Martian Rocks Shaped by Acidic Waters

The NASA MER Opportunity has been roving on the surface of the Red Planet for more than six years. During this time, it surveyed numerous areas of the Meridiani Planum extensively, especially in the region around its landing site. The instruments and cameras on the robotic explorer managed to collect a wealth of scientific data, which now seems to point at a very interesting conclusion. Experts say that some of the rocks in the area may have formed and take shape under the action of acidic waters.

Investigators based their conclusions on careful analysis of the dry rock outcrops surrounding Meridiani Planum. They say that the entire location may have been completely submerged under water more than a billion years ago. Extensive analysis of the data Opportunity sent back on the rocks it came across appears to indicate a possible mechanism through which the water became acidic. Researchers at the NASA Jet Propulsion Laboratory (JPL), who manage the MER mission, say that the acidity may have been caused by iron-rich groundwater.

The liquid may have risen to the surface, and then suffered a number of chemical reactions, that eventually changed the type of iron it contained, and boosted the acidity of the waters above. The rocks which Opportunity observed for the research are estimated to be more than 3.7 billion years old, which means that they formed less than a billion years after Mars itself did. A closer analysis of the stones revealed that they exhibited patterns similar to counterparts on Earth that formed in arid regions, but under conditions of periodic groundwater upwelling. Particular minerals found in the rocks hint at the high acidity of the waters that flowed over.

A team of JPL experts is currently investigating “whether or not you're able to pick up enough iron along those groundwater flow paths and bring them to the surface and have all this acid chemistry take place,” says Joel Hurowitz, a member of the team managing Opportunity. At this point, it is estimated that the waters had a pH level of between 2 and 4, he told Space in an interview. Details of the new investigation were published in the April 4 online early issue of the esteemed scientific publication Nature Geoscience.