NASA's New Target

Far beyond the Moon

Forty-one years ago, a scientist at Northrop (now Northrop Grumman) proposed using moon rockets to go to an asteroid. In some ways, NASA's latest plan is similar; it too relies on spacecraft designed for lunar travel-the vehicles belonging to the Constellation program, which NASA is building to replace the shuttle and then go to the moon and beyond.

But although the hardware is similar, an asteroid mission couldn't be more different from a trip to the moon. Actually, an asteroid mission has one clear advantage: The virtually negligible gravity at the crew's destination means they need less fuel to get home.

That lack of gravity, however, means that the first person to reach an asteroid will not take one giant leap for mankind, and he will not drive a dune buggy. "You're going to be wearing a backpack and flying around," says Rusty Schweickart, an Apollo 9 astronaut who is now chairman of the B612 Foundation, whose goal is "to significantly alter the orbit of an asteroid, in a controlled manner, by 2015." Astronauts might explore the asteroid from inside their spacecraft using remotely controlled instruments, or they might anchor their spacecraft to the surface of the asteroid by firing hooks into the object and reeling themselves in.

The biggest logistical hurdle is the sheer distance involved. It takes a few days to travel the 238,855 miles to the moon, but it will take more than a month to cover the distance of up to 4.5 million miles separating us from just about any asteroid of interest. The crew of two or three will live in their small quarters for several months. Psychological experiments and historical precedent show that isolation and boredom can mentally break an otherwise sane person; NASA will have to find a way to keep an asteroid-bound crew from losing their minds. It will also have to engineer a means to shelter the astronauts from the intense cosmic radiation found outside the protection of Earth's magnetic field.

Most ominously, though, there's this little wrinkle: If anything goes wrong out there for an asteroid-bound space traveler, there's almost no chance of rescue.

Destination: Unknown

Which asteroids would we visit? "You need an asteroid that's in an orbit very similar to the orbit of the Earth," says David Morrison, a senior scientist at the NASA Astrobiology Institute. "There aren't many, so we would be quite dependent on carrying out a new survey." The ideal target asteroid will also be at least a couple hundred meters in diameter, will have a very slow rotation of 10 hours or more, and will have the potential to come too close to Earth for comfort. Scientists suspect approximately 1,000 asteroids meet these criteria-but we have yet to find them.

In 2005, Congress ordered NASA to develop a program to detect, track, catalog, and characterize, by the end of 2020, 90 percent of all near-Earth objects (an expanded category that includes comets as well as asteroids) 140 meters in diameter and larger. The hitch: Right now, NASA doesn't have the budget to get it done by that deadline.

The interplay between Congress and NASA brings up the more terrestrial matter of politics. The stated goal of President George Bush's administration is to launch an "extended" moon mission by 2020 and, later, to build a permanent moon base that could function as a springboard for a manned mission to Mars. That could all change after next year's election, however. A new administration could divert money from human space exploration to any number of other projects-say, satellite-based climate science. "I don't think that the Vision"-the Bush administration's plan for a new era of human space exploration-"as written today is likely to survive the election, even if a Republican is elected," says Robert Zubrin, president of the Mars Society.

Then again, some experts believe the Constellation program will move forward no matter who wins in '08; if it doesn't, NASA won't have any spacecraft after the shuttle retires. And although the feasibility study doesn't mean we're headed to an asteroid soon, it does tell us that if we decide to go, we can get there. So if, say, we find one day that we need to visit 99942 Apophis to find the best way to knock it off a collision course with Earth, or if we need a refueling station for astronauts headed for Mars, we might be in luck.

Dawn Stover is PopSci's editor at large. She lives in White Salmon, Washington, where she has a clear view of the night skies.