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Scientists are excited over the latest geological evidence for the existence of life on Mars. But as we have seen many times in the past, the Red Planet guards its secrets closely with the possibility of non-life explanations for the formations.
As geologist Joel Hurowitz said in our recent conversation on Quirks & Quarks, the rock in question was found by the Perseverance rover that has been exploring what was once a river delta that drained into an ancient Martian lake.
Two chemicals found in the delta, vivianite and greigite, are most often formed on Earth by microbial activity in the soil — hence the excitement. But under certain conditions, they can also be formed by chemical reactions. In other words, we have potential evidence for life on Mars, but no conclusive proof.
NASA's Perseverance rover discovered spots on reddish rock in July 2024 that scientists are considering as a potential biosignature for life. (NASA/JPL-Caltech/MSSS)
Mars has been tantalizing us with the possibility of life on its surface since American astronomer Percival Lowell looked through his telescope in 1894 and thought he saw straight lines crisscrossing the planet.
He called them canals, which are artificial, not naturally formed channels. Lowell believed these enormous features were engineered like the Panama or Suez Canals, but on a much larger scale. To him it suggested there was a civilization on Mars with amazing technical skills.
It was not until the late 1960s, when robots were finally sent to Mars that we got the first closeup images of the surface and saw that the there was evidence of channels but not canals. (NASA's Mariner 9 orbiter)
Lowell's claims were fuel for science fiction writers and movie makers, leading to stories such as H.G. Wells' War of the Worlds, where Earth is invaded by benevolent Martians.
It was not until the 1970s that robotic spacecraft sent to Mars debunked Lowell's theory, revealing a landscape pockmarked with craters that looked more like the moon than a habitable planet.
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