Criticism
Mars One received a variety of criticism, mostly relating to medical, technical and financial feasibility. There were also unverified claims that Mars One was a scam designed to take as much money as possible from donors, including reality show contestants. Many criticized the project's US$6 billion budget as being too low to successfully transport humans to Mars, to the point of being delusional. A similar project study by NASA estimated the cost of such a feat at US$100 billion, although that included transporting the astronauts back to Earth. Objections had also been raised regarding the reality TV project associated with the expedition. Given the transient nature of most reality TV ventures, many believed that as viewership declined, funding could significantly decrease, thereby harming the entire expedition. Further, contestants reported that they were ranked based on their donations and funds raised.
Academia
John Logsdon, a space policy expert at George Washington University, criticized the program, saying it appeared to be a scam and not "a credible proposition".
Chris Welch, director of the Masters Programs at the International Space University, said "Even ignoring the potential mismatch between the project income and its costs and questions about its longer-term viability, the Mars One proposal does not demonstrate a sufficiently deep understanding of the problems to give real confidence that the project would be able to meet its very ambitious schedule."
Gerard 't Hooft, theoretical physicist and Mars One ambassador, has stated that he thought both their proposed schedule and budget were off by a factor of ten. He said he still supported the project's overall goals.
A space logistics analysis conducted by PhD candidates at the Massachusetts Institute of Technology (MIT) revealed that the most optimistic of scenarios would require 15 Falcon Heavy launches that would cost approximately $4.5 billion. They concluded that the reliability of Environmental Control and Life Support systems (ECLS), the Technology Readiness Levels (TRL), and in situ resource utilization (ISRU) would have to be improved. Additionally, they determined that if the costs of launch were also lowered dramatically, together this would help to reduce the mass and cost of Mars settlement architecture. The environmental system would result in failure to be able to support human life in 68 days if fire safety standards on over-oxygenation were followed, due to excessive use of nitrogen supplies that would not then be able to be used to compensate for leakage of air out of the habitat, leading to a resultant loss in pressurization, ending with pressures too low to support human life. Lansdorp replied that although he has not read all the research, supplier Lockheed Martin said that the technologies were viable.
Another serious concern uncovered in the research conducted by MIT was replacement parts. MIT PhD candidates estimated the need for spare parts in a Mars colony based on the failure rates of parts on the International Space Station. They determined that a resupply mission every two years would be necessary unless a large space in the initial launch were to be reserved for extra materials. Lansdorp commented on this saying, "They are correct. The major challenge of Mars One is keeping everything up and running. We don't believe what we have designed is the best solution. It's a good solution."
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In March 2015, one of the Mars One finalists, Joseph Roche, stated to media outlets that he believed the mission to be a scam. Roche holds doctorate degrees in physics and astrophysics, and shared many of his concerns and criticisms of the mission. These claims include that the organization lied about the number of applicants, stating that 200,000 individuals applied versus Roche's claim of 2,761, and that many of the applicants had paid to be put on the list. Furthermore, Roche claimed that Mars One was asking finalists for donations from any money earned from guest appearances (which would amount to a minimal portion of the estimated $6 billion required for the mission). Finally, despite being one of 100 finalists, Roche himself never spoke to any Mars One employee or representative in person, and instead of psychological or psychometric testing as is normal for astronaut candidates (especially for a lengthy, one-way mission), his interview process consisted of a 10-minute Skype conversation.
Space advocacy and policy
Robert Zubrin, advocate for crewed Martian exploration, said "I don't think the business plan closes it. We're going to go to Mars, we need a billion dollars, and we're going to make up the revenue with advertising and media rights and so on. You might be able to make up some of the money that way, but I don't think that anyone who is interested in making money is going to invest on that basis – invest in this really risky proposition, and if you're lucky you'll break even? That doesn't fly." Despite his criticisms, Zubrin became an adviser to Mars One on 10 October 2013.
Astronauts
Canadian former astronaut Julie Payette said during the opening speech for an International Civil Aviation Organization conference that she did not think Mars One "is sending anybody anywhere".
In January 2014, German former astronaut Ulrich Walter strongly criticized the project for ethical reasons. Speaking with Tagesspiegel, he estimated the probability of reaching Mars alive at only 30%, and that of surviving there more than three months at less than 20%. He said, "They don't care what happens to those people in space... If my tax money were used for such a mission, I would organize a protest."
Space tourist Richard Garriott stated in response to Mars One, "Many have interesting viable starting plans. Few raise the money to be able to pull it off."
Former US astronaut Buzz Aldrin said in an interview that he wants to see humans on Mars by 2035, but he does not think Mars One will be the first to achieve it.
Publications
Wired magazine gave it a plausibility score of 2 out of 10 as part of their 2012 Most Audacious Private Space Exploration Plans.
The project lacked current funding as well as sources for future funding. The organization had no spacecraft or rocket in development or any contracts in place with companies that could provide a spacecraft or rocket. While plans point to SpaceX for both resources, the company had no contracts with Mars One in an industry that typically plans contracts decades in advance.
