Clues to Life on Mars in a Polluted California Mine

By Becky Oskin

To find evidence of life on Mars, scientists from UC Davis and the U.S. Geological Survey are chasing clues in Mars-like environments on Earth.

Pollution at the disused Iron Mountain mine near Redding, Calif. turns the soil red and makes the environment Mars-like. Amy Williams, Towson University

The environment at the Iron Mountain mine near Redding, Calif. is similar to Mars. Amy Williams, Towson University

The researchers hope to find rock patterns and textures that are uniquely linked to microscopic life such as bacteria and algae. “It’s challenging to prove that a mineral was made by a living organism,” said lead study author Amy Williams, an assistant professor at Towson University in Towson, Maryland. Williams led the research as a graduate student at UC Davis. Finding similar textures in Mars rocks could bolster confidence that microscopic shapes in Red Planet rocks were formed by living creatures.

Williams’ search centered on an extreme environment — the polluted water and soil at Iron Mountain, a shuttered mine near Redding, California. Originally a copper mine, the water and soil at Iron Mountain are stained red by iron, creating a landscape much like the one on Mars today.

“Iron Mountain is a sensational Mars analog site,” Williams said.

At Iron Mountain, the research team has discovered tiny filaments made of a form of iron oxide, or rust, surrounding microscopic organisms. The structures form around bacteria as the microbes munch on iron, leaving behind thread-like tubes that preserve the creature’s shapes. The tiny tubes could help narrow down the search for remnants of ancient life. For instance, similar microbial filaments could be preserved on Mars in an environment similar to Iron Mountain, with the Hematite Ridge in Gale Crater as tentative possibilities, the researchers said.

Scanning electron microscope images of bacterial filaments from Iron Mountain mine. These bacteria could help identify fossil microbes on Mars. Amy Williams, Towson University

Scanning electron microscope images of bacterial filaments from Iron Mountain mine. These bacteria could help identify fossil microbes on Mars. Amy Williams, Towson University

“This research is a step forward in understanding how to search for fossil life on Mars,” Williams said.

Other study authors include UC Davis professor Dawn Sumner, a member of NASA’s Mars Science Laboratory team, and USGS scientists Charles Alpers and Kate Campbell.

The findings were published March 2017 in the Geomicrobiology Journal.

Becky Oskin writes for the Division of Mathematical and Physical Sciences, College of Letters and Science. Follow her on Twitter @beckyoskin.

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