The Sciences

To Hitch a Ride to Mars, Just Flag Down an Asteroid

DiscoblogBy Patrick MorganFeb 11, 2011 4:44 PM

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Mars missions should probably come with the kind of warning label you'd find on a cigarette pack: "May cause cancer and blindness." If you were traveling to Mars solely by spacecraft, your health might take a serious hit during the 18-month or so round-trip journey--and you might not even be able to see your home by the time you got back. Throughout the journey, high-energy particles known as cosmic rays would course through your body, not only damaging your eyesight, but also increasing your risk of cancer by up to 20 percent. Luckily, one scientist has an answer: Don't fly a spaceship to Mars, hop on an asteroid instead. Cosmic rays zing into our solar system from interstellar space; here on Earth our planet's magnetic field protects us from them, and astronauts aboard the International Space Station are mostly protected by the Earth's bulk and its magnetic field as well. But astronauts on a long-haul trip to Mars would be in more danger. As it stands, our current radiation shields are too cumbersome for spacecraft, and light-weight aluminum shields can exacerbate the problem: Cosmic rays can reflect off the metal and create secondary radiation. Hence, the asteroid plan, which Douglas Adams would surely approve of. In his paper, which is set to be published in Acta Astronautica next month, Gregory Matloff of New York City College of Technology suggests that a Mars-bound spacecraft could settle down on an asteroid for the duration of the trip. By parking in a crater or tunneling into the asteroid's surface, astronauts would be shielded from cosmic rays by the craggy rock. Matoff explains that the asteroid should be at least 33 feet wide, and also notes that it would help if it passed by both Earth and Mars. That 33-foot width is based off density measurements of the Ida and Mathilde asteroids, and assumes that spacecraft will be able to bore into a roughly spherical asteroid to escape the cosmic rays, Matloff says. "If our space crew digs in 5 meters [16.4 feet], they have enough shielding from asteroid material," he adds. "For a spherical asteroid, they will be at the center of a 10-meter or 33-foot sphere." That magic number, Matoff says, is a conservative estimate. "We could probably work with a smaller near earth object (NEO)." If the asteroid were porous, the width would have to be larger than 33 feet, and if the asteroid were especially iron-rich, the necessary width would be smaller. It turns out that there are at least five asteroids passing from Earth to Mars in the next 90 years. But since it would take five years for the space rocks to orbit around Mars on its way back to Earth, the astronauts would be stranded for a bit. Matloff has an answer to this too. As National Geographic reports:

Ideally, astronauts would divert an asteroid so that it cycles permanently between Earth and Mars on a well-timed orbit. Humans could nudge an asteroid into the desired path using a solar sail or gentle propulsion.... Once the asteroid is in a stable orbit, Matloff said, "you'd just jump on it. You could store provisions and spare parts on it and use it for shielding.... "

But other scientists believe this asteroid-riding business is way too complicated. From National Geographic:

Nasser Barghouty, a project scientist at NASA's Space Radiation Shielding Project, said Matloff's idea works in theory. But he thinks having so many extra launches and landings would prove too risky.... Like an airline passenger with multiple layovers, "I'd need to hop on so many legs [during the journey]," he said. "That adds to the complexity of the mission, which adds more risk."

The future, according to Barghouty, lies in plastics, which are light-weight and could shield a spacecraft from radiation--but are also a thoroughly anticlimactic option when compared to latching on to a space rock that's hurtling through the solar system. Given the choice between plastics and hitching a ride on an asteroid, I think I'll go with the rock. Related Content: 80beats: The Real Problem With a Human Trip to Mars: Radiation 80beats: Would A Mission to Mars Drive Astronauts Insane? Six Earth-Bound Volunteers Aim to Find Out. 80beats: Traveling to Mars? You'll Need This Miniature Magnetic Force-Field DISCOVER: Russia's Dark Horse Plan to Get to Mars DISCOVER: 11 Space Missions That Will Make Headlines in 2011 (photo gallery)

Image: flickr / andrewsrj

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