SpaceX, Elon Musk's poster child of the commercial space travel revolution, is about to attempt the first ever soft landing of a heavy space launch vehicle. On March 16, SpaceX mission CRS-3 will lift off from Cape Canaveral on a resupply mission to the International Space Station. Usually, the massive primary stage of the rocket would fall into the Atlantic ocean after launch -- but in this case, it will sprout some metal legs and use what's left of its rocket fuel to slowly return to Earth. This is perhaps the single most important step in SpaceX's stated goal of reducing the cost of space travel by a factor of 10, eventually leading to the human colonization of Mars.