In August 2018, Musk shared a 1993 research paper that claimed humans could release the stores, walk around Mars with just a breathing apparatus, and ditch the need for a spacesuit.
Edwards of Northern Arizona University found in August 2018 that Mars may only have enough carbon dioxide to create an atmosphere of 15 millibars.
Chinese billionaire Jack Ma clashed with Musk in August 2019 over the plans, which could cost up to one percent of global gross domestic product, declaring that Earth "needs more heroes."