Elon Musk announced on Monday that his company is working on a program to take carbon dioxide (CO2) out of the atmosphere and convert it into rocket fuel, claiming that it will be important for his future missions to Mars. Musk announced the news on Twitter and invited people to participate in the program, writing: “SpaceX is starting a program to take CO2 out of atmosphere & turn it into rocket fuel. Please join if interested.” “Will also be important for Mars,” he added. The Tesla chief executive did not elaborate further on the new sustainable fuel program but as per the company’s website, the SpaceX Falcon 9 rocket uses rocket-grade kerosene (RP-1) propellant as fuel. According to Tesla, Falcon 9 is the world’s first orbital-class reusable two-stage rocket designed to safely transport people and payloads into Earth orbit and beyond. Tesla says its reusability allows SpaceX to re-fly the most expensive parts of the …