Mars mission: is Musk's promise a serious plan or a marketing stunt?

Commentators are increasingly questioning whether Elon Musk's plan to send humans to Mars is a genuine goal or another marketing ploy. Musk has built an image as someone offering liberation from state telecoms, fossil fuels and media censorship — with himself holding the key to all of those doors. Critics argue the Mars mission was never a serious plan, but rather a clever branding device.