Detecting Fossilized Life on Mars


Curiosity Rover


“This should be an easy form of fossilized life for a rover to detect on other planets. If we see this kind of extensive filamentous rock on other planets, we would know it’s a fingerprint of life,” said University of Illinois geology professor Bruce Fouke, who led a new, NASA-funded study of bacterium that controls the formation of such rocks on Earth that thrives in harsh environments similar to harsh conditions on Mars. “It’s big and it’s unique. No other rocks look like this. It would be definitive evidence of the presences of alien microbes.”

The bacterium belongs to a lineage that evolved prior to the oxygenation of Earth roughly 2.35 billion years ago, Fouke said. It can survive in extremely hot, fast-flowing water bubbling up from underground hot springs. It can withstand exposure to ultraviolet light and survives only in environments with extremely low oxygen levels, using sulfur and carbon dioxide as energy sources.

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“It has an unusual name, Sulfurihydrogenibium yellowstonense,” he said. “We just call it ‘Sulfuri.’ Taken together, these traits make it a prime candidate for colonizing Mars and other planets,” Fouke said.


Mars Travertine Rock


And because it catalyzes the formation of crystalline rock formations that look like layers of pasta, it would be a relatively easy life form to detect on other planets, he said.

A self-portrait of NASA’s Curiosity Mars rover above shows the robot at a drilled sample site called “Duluth” on the lower slopes of Mount Sharp.

The unique shape and structure of rocks associated with Sulfuri result from its unusual lifestyle, Fouke said. In fast-flowing water, Sulfuri bacteria latch on to one another “and hang on for dear life,” he said.

“They form tightly wound cables that wave like a flag that is fixed on one end,” he said. The waving cables keep other microbes from attaching. Sulfuri also defends itself by oozing a slippery mucus.

“These Sulfuri cables look amazingly like fettuccine pasta, while further downstream they look more like capellini pasta,” Fouke said. The researchers used sterilized pasta forks to collect their samples from Mammoth Hot Springs in Yellowstone National Park.

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The team analyzed the microbial genomes, evaluated which genes were being actively translated into proteins and deciphered the organism’s metabolic needs, Fouke said.

The team also looked at Sulfuri’s rock-building capabilities, finding that proteins on the bacterial surface speed up the rate at which calcium carbonate—also called travertine—crystallizes in and around the cables “1 billion times faster than in any other natural environment on Earth,” Fouke said. The result is the deposition of broad swaths of hardened rock with an undulating, filamentous texture.

The Daily Galaxy via University of Illinois at Urbana-Champaign

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