US president John F Kennedy had originally wanted to go to Mars, not the Moon, but engineers had to tell him the Red Planet was just a "little bit too far", Buzz Aldrin has revealed. The second man on the Moon told the ASFA 2015 National Conference in Brisbane about JFK's ambitious plan during a speech about how the US and China should work together on space exploration projects.

Aldrin told the superannuation conference how he had only recently learned about Kennedy's initial plans for space exploration, the Sydney Morning Herald reports. "Nasa told him it would take at least 15 years before we could put a man on the Moon," Aldrin said. "Now, I recently learnt at MIT (the Massachusetts Institute of Technology) at the 100th anniversary of the aero/astro school department, that Kennedy had actually wanted us to go to Mars.

"He asked his engineers to figure it out and, after a weekend of rather intense calculations, they told him that Mars was just a little bit too far to go, but we could shoot for the Moon as a more realistic goal. Can you imagine having only one weekend to figure that out for the president?"

Neil Armstrong and Aldrin would become the first humans on the Moon in 1969, eight years after Kennedy addressed the US congress with his famous 1961 Moon speech. "I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the moon and returning him safely to the Earth," he said. "No single space project in this period will be more impressive to mankind, or more important for the long-range exploration of space; and none will be so difficult or expensive to accomplish."

Aldrin said that instead of accepting it would take 15 years to reach the Moon, Kennedy challenged the US to commit to the challenge of reaching this goal in just nine years. "We had not even put a man into orbit," Aldrin said. "The rockets and spacecraft needed to go beyond Earth's orbit didn't exist.

"Many thought the challenge to be impossible. We didn't have the know-how, but we did have a leader with the vision, the determination and the courage – and the confidence – that we could get there. By publicly stating our goal, putting a specific time period on a very specific achievement, President Kennedy gave us no way to back out."

Aldrin said the current US administration should "open the door" to China to expand space exploration, as it would make for better relations and greater innovation: "By venturing into space, we improve life for everyone here on Earth. We really should work with [China] in space and I believe that will help down here," he said.

"Things may not work out the way they think they will. But if they were to just open the door a little bit, to relations with China and space, someone else will make it work and they will get credit for it."