In a news conference last month, John Grunsfeld, head of NASA’s science directorate, admitted that he and his colleagues were anxious about what would happen when the $2.5 billion rover named Curiosity descended onto Mars. “This is risky business,” he said, with a proud little smile. We know today that everything worked out all right—the one-ton robot landed safely on Mars, exactly as planned—but don’t let that fool you into thinking that any fretting in the halls of NASA and the Jet Propulsion Laboratory had been overblown. Curiosity represented a giant step forward in our technological prowess in space.

To see how the robot did its thing, check out this animated video JPL produced, or this one. They explain Curiosity’s remarkable landing method, in which the rover was lowered by parachute and a thin “sky crane” right into place. This was required because the robot was too big to be bounced onto the ground with air bags, the method used for previous rovers. The landing wasn’t the only ingenious thing: for the next two years, Curiosity will be going further and doing more than previous Mars explorers have, firing lasers at rocks and analyzing their contents as part of a quest to determine whether Mars ever might have supported life.

One striking and humbling thing about Curiosity is that this is nothing compared to what will be required if our civilization-scale dreams of human exploration or even settlement of Mars are to come to fruition. Set aside for now all the questions of how humans would live on Mars: even the landing itself has to be figured out. It was a huge achievement to get a one-ton rover onto Mars today. To get humans and all the gear necessary to support them will require a lander that weighs 10 or 20 times as much. NASA says the sky crane won’t work for that.