Curiosity gets most of the press these days as the preeminent Martian rover. But both Spirit and Opportunity did a great deal of scientific exploration before their newer cousin arrived on the Red Planet. Back in 2008, Spirit gathered information on some distinctive rocks near Home Plate in Gusev Crater. Analysis showed that the rocks in question were made from silica.
Close up, the rocks have a distinctive cauliflower-like shape, which is where the nickname came from. There’s nothing unusual about finding rocks with a high silica (SiO2) content; they’re common in volcanic environments, particularly hot springs. As UniverseToday discusses, you can find these silica deposits all across Earth, including some impressive specimens at Yellowstone National Park.
Here’s where things get interesting. There’s nothing unusual about silica rich deposits, but on Earth, those deposits are home to microbial life. On Earth, microbes shape the silica deposits into distinctive shapes that at least superficially resemble those seen above.
The research paper, by Steven Ruff and Jack Farmer of Arizona State University, notes that the formations found on Mars are visually similar to those found in the Atacama Desert here on Earth. That’s considered significant for two reasons. First, because the Atacama is the driest places on our planet with temperatures that alternate between freezing and boiling and a higher level of UV than most other locations. As a result, it’s often used as an environmental proxy for conditions on Mars. Second, because the Atacama is teeming with microbial life, which could tell us something about how effectively life survived on the Red Planet.
Until we can actually examine the structures in question, there’s no hard proof that the unusual rock formation was produced by biological organisms. On Earth, we know that living creatures are responsible for the formations, but that doesn’t rule out non-biological processes. Mars, after all, is an entirely different planet. One could even argue that modern day scientists seeing biology in such phenomena are making a mistake similar to astronomers like Percival Lowell, who believed the Martian features first glimpsed by Giovanni Schiaparelli in 1877 actually were canals.
To be fair, modern-day scientists are often more tempered in their comments than in some of the remarks their counterparts made a century and more ago. These new discoveries are couched in caution — structures could be explained by biological processes, but are by no means certain to have been produced by such. Even so, discovering that ancient microbes did inhabit Mars could be proof of a recent Great Filter hypothesis — specifically that life may be abundant and arise often, but that it only manages to establish itself and begin modifying a planet to remain hospitable to life in a handful of cases.
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