Imagine trying to land an SUV-sized rover on another world. That's definitely enough of a challenge on its own, but picture doing so while the rover hangs perilously beneath a hovering sky crane, connected by just a handful of clothesline-like nylon cables.
Within minutes and with no external help, the spacecraft must slow down from 13,000 mph (21,000 kph) to zero, ensuring that the sky crane gently lowers the rover onto the surface wheels-first, ready to conduct the science mission it was designed for. You only have one shot at the landing, during which the Red Planet's rotation will spin the rover out of view of Earth, preventing you from directly communicating with it — and learning of its success or failure — for a brief but agonizing stretch.
