Can you make fuel and oxygen from Mars perchlorate salts?
I’m not sure there’s enough to do anything useful with. The “high” level is probably still just a few ppm rather than a few percent, so it is of scientific, but not practical, interest. One source I found states that NASA has not yet stated how much was found, but that the total level of salts found in the soil (of which perchlorates are some fraction) is only 1000ppm (0.1 percent). Another source (not listed) gives the concentration of perchlorates in the deserts of Chile, where the compounds occur naturally on Earth, as only a few ppb. If perchlorates were present in large quantities, they would be very useful for producing oxygen – perchlorate salts release oxygen when heated (forming the chloride salt as the other product). Because they are good oxidizers, they would not be useful for making fuels, which are reducing agents. However, an oxidizing agent is an essential component of rocket propellants, sometimes termed “rocket fuel,” so they could be (and are, on Earth) used to power