The soil on Mars is filled with chemical compounds that make short work of organic compounds. Yet NASA remains hopeful about finding signs of life on the Red Planet, so the agency developed an experiment for a future Mars mission that can detect amino acids, an article in Space.com stated.
Amino acids are considered to be a sign of life. When NASA’s Phoenix Mars lander touched down on the planet’s surface, one of its missions was to take soil samples and analyze them for the presence of organic compounds.
Yet the lander found no signs of amino acids in the alkaline soil. Researchers eventually realized that the soil samples contained a large amount of perchlorate (ClO4). This highly reactive chemical serves as an explosive and fuel propellant on Earth.
It so happens that the equipment aboard the Phoenix Mars tests for organic compounds using pyrolysis. The process involves high temperatures, which heated the perchlorate and caused it to burn up any organics in the vicinity.
This complication called for a different means of testing for organic compounds. The tool needed to be sufficiently sturdy for the long trip to Mars and able to circumvent the perchlorate problem. (Related: Why did Mars dry out? NASA space telescope reveals insights.)
Researcher Aaron Noell from NASA’s Jet Propulsion Laboratory (JPL) recently published a paper on subcritical water extraction (SCWE) as an alternative to pyrolysis. He likens the seemingly complicated process to making a cup of Martian espresso.
Noell explained that his proposal uses pressurized hot water instead of pyrolysis. The method takes advantage of amino acids being soluble in water.
The JPL experiment tested SCWE’s effectiveness on three different soil samples from Earth – with one containing perchlorate salt to simulate Martian soil – plus a control. The technique was used at different temperatures and for varying lengths of time.
Noell reported that the method successfully detected high levels of terrestrial amino acids in the soils. SCWE also preserved most of those organic compounds, even in the presence of perchlorate salt like those found in Mars.
Tufts University chemistry professor Samuel Kounaves was involved with the Phoenix Lander’s chemistry equipment. While not a part of the JPL team, he remarked that SCWE showed promise as an alternative means of studying Martian soils.
Using water as a solvent simplifies storage and transportation. Unlike the chemicals used in pyrolysis, water is non-corrosive and safe. Matter extracted using the liquid is also easier to work with.
Kounaves recommended further experiments subjecting SCWE to much higher temperatures that improve the solubility of bigger organic molecules. Higher heat levels would also better simulate the full impact of the perchlorate.
In addition, experiments with simulant soils that are much closer to Martian regolith would refine the new method.
Study author Noell says that the properties of water change as the temperature goes up. SCWE is therefore not limited to testing for amino acids. It could also extract the more complicated organic compounds like long-chain fatty acids and polycyclic aromatic hydrocarbons.
A single extraction solvent could be used to process many different compounds from soil. This dispenses with other potentially volatile chemicals and frees up valuable weight and room on the spacecraft.
Furthermore, using higher temperatures for SCWE can break apart polypeptides into the simple amino acids that comprise them. Researchers can figure out the origin of those amino acids, which would let them determine the possibility of life based on these potential building blocks for life.
You can read more articles about the payloads of future missions to Mars at Space.news.