Mars looms large as a human destination in sci-fi lore—no surprise, given that it remains unmarred by human boot prints but orbits the sun tantalizingly close to Earth, well within the realm of possible exploration. But that possibility has always been out of reach.
If that changes, it likely won't be for another two decades at the very least. Obama has stated that his goal is to send U.S. astronauts on a round-trip swing past Mars in the 2030s, with a landing on the Red Planet shortly thereafter.
Reaching Mars might require extensive international cooperation—or some creative thinking. Some nations have already joined forces for robotic exploration of the planet or to lay groundwork for a future manned mission. China's first Mars probe, Yinghuo 1, is expected to hitch a ride to the Red Planet as early as this year on a Russian rocket along with Phobos–Grunt, a Russian lander bound for Phobos, one of the two tiny Martian moons.
And Russia has already partnered with the European Space Agency (ESA) to investigate the psychological effects that the prolonged confinement and isolation of a round-trip Mars journey might have on a crew. In an experiment called Mars500, now in progress, six volunteers are spending more than 500 days in an enclosed capsule in Moscow, punctuated by a simulated landing and spacewalk on Mars.
But serious technical challenges and physiological questions remain. (For one, can a human safely endure the dosage of cosmic radiation that comes with such a journey?). And at present, no nation is close to being able to send a manned mission to Mars, let alone return that crew safely.
Enter the creative thinking: Some, including physicist Lawrence Krauss, have proposed that the best way to get to Mars might be to make it a one-way trip. That would greatly reduce the complexity of the mission—no need for a return stage, no need for fuel for the trip home—and cut in half the dangerous cosmic radiation dosage that astronauts would accrue on the interplanetary journey.
In 2009, after taking office, Obama convened a blue-ribbon panel to review NASA's plans for manned spaceflight. One of that commission's suggestions was a manned mission to a Lagrange point in space, one of five gravitational equilibrium points in the sun–Earth system where gravitational and centrifugal forces balance to create a relatively stable place to essentially hover in a deep-space orbit. (Astronauts would not be able to explore much while spacewalking at a Lagrange point, but it would be an unprecedented voyage into deep space nonetheless.)
One of those points, a spot well beyond the orbit of the moon known as L2, has become a popular destination for unmanned astronomical spacecraft—both NASA and ESA have sent missions there.
The L5 Society, a 1970s group driven by the space-colonization ideas of Princeton University professor Gerard O'Neill, advocated for a human presence at the two most stable Lagrange points, L4 and L5. That dream has not yet become reality but may in the coming decades as humankind ventures beyond low Earth orbit and into ever deeper reaches of the solar system.