Scientific American Instant Egghead NASA’s latest Mars rover, called Curiosity, is huge. It’s almost ten feet long, seven feet tall, and it weighs nearly a ton. You can think of it as a 2.5 billion dollar smart car. So, how do you park something like that on Mars? To start, you’ve got to slow it down. On August 5th or 6th, depending on your time zone, Curiosity will hit the Martian atmosphere at nearly twenty times the speed of a bullet. Seven minutes later, it’ll be resting on the surface. At least, that’s the plan. Landing on Mars gently takes a well-choreographed sequence of EDL: that’s Entry, Descent, and Landing. But, NASA is the best in the business when it comes to reaching Mars. Since the mid-1970s, the US has landed six robots safely, and only lost one. Let’s look at how they do it. The first step in EDL is E, Entry. Curiosity will enter the Martian atmosphere at about thirteen thousand miles per hour. Even though the planet’s atmosphere is thin, it’s still enough to create plenty of friction on an inbound spacecraft. Like its predecessors, Curiosity will use a thermal shield to absorb heat from the friction. This will slow it way down to about nine hundred miles per hour. At an altitude of seven miles, it’s time for the next stage of EDL: Descent. The spacecraft will deploy a parachute fifty feet across. This will slow the capsule down to about two hundred miles per hour. Once Curiosity reaches about a mile above the surface of Mars, the parachute detaches and landing rockets take over. Now, Curiosity is in unexplored territory. Past Mars missions, such as the Phoenix lander and the Viking landers of the 1970s have gone all the way down to the surface on their rockets. Other landers, such as Mars Pathfinder, and the Spirit and Opportunity rovers, have bounced to the surface in protective airbags. But, Curiosity is so big it requires a new approach. The rockets will take it most of the way down to the surface. Then, a sky crane takes over, easing the rover down on tethers. That’s the L in EDL, Landing. Once Curiosity is resting on its own six wheels, the rocket power platform detaches and flies away. Then, Curiosity is free to explore the Martian landscape. If it sounds awfully complex, that’s because it is. But, NASA has 2.5 billion dollars that says it ought to work. For Scientific American Instant Egghead, I’m John Matson.