One of the first men to orbit the Moon said sending people to Mars would be "stupid."
Former US astronaut William "Bill" Anders was one of the three crew members of the Apollo 8 programme.
The December 1968 mission was the first to leave Earth's orbit and complete 10 orbits around the Moon before safely returning home. It paved the way for the Apollo 11 mission which landed on the Moon just seven months later.
'What's the imperative?'
Talking to BBC Radio 5 Live which released an "Apollo 8: Christmas on the Far Side of the Moon" programme, Anders, 85, said sending crews to Mars was "almost ridiculous."
NASA is currently planning to send humans to Mars in the 2030s.
The former Navy pilot declared himself a "big supporter" of unmanned programmes "mainly because they're much cheaper."
However, he believes there is little public support to fund such vast and costly programmes.
"What's the imperative? What's pushing us to go to Mars?" he said.
"I don't think the public is that interested," he added.
Mission to Mars
NASA is developing the capabilities to send humans to an asteroid by 2025 and to Mars in the 2030s as part of the US National Space Policy issued in 2010.
Robots are already exploring Mars with NASA's Insight probe successfully landing on the Red Planet last month. The lander's mission is to study the make-up of the planet and it deployed its first instrument, a seismometer, just last week.
The interest in the Red Planet stems from the fact that its formation and evolution are comparable to Earth which could help us learn more about our planet's history and future.
Anders' former Apollo 8 teammate, Frank Borman, was more supportive of NASA's Mars programme, telling BBC Radio 5 Live: "I firmly believe that we need robust exploration of our Solar System and I think man is part of that."
However, he was more critical of private ventures.
Elon Musk's SpaceX and Amazon CEO Jeff Bezos' Blue Origin have both included manned missions to Mars in their long-term goals.
SpaceX even said in October that it plans to send its first cargo mission to Mars in 2022 with a second mission, with both cargo and crew, scheduled for 2024.
For Borman however, "there's a lot of hype about Mars that's nonsense."
"Musk and Bezos, they're talking about putting colonies on Mars, that's nonsense," he added.