Geochemical Analysis of Soils from Extreme Environments on Earth and Mars.
Abstract: Geochemical analysis of soils, including the determination of pH,
salinity and organic content can provide insight into the environmental history and
habitability of the region from which they are collected. This dissertation focuses on the
geochemical analysis of soils from three extreme environments: the North Polar Region of
Mars, the McMurdo Dry Valleys (MDV) of Antarctica, and ... read morethe Atacama Desert in Chile. Also
included is a novel instrument for the electrochemical analysis of Martian soils for total
organic carbon. The Wet Chemistry Laboratory (WCL) aboard the 2007 Phoenix Mars Scout
Lander performed the first aqueous analysis of the Martian soil. WCL found a slightly
alkaline soil dominated by soluble sulfate, perchlorate, magnesium and sodium with
contributions of soluble potassium, calcium and chloride. The discovery of perchlorate on
Mars suggests the presence of oxidizing chemistry in either the atmosphere or soil. The MDV
and the Atacama are good terrestrial analogs for Mars, with all three environments
possessing similarities in climate and topography. Soil samples from the Atacama Desert and
MDV were analyzed to determine their chemical properties. Soils in both environments
exhibit similar ionic species and pH. Most interestingly, perchlorate was found at the
microgram per kilogram level in all soils from the MDV stable upland microclimate zone.
This helps strengthen the argument that perchlorate is ubiquitous on Earth and accumulates
only in hyperarid regions. The chemical properties of the soils from both of these extreme
environments were compared to the properties of the Martian soil as determined by WCL.
Neither environment's soil was drastically different from Mars. However, the soils from the
stable upland climate zone in the MDV were found be the better terrestrial analog for the
Martian soil at the Phoenix Lander site. One vital piece of information about the soil
composition on Mars has yet to be discovered, the amount of organic material present. The
Mars Organic Carbon Analyzer (MOCA) is an alternative approach to determine Martian soil
organic content. A prototype instrument has been developed and initial tests of its
viability are described.
Thesis (Ph.D.)--Tufts University, 2011.
Submitted to the Dept. of Chemistry.
Advisor: Samuel Kounaves.
Committee: Jonathan Kenny, David Marchant, and Arthur Utz.
Keywords: Chemistry, Analytical chemistry, and Geochemistry.read less