Photo: NASA/Dan Gallagher
Scientists have found some of the most convincing evidence yet that life could have formed on Mars. The discovery comes from organic molecules detected in rock samples from the Gale Crater, suggesting they may not be explained solely by non-biological processes. Researchers say it is “reasonable to assume” that living organisms could have produced these unusual molecules, according to Live Science.
The molecules, called alkanes, were found in the fine-grained sedimentary rock known as Cumberland mudstone, formed on the floor of the ancient lake Yellowknife Bay. The Curiosity first drilled this rock in 2013, but the largest organic molecules were only identified about a year ago when the rock was heated to 1100°C during a search for amino acids.
Using mathematical modeling, data from Curiosity, and laboratory experiments on how radiation breaks down molecules over time, scientists extrapolated how abundant these organics might have been billions of years ago. Despite exposure to harsh radiation on Mars for roughly 80 million years, the original concentration of alkanes—or their fatty acid precursors—was estimated to be between 120 and 7,700 parts per billion.
Researchers considered possible non-biological ways the molecules could form and concluded that only formation in hydrothermal systems, later transported to the surface by water, was plausible. Additional evidence supports a potentially habitable environment: clay minerals that form in water, nutrient nitrates linked to biological activity, and sulfur, which helps preserve organics.
The long-term presence of water in Gale Crater likely allowed chemical processes to mix and combine molecules over millions of years, creating conditions that could have supported life.
