Sometimes, retreating to the dryness and security of a landlubber's lab is the best way to understand what's happening on a planet far, far away. For instance, when the Phoenix spacecraft landed on Mars in 2008, it kicked up enough dust to reveal water ice--a surprise to its builders, who hadn't thought that the lander's relatively weak rocket engines could have moved so much material. To find out what happened, astrophysicists at NASA's Ames facility devised an artificial environment full of crushed walnut shells to test the engines and found that the pulsing of the rockets on the Martian surface injected more gas into the soil than expected. The gas then burst out of the soil in explosive puffs, causing erosion.