I thought I'd follow up last month's post on the US plans for a manned mission to a near-Earth asteroid with a link to an article by Wired Science's Laura Sanders. Landing on an asteroid's a good idea, but which asteroid do you pick?
[R]esearchers have begun culling the list of potential candidates. Martin Elvis of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, proposed criteria for identifying “potentially visitable objects” on April 28 in Brookline, Massachusetts, at a meeting of the American Astronomical Society’s Division on Dynamical Astronomy.
Asteroids come in a menagerie of sizes, shapes and trajectories. Some are little more than giant loose rubble piles, while others are densely packed. Though Obama’s proposal didn’t point to any specific destinations, Elvis says that a worthy asteroid ought to have a few key features, including a slow spin rate, no problematic satellites and a solar orbit that allows for a long and recurring launch window.
“Are they spinning rapidly? Are they elongated? Is there strange, irregular gravity?” Elvis asks. If the asteroid is “lumpy and nasty, that’s not good.”
The most important consideration, though, is that the asteroid is easy to get to. While the majority of asteroids reside in a belt between the orbits of Mars and Jupiter, some come close to Earth. A relatively nearby asteroid that circles the sun at a speed similar to the Earth’s would be ideal, Elvis reported. So far, six of 6,699 known near-Earth asteroids seem to have amenable orbits.
For many researchers, the visit will be a mini–Mars-mission — a chance to test strategies and equipment before traveling to the red planet. A round-trip journey to a nearby asteroid might take about half a year. A mission to Mars would take more than twice as long.
“If you want to climb Mount Everest, you don’t climb K2 first,” says astronaut and astronomer John Grunsfeld of the Space Telescope Science Institute in Baltimore. Practicing deep space maneuvers on a nearby asteroid would be like climbing Washington’s Mount Rainier before tackling the Himalayas.