The team responsible for the MARSIS radar instrument on Mars Express has advised the ESA to put off the deployment of its radar booms. Currently, the booms are folded up like accordions against the side of the spacecraft, and they're designed to spring into 20-metre hollow cylinders. New and improved computer simulations show that they could swing more wildly when deployed than originally predicted, and potentially damage parts of the spacecraft. MARSIS will study the sub-surface of Mars to a depth of a few kilometres, and should reveal underground reservoirs of water or ice.