Moqui Marbles and Martian Blueberries
The terms “Moqui marbles” and “Martian blueberries” may not seem very scientifically legitimate, but trust us, they are.
Moqui marbles are iron concretions that form in the iconic sandstones of southern Utah and Arizona. Groundwater percolating through the Navajo Sandstone in particular leaches iron out of the rocks, which eventually precipitates around sand grains. As iron continues to accrete to the metal-fringed grain, it grows larger and larger until a wonderfully spherical Moqui marble is formed.
A recent study has found that the age of minerals (goethite, hematite, and Mn-oxide) within Moqui marbles is significantly younger than the surrounding rock. The Jurassic Navajo sandstone is in the 190 ma ballpark, whereas Moqui marbles ranged from being 25 ma to as young as 300,000 years old!
What does this have to with Mars? Early in her lifetime, the trusty rover Opportunity discovered concretions commonly known as “Martian blueberries” … and they look suspiciously similar to Moqui marbles. If Moqui marbles on Earth form from groundwater flow, Martian blueberries could have serious implications for past environmental conditions on Mars. Did groundwater flow on Mars cause the blueberries to form? Are the blueberries also much younger than the rock, possibly indicating water that was more recent?
But wait, the plot thickens! Some scientists believe that bacteria also aid in the formation of Moqui marbles. These researchers suggest that the little black balls were originally siderite (an iron carbonate) and were morphed into hematite with the help of some microbial friends. Should that be the case, Martian blueberries could be signs of past life on Mars.
Certainly there is still a lot more to discover, but Moqui marbles and Martian blueberries may be some of the most interesting little rocks in the solar system.
-CM
For the original paper on the age of Moqui marbles:http://bit.ly/1BIUv9M
For the original paper on the possible organic origin of Moqui marbles: http://bit.ly/1KmG6Xb Photo credit: Luc De Leeuw http://bit.ly/1xSSv1t Photo credit: NASA