With all of the media buzz about going back to the moon, the latest news being SpaceX’s plans to send two unidentified well-heeled and adventurous people around the moon, inevitably a human being who had actually been there would weigh in. Buzz Aldrin, the second man to walk on the moon, seemed, at first, to be singularly unimpressed with the idea, according to a CBS affiliate in San Francisco.

Aldrin tweeted to SpaceX CEO Elon Musk, “Been there, done that. I prefer Get Your Ass to #Mars.”

About ten minutes later, Aldrin thought the better of it and added, “Actually @elonmusk I support space tourism & there are many useful things we can do at the moon such as an Int'l moon base mining the ice.”

Aldrin has been conducting a campaign to get humans to Mars for many years.

The obsession was so keen that seven years ago the former Apollo moonwalker allowed himself to be made into a political prop by then President Barack Obama when he flew down to the Kennedy Space Center to announce what eventually became the Journey To Mars.

Musk is a big Mars enthusiast as well, recently rolling out his long term plan to build a city on the Red Planet, using a huge rocket capable of taking 100 people across the interplanetary gulfs at a time. Musk also plans to send a version of his company’s spacecraft, the Red Dragon, to the Martian surface in a mission that just got delayed from 2018 to 2020. He has also suggested that he can send the first people to Mars in the middle of the 2020s, years before NASA plans to.

Musk has a tendency to make promises like that which are not always followed through on.

Aldrin’s back and forth about Mars vs. the moon is a typical behavior in aerospace circles. Many want to go to Mars directly, the sooner the better. But then the realization dawns that lunar ice can be refined into rocket fuel, useful for a campaign of Mars exploration and eventual settlement. The Journey to Mars has a refueling stop at the moon, as it turns out, and that means going there first.