A NASA-supported scientist is studying how carbon dioxide—the main gas in the Martian atmosphere—can be used to make rocket fuel and water from the Red Planet.
When astronauts first arrive on Mars, it will be difficult to deliver supplies containing all the things they need to survive. Even the first journey may last up to two years - however spaceships can only carry a limited amount of supplies. "We may do what explorers have done for generations: live off what the earth offers us," said chemical engineer Ken Debelak of Vanderbilt University.
Researchers on Earth usually rely on what they find in the field. The animals may be strange but they will be there and they can be eaten. But the challenge is the same challenge. Astronauts will want to pull what they can from the planet itself. Although the goal seems improbable, Dublac believes that it is achievable. He is working on a NASA project that will allow it to be realized. The key, he says, lies in the atmosphere of Mars. The atmosphere of Mars is very thin compared to that of the Earth and contains 95 percent carbon dioxide (CO2). However, it seems that the disadvantage can be turned into an advantage .
The carbon dioxide, says Deblak, can be used as a raw material for many products. In the rocky soil of Mars, useful ingredients are hidden: magnesium and hydrogen for jet fuel, oxygen for breathing, water for drinking, all that is needed is soluble to bring them out, and then it turns out that carbon dioxide comes to the rescue. "When carbon dioxide is compressed to 73 atmospheres and heated to 31.1 degrees Celsius it becomes a supercritical liquid and excellent solubility." Dublak said.
A supercritical fluid is at high pressure and high temperature. This is a state of aggregation that may be described as a liquid-like gas. Almost anything can become super critical. Water for example becomes a supercritical fluid at high pressure and temperatures in steam turbines. Normal water is excellently soluble. Supercritical water is super soluble, maybe even too good. They even melt the tips of the turbine blades. Carbon dioxide in the supercritical state does about the same action. CO2 molecules flow into solid matter, surround atoms, push them and separate them.
Phase diagram: the critical point, highlighted with a large green dot, is a special combination of temperatures (Tc=31 C) and pressure (Pc=73 atm) where the properties of CO2 are both gas and liquid. Above the critical point, the material becomes a supercritical fluid.
On Earth, CO2 is not used too much in supercritical mode to melt materials because there are cheaper and more efficient methods at hand. It is used, for example, to break down caffeine from coffee beans, and sometimes also to dry clean clothes. On Mars, Deblak believes, CO2 will play a much more important role. For example, magnesium can be melted easily with supercritical C02. Find Dublac. "It's an experiment we're pretty excited about right now." saying. Magnesium, which is almost certainly found in the Martian soil, is easily ignited and can be used as rocket fuel. In fact, Deblak says, one of the scenarios for landing on Mars suggests building an entire lander out of magnesium, including the landing legs. "When the astronauts are ready to return home they will be able to load these parts into the engine, add oxidizers to ignite the mixture.
"By using CO2 as a solvent, the magnesium could be used as a fuel, and it could be extracted from Mars." Supercritical CO2 may also be used to produce water. Some rocks on Mars, as well as some types of rocks on Earth, contain hydrogen. "When these rocks are immersed in supercritical carbon dioxide, a chemical reaction occurs. The carbon in the CO2 is fixed in the rock, and it leaves the oxygen free to find another partner - hydrogen. "The result of this dissolution is water," says Dublak. "You can use it to make water "Extracting water from the rock will be one of the most profitable things, at least in the short term, said Deblak. In addition to drinking, it will be possible to extract the hydrogen back from the water for fuel and the oxygen that will be separated will be used for breathing - or as an oxidizer for some type of engine. "Eventually, the settlers will be able to plant plants which use the carbon dioxide in the Martian atmosphere to create hundreds of kilograms of raw material per day. A supercritical fluid has several advantages over other solvents: its solubility changes dramatically when temperatures or pressure are changed. You can control the process so that sometimes it is a solvent for certain purposes and sometimes it is not. This allows the dissolved materials to be recovered. For example, if you want to recover the caffeine you removed from the coffee beans (caffeine recovered from the decaffeinated coffee industry is used for soft drinks), you simply need to lower the pressure of the CO2 and the caffeine falls out.
At present, Dublak is trying to map all types of behavior of the supercritical CO2. He checks which minerals can dissolve easily and which cannot, and how the solubility can be improved. Adding other ingredients to CO2 sometimes helps. saying. Dublak's work can also be useful on Earth. Carbon dioxide is in the spotlight because of its role in global warming. However, as a solvent, it is useful. Many solvents used in industry are toxic. They cause cancer and if they get into the water system, they stay there for a long time. Therefore it is of interest to study how C02 can be used as a green alternative. Carbon dioxide plays a different role on Earth and Mars. "That's what's intriguing." Deblak emphasizes.
"The Martian environment is a foreign environment to ours. The laws there are different." "Therefore, this is what we are doing - trying to find out what the laws are," he said. Then we can determine how to play the game, on both planets."
