Rover cracks mystery of Mars spheres
By Leonard David
(SPACE.com) -- Scientists have learned the composition of the mysterious sphere-shaped objects scattered across the crater floor at Meridiani Planum, the landing site of the Opportunity Mars rover.
By using a Mössbauer Spectrometer mounted on Opportunity's robot arm, a patch of the tiny spherules -- also called "blueberries," although they are not blue -- received close examination and have now been identified as hematite.
The spectrometer is designed to study minerals that contain iron, which are common on the martian surface. Also used to pin down the makeup of the spherules was the rover's Mini-Thermal Emission Spectrometer, a scientific instrument that can recognize minerals formed in water.
Meridiani: shallow lake?
This new evidence further supports the hypothesis that the hematite mineral was likely formed in a former standing body of water. The Meridiani area, it is thought, was once a shallow lake.
Once Opportunity wheels itself out of its current shallow crater site, scientists expect the hematite-rich spherules to litter the landscape at Meridiani Planum.
Philip Christensen, a Mars Exploration Rover scientist from Arizona State University in Tempe, announced the finding this week at the 35th annual Lunar and Planetary Science Conference being held in Houston, Texas.
Formation via precipitation
"This finding further supports the hypothesis that these interesting 'Mars balls' are actually sedimentary concretions, rather than any of the other working hypotheses," said James Garvin, lead scientist for Mars Exploration and the Moon at NASA Headquarters in Washington, D.C.
There have been a variety of contending theories for what may have caused the unusual mineralogy at Meridiani, including volcanic causes.
Garvin said that this latest finding strongly supports the view that the rocks in the outcrop at Meridiani have been modified by water -- a determination made already through other research at the site.
"Hematite as a major compositional phase in the spherules supports their formation via precipitation, rather than as impact-related fallout," Garvin said.
"So, the story is getting better... and multiple lines of independent evidence support water-related chemical 'processing' of the rocks," Garvin added. "Now all we have to do is figure out what made the rocks in the first place and how long the water may have been involved in the 'soakings.' What a fun time!"
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