4. Missions to Mars …
Many scientists think Mars, which has large underground glaciers, could be our best bet for a permanent colony on another planet. But the obstacles to living there are daunting. Humans can’t breathe the air, and the planet’s frequent dust storms would make farming difficult. Solar radiation is another problem, and sending messages to Earth (via radio waves traveling at the speed of light) can take more than 20 minutes, depending on where the planets are in their orbits.
Still, scientists, architects, and engineers are brainstorming ways to overcome those obstacles. ZA Architects, a Ukrainian firm, has drawn up plans for structures made out of Martian soil; robots could be sent ahead to build them. Other researchers propose inhabiting Mars’s lava tubes—underground caverns likely formed by volcanoes—since the tunnels also provide protection from solar radiation and dust storms and would keep the temperature relatively constant. And NASA is testing an inflatable habitat that could be deployed on the surface of Mars.
If a group of humans were to live on Mars for centuries with little or no contact with Earth, they would likely evolve, eventually becoming a different species, Impey told me. Because Mars has less gravity, scientists believe humans would slowly grow taller and their cardiovascular systems would become weaker. They’d also have less body hair (because they’d have to stay indoors or wear space suits, they wouldn’t need the protection from the elements), and their controlled diet might result in smaller teeth. But that’s assuming, of course, that humans can reproduce in Mars’s gravity—an untested proposition.
5. ... And Beyond
In or near the moon’s orbit, there exist a few spots, called Lagrange points, where an object is pulled neither to the moon nor to Earth. A space station orbiting one of these points could stay in place for a long time without floating away.
Eventually, Pat Troutman told me, one of those areas could serve as a harbor for ships going out farther into the universe, a sort of Rotterdam of the solar system. Resupplying and refueling would be costly from Earth, but, aided by robots, astronauts could pull a large boulder from an asteroid, tow it to a stable area, and mine it for water and oxygen, which could be turned into rocket propellant, Troutman said.
The dwarf planet Ceres, the largest object in the asteroid belt, may have big reserves of water, making it a potential base for more refueling, Troutman told me. And if Mars turns out to be uninhabitable, the Jovian system—Jupiter and its moons—might be a good alternative, he said. It, too, has water, and is largely protected from the sun’s radiation.
The universe contains an almost incomprehensible number of stars—our galaxy alone has hundreds of billions, and there exist hundreds of billions of galaxies—and an even greater number of planets. Current technology isn’t very good at determining which of those planets might be habitable—or already inhabited, Sara Seager, a professor of planetary science and physics at MIT, told me. But our view of the galaxy could become a little clearer in 2018 with the launch of the $9 billion James Webb Space Telescope. It will sit 1 million miles from Earth, where it will search for gases that look out of place in the atmospheres of other planets, signaling vapors that might be produced by other life-forms.