Mars exploration. Hang on! Curiosity is plunging onto Mars.

Mars ExplorationNASA has $2.5 billion riding on the success of the Curiosity rover's scary-new "sky-crane" landing system designed by engineers at NASA's Jet Propulsion Laboratory. If Curiosity crashes as it dangles by cables from its flying platform festooned with blazing rockets, some scientists will see a decade or more of their careers crash with it. But there's even more riding on Curiosity's safe touchdown on 5 August. Not only will NASA have to slow the most massive load ever delivered to another planet's surface from hypervelocity bullet speeds to a dead stop, all in the usual "7 minutes of terror." But NASA is also attempting to deliver Curiosity to the surface of Mars more precisely than any mission before, within a 20-kilometer-long ellipse some 240 million kilometers from Earth. Both feats are essential to NASA's long-term goals at Mars: returning samples of martian rock and sending humans to the Red Planet.