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Mars 'blueberries' give strong support to water theory

The tiny, round "blueberries" found on Mars by Opportunity rover strongly support the theory that water once existed on the Red Planet, a NASA scientist has said.


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Blueberries On Mars
The tiny, round "blueberries" found on Mars by Opportunity rover strongly support the theory that water once existed on the Red Planet, a NASA scientist has said.

Philip Christensen, a scientist from NASA's Jet Propulsion Laboratory in Pasadena, California, announced the finding at the 35th annual Lunar and Planetary Science Conference being held this week in Houston, Texas.

At Meridiani Planum where Opportunity has landed, a patch of tiny spherules -- also called "blueberries," was closely examined by a German-made Spectrometer at the rover's robot arm, and has now been identified as hematite, which is typically formed in water. The spectrometer is designed to study minerals that contain iron, which are common on the Martian surface.

"I'm becoming more convinced, from the evidence, that there's been a standing body of water on Mars," said Philip Christensen, principal investigator for the miniature thermal emission spectrometer aboard Opportunity. "It probably extends the lifetime of water at this site."

Christensen told Space.com that the formation of hematite concretions isn't a geological process that happens rapidly, such as crystals that can grow in weeks or months.

"It's a process that measured in years and decades, not weeks or weekends," he said, adding that on Earth such objects have taken thousands of years to form. "I don't know if it's that long on Mars or not," he cautioned.

"I think, for now, the surface water story and the groundwater story are two different ones which may have a common happy ending," Andrew Knoll, a science team member with the Mars Exploration Rover mission, said during a press conference Thursday. But the hematite in the Martian blueberries, he added, "really speaks to groundwater very specifically."

The sedimentary rock containing the hematite-bearing spherules also contains other minerals that not only had to be placed by water, but most likely by groundwater, he added.

Knoll, however, said that standing water was not a prerequisite for the hematite finding, citing that similar processes have taken place here on Earth, such as in Utah, where sandstone outcrops were gradually saturated by groundwater as the water table rose over time.

Earlier this month, Opportunity has uncovered geologic evidence that the flat, featureless Meridiani Planum once was covered with water. Three days later, scientists announced that Opportunity's twin, Spirit, discovered signs that small amounts of water once welled up in the soil of Gusev Crater where the rover landed on Jan. 3.

The composition of the blueberries was a mystery when they were first detected because the spherules were too small - just a tenth of an inch (3 millimeters) in diameter - to target with the Opportunity's instruments.

Earlier this month, scientists surmised they were concretions of material dissolved in the water that soaked through the rocks of an outcrop near the rover. Over time that material built up into the round, gray objects dubbed blueberries, some of which remained embedded in the rock while others weathered out and onto the Martian floor.

Opportunity ultimately examined a group of blueberries that had weathered out of its sedimentary prison and collected in an area called the "Berry Bowl." The grouping allowed the rover a large enough sample area to use its iron-sniffing M?ssbauer spectrometer, as well as its miniature thermal emission and alpha particle X-ray spectrometers.

By studying a berry-rich area in the "Berry Bowl" as a whole, then a berry-free patch nearby, scientists were able to filter out sedimentary material until they were left with a strong hematite reading from the "blueberries."

More to learn
Hematite is a mineral that typically, though not always, forms in water. Orbital studies of the Meridiani Planum site indicated large tracts of the mineral across the region, which led mission planners to select the area for Opportunity's visit. The region itself is about the size of Oklahoma, and mission scientists are eager to see if "blueberries" there suggest the same kind of weathering on the plains as seen at Opportunity's outcrop, which sits inside a small crater.

"If you look at this outcrop, it's about 30 centimeters [12 inches] of sediment that contains maybe 2 to 3 percent of hematite," Knoll said. "Perhaps the whole floor of Meridiani Planum is covered with them, and if that's true, then a much larger volume of rock was stripped away by erosion through time."

Knoll, Christensen and other mission scientists are anxious to unleash Opportunity onto the Meridiani plains to search for more spherules, hematite and evidence of past water on Mars.

"I think there's a decent chance that we'll find more spherules outside the crater," Cornell University's Steven Squyres, principal investigator from the rover missions, said in an e-mail interview. "We clearly see spherules in the soil of the crater wall above the outcrop, and unless they can be blown uphill, that means they rolled down from above."

Source: agencies


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