Southern Utah 'marbles' may offer clues to Mars

When Marjorie A. Chan saw the first photographs of little nodules on the Red Planet, she thought, "Oh, my gosh, there's been groundwater flow on Mars."

Sitting in her office in the University of Utah's William Browning Building, she cupped a double handful of small iron spheres called Moqui marbles. The "marbles" came from southern Utah — but they looked so much like the nodules in the Mars rover photos that they almost could have been collected on the desolate plains of Meridiani Planum.

Moqui marbles and the Mars nodules are similar because they probably came about in much the same way, according to research by Chan and colleagues. And since they know how the Utah concretions formed, that is a strong tip-off about how those of Mars originated.

Most likely, it means Mars also hosted liquid water at one time in its long history. That fact could be crucial to the search for life elsewhere in the solar system, as life as we know it depends on water.

Chan, a professor and the chairwoman of the U. Department of Geology and Geophysics, is the lead author of an article just published in Nature Magazine, "A possible terrestrial analogue for hematite concretions on Mars."

In addition, the Utah spheres might point to a good place to search for Martian fossils, she believes. Moqui marbles probably precipitated more quickly because of the presence of bacteria in the porous Navajo sandstone. If a future Mars sampler probe collects nodules and returns them to Earth, they might include microscopic fossils.

Hematite is a form of iron, and the Moqui marbles are largely iron, sometimes with sand remaining in the center.

Rover scientists call the Martian nodules "blueberries" because they are slightly grayer than the orange rock and sand of that region on Mars. When the team used the rover's spectrometer to analyze a group of blueberries, they discovered they were made of hematite, an iron ore.

"Hematite is one of the few minerals on Mars that are directly linked to water processes," Chan said.

For about eight years, she has been looking for the reason that southern Utah sandstones are of different colors, and trying to understand how the colors relate to Moqui marbles found there. Many of Utah's iron spheres, which can range from tiny to several inches across, are from areas where the sandstone is white.

"We realized that a lot of these concretions formed from the interactions of different kinds of water," she said.