Iron ‘blueberries’ may be sign of microbial life on Mars

It’s unlikely anything lives on Mars today, but it may well have done so millions or billions of years past. And it may have left traces of its existence in the geology of the red planet.

One such tantalising hint was discovered by the NASA Opportunity Rover, which found small spherical hematite balls, dubbed ‘blueberries,’ in the Martian soil.

These were originally thought to have provided the first evidence of liquid water on Mars, but their existence may hold an even more profound implication.

Now researchers from the University of Western Australia and University of Nebraska have found that such iron-oxide spheroids, when they appear on Earth, are formed by microbes.

If the ‘blueberries’ found on Mars are of a similar composition, it could provide long sought strong evidence for the existence of life on the red planet.

One Earth, such spherical iron-oxide concretions are commonly found on beaches and deserts around the world. Similar examples to those discovered on Mars have been found in the Jurassic Navajo Sandstone near the Colorado River, Utah, where the concretions range in size from small marbles to cannonballs and consist of a hard shell of iron oxide surrounding a softer sandy interior.

They were previously thought to have formed through simple chemical reactions, but the UWA researchers used high resolution NanoSIMS (structured illumination microscope) to show clear relationships in the Utah concretions between microbe-like forms and concentrations of biological elements such as carbon and nitrogen.

They found microstructures within the Utah concretions that were consistent the remnants of bacteria, such as the iron-oxidising Gallionella.

The researchers comment that such ‘blueberries’ would make an excellent macroscopic target for the latest Curiosity Rover in its hunt for life on Mars.

The research was published in the August issue of Geology.