It's been years that the President of the United States of America Barack Obama says that US must send human to Mars, permanently.

On his 2010 speech, he said that by the mid-2030s, US can send humans to orbit Mars and return them safely to Earth. He added that the landing on Mars will follow and he expect to be around to see it.

There was also a time in 2012 when he said the Curiosity rover was inspiring kids to tell their moms and dads they want to be part of a Mars mission - maybe even the first person to walk on Mars. And there were those times he told the kids visiting the White House that they might go to Mars.

Lately, in his 2015 State of the Union address, he told the U.S. to push out into the solar system not just to visit but to stay.

Today, President Obama said it again in an op-ed published by CNN that we have set a clear goal vital to the next chapter of America's story in space: sending humans to Mars by the 2030s and returning them safely to Earth, with the ultimate ambition to one day remain there for an extended time.

Some commercial spaceflight companies have also announced plans to aim for Mars in the upcoming decades.

A Dutch venture called Mars One hopes to colonize Mars by 2025, and has been taking applications from would-be travelers for years, though it acknowledges that it will rely on "major aerospace companies" for transportation.

Musk predicted any Mars mission would require "a huge public-private partnership."

"Pronouncements by multiple presidents of bold new ventures by Americans to the Moon, to Mars, and to an asteroid in its native orbit, have not been matched by the same commitment that accompanied President Kennedy's now fabled 1961 speech," a 2014 report by the National Research Council.

This coming week, Obama will host the White House Frontiers Conference in Pittsburgh, where the White House says the five "frontiers of innovation" up for discussion are personal, local, national, global and interplanetary.