounter low energy sedimentary environments that maximize the accumulation of organic matter and preservation of potential biomarkers. Evaporites are strong candidates because of their known potential to preserve organic matter. A second important target would be clay-rich mudstones deposited in fluvio-deltaic or lacustrine settings. The detection of these environments must be based on orbital remote sensing, using spectroscopic data to detect preferred minerals, and image data to map depositional sequences and predict where fine grained rocks and evaporites are likely to occur.

Listen to 'Life on Earth and Mars' in our series of podcasts to hear John Grotzinger explain more about the mission’s aims, the technology on board, and what the future holds for Mars exploration.


John Grotzinger, Caltech


John Grotzinger is a geologist interested in the evolution of surficial environments on Earth and Mars. Field and subsurface exploration-scale mapping studies are the starting point for more topical laboratory-based studies involving geochemical, geologic, and geochronological techniques. He has a decade-long involvement with Petroleum Development Oman focused on production from intrasalt carbonate reservoirs. Currently, he is the Project Scientist for the Mars Science Laboratory Rover mission due to launch in 2011. He is also a member of the Mars Exploration Rover Science Team, and HiRISE camera imaging team on Mars Reconnaissance Orbiter. He is the Fletcher Jones Professor of Geological Sciences at Caltech.