Kent Rominger has spent more than 1,600 hr. in space, all in low Earth orbit. The two-time shuttle commander has a host of memories on which to reflect, including how unbelievably fast the coast of Florida receded as he soared aloft on his first launch. But it was his first look in the other direction that really sticks in his mind.

“The most incredible thing I’ve ever seen is the color looking out into space—and that color is black—a black so dark, so stark, so vast, I’d never seen anything like it before,” he recalls. “And then it dawned on me, well, it is not the color, it is not the black that is so captivating. What I was really appreciating was the vastness of space. Without the atmosphere, I could tell I was looking trillions and trillions of miles into the depths of space, and it really struck me.”

That vastness, that sense of possibility that has drawn explorers like Rominger since the first protohumans wandered out of Africa an instant ago in cosmic time—or millions of Earth orbits around the Sun—is the backdrop to the push to go beyond this planet that began with Yuri Gagarin’s launch in 1961. It continued last month when an American, a Russian and a German lifted off from that same pad in Kazakhstan for the International Space Station (photo).

Maxim Suraev, Alexander Gerst and Reid Wiseman reached their destination 6 hr. later. That is as deep into space as humans have gone—with the exception of a few flights to the Hubble Space Telescope and other slightly higher targets in low Earth orbit—since Apollo 17 started its return trip from the Moon Dec. 14, 1972.

The space station is the engineering marvel of our age—a spaceship the length of a football field where six people conduct cutting-edge scientific research while refining our collective skill at operating above the atmosphere. But the space agencies of the world do not agree on where we should go next with that hard-won expertise. There are not that many choices, and the few that there are will not be easy. Mars, it seems, is as far as humankind can practicably expect to go, for now.

“Based on limitations to human physiology, based on reasonable technical limitations to the ability to shield humans during long voyages in interplanetary space, the horizon goal for human space exploration is Mars,” says Jonathan Lunine, a top planetary scientist at Cornell University, who co-chaired the recent U.S. National Research Council (NRC) human-spaceflight study. “Now, horizon in this case essentially means the farthest goal. It is not the only goal.”

Nor will it be cheap. Ultimately, the NRC panel found, the human exploration of Mars will take “decades” of work, and cost “hundreds of billions” of dollars. No one has that kind of money—not the U.S., not China and not, in the foreseeable future, all of the spacefaring nations and wannabees put together.

“I would not want to indulge in specious precision to say whether it was $300 billion or $500 billion, but it is a lot of money,” says John C. Sommerer, a retired Applied Physics Laboratory engineer who headed the subcommittee that drafted the technical portion of the NRC report. “Given that we currently spend on the order of $8 billion [annually in the U.S.] on human spaceflight, you immediately understand why it is a long-term program.”

Although humans are getting a robot’s-eye view of the Martian surface every day, courtesy of the Curiosity rover (see page 40), no one even pretends there will be a human landing there until the 2030s at the earliest. Most of the world’s space agencies include Mars in their exploration plans, but only NASA treats it as a viable goal toward which work is ongoing now that is designed to make it happen.

Like the U.S. space program from its earliest days, NASA’s latest plan is a product of pragmatism, pork-barrel politics and some brilliant engineering. There is also an element of blarney—Administrator Charles Bolden says it will take only “a modest increase” in funding to land humans on Mars in 20 years or so, following the path NASA has cobbled together since the Obama administration ordered a course change five years ago (AW&ST April 28, p. 20).

That has since been amended to funding “consistent with economic growth.” The NRC panel, and many other skeptics, would beg to differ. But Bolden—who commanded the shuttle mission that went deeper into space than any other to put the Hubble Space Telescope in orbit—is right on target when he says Congress isn’t going to give the space program almost 4% of the federal budget, as it did during the Cold War race to the Moon. He is also right when he says “we are farther down the road [to deep space] than we have been for a long, long, long time.”

The articles that follow help pinpoint where that is.