HELSINKI — China is inviting interested parties to submit proposals to join the country’s pioneering Mars sample return mission, due to launch in late 2028. The China National Space Administration (CNSA) published an announcement of opportunities March 11, officially opening the Tianwen-3 Mars mission to international cooperation. Tianwen-3 aims to collect samples from Mars and, for the first time ever, deliver them to Earth. The primary scientific goal is the detection of potential biosignatures and answering a fundamental question: has life ever existed on Mars? “This opportunity is open to the global community. International partners are welcome to collaborate with...