Robert Zubrin

"It is very unlikely that we would drive to extinction any native Martian microorganisms in the process of extending the habitability of Mars."

"We do not need a lunar-orbiting station to go to the Moon. We do not need such a station to go to Mars. We do not need it to go to near-Earth asteroids. We do not need it to go anywhere. Nor can we accomplish anything in such a station that we cannot do in the Earth-orbiting International Space Station, except to expose human subjects to irradiation – a form of medical research for which a number of Nazi doctors were hanged at Nuremberg"

"Musk can probably build a giant AI data centre on the Moon. But if it can’t compete with much cheaper alternatives on Earth, it could prove a financial disaster that collapses his credibility, and with it his entire corporate empire"