In 2001, Elon Musk visited NASA's website to find information on manned missions to Mars... and came up empty.

The year in which the science fiction classic 2001: A Space Odyssey took place looked very different in reality, and Musk realized that the Space Race had been, as he told Aeon's Ross Anderson, "a transient Cold War phenomenon, a technological pissing match fuelled by unsustainable public spending."

This realization is what spurred Musks' desire to plan a Mars mission of his own — but not the manned mission and human colony you are thinking of.

Anderson writes:

Aghast at this backsliding, and still thinking it a failure of will, Musk began planning a Mars mission of his own. He wanted to send a greenhouse to Mars, filled with plants that would become, in the course of their long journeying, the most distant travellers of all multicellular life. Images of lush, leafy organisms living on the red planet would move people, he figured, just as images of the Earth rising, sunlike, on the lunar plain had moved previous generations.

He was hoping that seeing plants living on Mars would help spur humanity's engagement with space, therefore and NASA's budget. So, he started looking for ways to get his greenhouse plan to space. NASA's concept art for a greenhouse on Mars. Science.nasa.gov The problem? As Anderson writes:

When Musk went to price the mission with US launch companies, he was told transport would cost $60-80 million. Reeling, he tried to buy a refurbished Russian intercontinental ballistic missile to do the job, but his dealer kept raising the price on him.

None of these deals worked out, so Musk founded SpaceX and started building his own rockets to one day send his green house, and eventually, people to space, and then to Mars.

Now, Musk's goal is to create a whole colony, of a million people, on Mars. While Musk has deviated from his original plan to grow plants on Mars, NASA may be taking up that calling: There's a plan in place to put a greenhouse on Mars in 2021, according to Space.com.

SpaceX on the other hand, has plenty to do closer to Earth, with regular cargo missions going to the International Space Station, and a recent contract to send up manned flights for the first time since the retirement of the Space Shuttle.