The findings are suggestive but still not conclusive. The photos are from the Gillespie Lake outcrop in the Martian Yellowknife Bay, a dry lakebed that was subject to seasonal flooding some 3.7 billion years ago. Mars was much warmer and contained liquid water at the time, with conditions possibly hospitable to life as we know it.
The photos show structures like those produced by colonies of microbes that trap and rearrange sediments in water bodies like lakes and coastal bays. The distinctive features thus formed can fossilize and are known as microbially-induced sedimentary structures (MISS). MISS might be the oldest signs of life on our planet — up to 3.48 billion years old — as reported last year, when they were found in Australia’s Dresser Formation.
The Australian MISS discovery came from Nora Noffke, a geobiologist at Old Dominion University in Virginia, who has 20 years of experience with MISS. Noffke also noticed the strong similarities between MISS and the Martian structures, and details here analysis in a paper in the journal Astrobiology, published in December, 2014.
Chris McKay, planetary scientist at NASA’s Ames Research Center, was skeptical but appreciative however. “I’ve seen many papers that say ‘Look, here’s a pile of dirt on Mars, and here’s a pile of dirt on Earth… and because they look the same, the same mechanism must have made each pile on the two planets”, he said.
“All I can say is, here’s my hypothesis and here’s all the evidence that I have,” Noffke says, “although I do think that this evidence is a lot.”
