﻿He is not the first person to express scepticism about Mars One, a vastly ambitious private mission aiming to settle humans on Mars from 2025. But Joseph Roche is different from most critics: he’s on the shortlist of astronauts. 
Roche, an astrophysicist at Trinity College Dublin who was announced in February as among the 100 people in line for the mission, has written for the Guardian expressing his grave doubts about the viability of Mars One. 
The selection process, Roche writes, “was not rigorous enough to reach the requisite standard of more traditional astronaut selection programmes”. He also says the Dutch Mars One team have displayed “a certain naivety” in believing they can succeed alone in the supposed $6bn mission and should now accept it is very unlikely to happen. 
He writes: “More openness and transparency would benefit Mars One greatly but I think that the shortcomings of the selection process, coupled with their unwillingness to engage and collaborate with the scientific community mean that the time might have come for Mars One to acknowledge the implausibility of this particular venture and turn their efforts towards supporting other exciting and more viable upcoming space missions.” 
Roche also expressed worries about the way the mission organizers publicized a so-called top-ten candidates. The ranking, he said, didn’t mean these were the most likely potential astronauts but was, instead, based on how many “supporter points” each had earned through acts such as buying official merchandise.