Last week, famed physicist Stephen Hawking threw himself into the headlines with the declaration that humanity has, in his estimation, roughly 100 years to figure out how it's going to colonize other worlds. Past that deadline, calamities ranging from climate change to asteroid strikes could put a swift end to our existence.

It's grim predictions like this one that likely keep former astronaut Buzz Aldrin awake at night wondering why we aren't moving faster with creating another lifeboat for humanity. For several years now, the 87-year-old (who in 1969 became the second person to walk on the moon), has been touring the world and sharing thoughts on the colonization of Mars. In 2015, he even submitted a master plan to NASA in collaboration with the Florida Institute of Technology outlining the creation of a human Mars outpost by 2040.

"It is in our DNA, our makeup as human beings, to have a curiosity to expand our knowledge and to explore beyond the present limits," he told From The Grapevine. "It is an inevitable mark of progress."

As Aldrin is well aware, turning humanity into a two-planet species will require not only a great deal of innovation but an equally large investment. Speaking at the Humans to Mars Summit in Washington on May 9, he encouraged NASA to narrow its focus on the red planet.

"We can afford to go to Mars, but we must have fiscal discipline," he said. "We must focus our limited resources on only those things that are really necessary to get to Mars. In my view, we are currently spending over $6 billion on programs we do not need to get to Mars. We need reusability, every element of the system."

One giant piece of NASA's budget Aldrin would like to see repurposed is the billions it spends annually towards the International Space Station.

"We must retire the ISS as soon as possible," he said. "We simply cannot afford $3.5 billion a year of that cost."

NASA itself is keenly aware that it will either need a larger budget or will have to choose between its low-Earth orbit endeavors and deep space exploration. As it stands, the ISS currently serves as an important testbed for technologies that may one day help us colonize other worlds. Its continued costs, however, delay ever further the space agency's ability to become laser-focused on sending humans to other worlds.

"Tax-dollars spent on the ISS will not be spent on destinations beyond low-Earth orbit, including the moon and Mars," Rep. Brian Babin (R-Texas), chairman of the House Committee on Space, said during a hearing to discuss the future of the ISS in February. "What opportunities will we miss if we maintain the status quo?"

Plotting a Mars pivot

According to Aldrin, the future of the ISS and other low-Earth operations may be best left to private interests. The dramatic rise of companies like Blue Origin, Virgin Galactic and SpaceX hint at a future of space exploration no longer dependent on taxpayers alone. Late last year, NASA announced that it was moving ahead with plans to offer a docking port and other resources to companies interested in adding a commercial module to the ISS.

"While NASA prepares for the transition from the Space Station to its successors, the agency is also working to support and grow the community of scientists and entrepreneurs conducting research and growing businesses in space," officials wrote in October. "A vibrant user community will be key to ensuring the economic viability of future space stations."

Aldrin's plan for getting humans to Mars is one he's been working on for decades. It involves the development of spacecraft called "Mars cyclers," which would perform perpetual cycling orbits between the Earth and the moon. Thanks to assists from the gravitational forces of both planetary bodies, minimal propellant would be needed, freeing up critical space for cargo and astronauts.

You can see a demonstration of how the cyclers would move through our solar system below:

"The foundation of human transportation is the cycler," Aldrin told the conference audience. "Very rugged, so it'll last 30 years or so; no external moving parts."

It's estimated that a trip to Mars from Earth aboard a cycler would average five and a half months. A return trip from a twin cycler would take an equal amount of time. Put enough cyclers in the rotation, however, and you gradually create, as Aldrin called it, a "subway-in-the-sky between our planet and our future second home."

Whatever means of transportation eventually places boots on the Martian surface, Aldrin is adamant that we at least make every effort to stay there.

"Let's be certain that we've developed a sustainable plan to stay on Mars," he said. "No flags and footprints this time."

Michael d'Estries ( @michaeldestries ) covers science, technology, art, and the beautiful, unusual corners of our incredible world.