In February of next year, the NASA Perseverance Rover will land on Mars in the Jezero Crater. Soon after its landing, it will begin to gather soil samples that will be returned to earth for study a little more than a decade later. Scientists are hoping that they can find evidence of past life on Mars hidden in the soil samples.
However, scientists have a new concern that they fear could have destroyed any evidence in the Martian soil of past life on the planet. That concern is acidic fluids. Acidic fluids once flowed on the Martian surface and may have destroyed biological evidence hidden within the iron-rich clay on the planet’s surface. Researchers conducted simulations involving clay and amino acids to draw their conclusions.
In the search for life on the Red Planet, it’s clay surface soils are the preferred collection target. Scientists say that the clay protects the molecular organic material inside. However, the presence of past acidic fluids on the surface could compromise the clay’s ability to protect evidence of past life. Researchers say that the internal structure of clay is organized into layers where the evidence of biological life, such as lipids, nucleic acids, peptides, and other biopolymers, may be trapped and preserved.
In laboratory simulations of Martian surface conditions, researchers tried to preserve an amino acid called glycine in clay that had been previously exposed to acidic fluids. After a long exposure to ultraviolet radiation similar to what Mars’ surface is exposed to, experiments showed photodegradation of glycine molecules embedded in the clay.
Researchers found that exposure to acidic fluids erases the clay’s interlayer space transforming it into gel-like silica. The experiment showed that when glycine is exposed to acidic fluid, the layers collapse, and organic matter can’t be preserved. Researchers say that the tests show why searching for organic compounds on Mars is so difficult.