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Crater Provides Knowledge of Ancient Martian Environment

A crater on Mars’ surface provides scientists with an idea of the ancient Martian environment. The objective of NASA’s Curiosity rover mission is to explore and analyze possible signs of past or present life on Mars’ surface. The rover spent three-and-a-half years investigating and taking samples from the Gale Crater—a lake once fed by rivers and groundwater—to determine chemical conditions.

The former lake existed more than three billion years ago; however, more recent research determined that the lake was also stratified, or separated, into layers. Stratified bodies of water demonstrate distinct differences in chemical or physical properties in each layer. For the Gale Crater, oxidizing agents existed in substantial amounts near the surface whereas reducing agents resided in deeper layers. Such redox stratification caused variations of environments in different layers.

“These were very different, co-existing environments in the same lake,” stated lead author Joel Hurowitz of Stony Brook University. “This type of oxidant stratification is a common feature of lakes on Earth, and now we’ve found it on Mars. The diversity of environments in this Martian lake would have provided multiple opportunities for different types of microbes to survive.”

To analyze the chemical environment of the Gale Crater, the researchers examined fine-grained sedimentary rocks which provided clues to ancient Martian processes. These rocks were investigated using geochemical and mineralogical analysis techniques, along with high-resolution color imagery. Two mudstone units were considered; one from the base of the stratigraphic section and another from a higher position of the stratigraphic section. Distinct property differences in the two mudstone units existed due to fractionation of detritus in shallow water and redox stratification of lake water body, causing oxidizing conditions in shallow water.

Scientists are currently using data collected by ChemCam—a device on Curiosity designed to provide elemental compositions of rocks and soil—and other instruments to get a better understanding of the Martian past. Previous discoveries of organic carbon compounds, nitrogen, and other minerals suggest that Mars possessed a habitable environment around approximately 3.8 billion to 3.1 billion years ago.

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Editor: Ramneet Chauhan