Dr. Wernher von Braun, the NASA Director of the Marshall Space Flight Center, explains the Saturn rocket system to President John F. Kennedy at Cape Canaveral, Florida on November 16, 1963. NASA Buzz Aldrin, the second man to walk on the moon, discovered recently that President John F. Kennedy had originally wanted to go to send Americans to Mars.

But NASA said that a Mars mission would be too difficult in the time frame that JFK was hoping for, so they suggested the US shoot for the Moon instead.

"Kennedy really wanted to go to Mars!" Aldrin told Tech Insider. "Kennedy didn't know that it was not possible. Well, very, very improbable. Just as it has been the objective of four or five presidents ever since then."

Aldrin also writes about this revelation in his new book, titled, "No Dream Is Too High," which comes out April 5.

"NASA's leader gulped hard and admitted to the president that Mars was out of reach, but the Moon might be possible within 15 years," he writes.

The book continues:

Rather than accepting what was "possible," on May 25, 1961, just three weeks after Alan Shephard's virginal flight, President Kennedy boldly challenged America to commit to the goal of landing a man on the Moon before the end of the decade! Many thought the challenge impossible to meet. We had not yet even put a man into orbit. The rockets and spacecraft that we needed to go beyond Earth's orbit didn't exist. We didn't have the know-how. But we did have a leader with a vision.

Buzz Aldrin poses with his "Get your ass to Mars" shirt. Flickr/jurvetson

A visionary leader is what Aldrin says will get us to Mars, too — fulfilling Kennedy's long ago dream. He told Tech Insider that he wants the next president to challenge the country to land humans on Mars within two decades.

That goal seems unreachable now, but if we truly had an international effort to get there, Aldrin thinks we could land humans on Mars by 2040.

As Kennedy said in his famous moonshot speech:

Many years ago the great British explorer George Mallory, who was to die on Mount Everest, was asked why did he want to climb it. He said, "Because it is there." Well, space is there, and we're going to climb it, and the moon and the planets are there, and new hopes for knowledge and peace are there. And, therefore, as we set sail we ask God's blessing on the most hazardous and dangerous and greatest adventure on which man has ever embarked.